Glue, Gelatine, Animal Charcoal, Phosphorous, Cements, Pastes and Mucilages

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Title: Glue, Gelatine, Animal Charcoal, Phosphorous, Cements, Pastes and Mucilages
Author: Dawidowsky, F.
Language: English
As this book started as an ASCII text book there are no pictures available.

*** Start of this LibraryBlog Digital Book "Glue, Gelatine, Animal Charcoal, Phosphorous, Cements, Pastes and Mucilages" ***

GLUE, GELATINE, ANIMAL CHARCOAL,
PHOSPHORUS, CEMENTS, PASTES,
AND MUCILAGES,

COMPRISING

THE RAW MATERIALS AND MANUFACTURE OF SKIN AND BONE GLUE,
DIFFERENT VARIETIES OF GLUE, ANIMAL CHARCOAL, PHOSPHORUS,
GELATINE AND PRODUCTS PREPARED FROM IT; ISINGLASS AND
FISH-GLUE, METHODS OF TESTING GLUE AND GELATINE,
AND THE PREPARATION AND APPLICATION OF
CEMENTS, PASTES AND MUCILAGES FOR USE
IN THE WORKSHOP, LABORATORY,
AND OFFICE.

BY
F. DAWIDOWSKY,
TECHNICAL CHEMIST.

EDITED FROM THE GERMAN, WITH EXTENSIVE ADDITIONS, INCLUDING
A DESCRIPTION OF THE MOST RECENT PROCESSES.

BY
WILLIAM T. BRANNT,
EDITOR OF “THE TECHNO-CHEMICAL RECEIPT BOOK.”

ILLUSTRATED BY FIFTY-NINE ENGRAVINGS.

SECOND EDITION, REVISED AND LARGELY RE-WRITTEN.

PHILADELPHIA:
HENRY CAREY BAIRD & CO.,
INDUSTRIAL PUBLISHERS, BOOKSELLERS AND IMPORTERS,
810 WALNUT STREET.
1905.

PRINTED BY THE
WICKERSHAM PRINTING CO.,
53 and 55 North Queen Street,
LANCASTER, PA., U. S. A.

PREFACE TO THE SECOND EDITION.

The first edition of this work has been out of print for some years,
but nevertheless there is a constant demand for it, and this together
with the fact that frequent inquiries are received for information in
this department of industry, are the inducements which have led to the
preparation of the present treatise.

The book is arranged in two parts, Part I. comprising Glue, Gelatine
and Allied Products, and Part II. Cements, Pastes and Mucilages, and it
is fully illustrated with engravings of various types of apparatus.

Since the appearance of the first edition much progress has been made
in the manufacture of glue and allied products. Old and wasteful
methods of working have been replaced by more approved processes, and
in the present volume it has been endeavored to place before those
interested in these industries, a practical and comprehensive account
of modern methods of operation.

In order adequately to represent this advancement and development, the
best authorities have been freely consulted and drawn upon, special
acknowledgments being due to the following works: “Bone Products and
Manures,” by Thomas Lambert, and “Glue and Glue Testing,” by Samuel
Rideal.

As the demand for phosphorus is steadily increasing, and the
manufacture of this product from bones and bone-ash forms an important
branch of the utilization of bones, it has been deemed advisable to
devote a chapter to this subject.

The receipts for cements, pastes, and mucilages given in Part II.
have been gathered from numerous sources. They have been critically
examined, and are offered, with the full conviction, that they will not
be found wanting in efficacy.

The Table of Contents and Index have both been carefully prepared, and
being very full, will make reference to any subject in the volume easy
and satisfactory.

W. T. B.

PHILADELPHIA, PA., AUGUST 10, 1905.

CONTENTS.

PART I.

GLUE AND GELATINE.

CHAPTER I.

NATURE of GLUE.

PAGE

Sources of glue; Change in the animal tissues by continued boiling;
Definition of what is known as glue; Most important glue-yielding
substances 1

Transformations of which glue and gelatine are the products;
Transition stages of glue; Production of the glue-yielding substance
of the animal body 2

Crude glue and jelly; Constitution of glue; Combinations of which glue
consists 3

Preparation of pure glutin; Properties of glutin 4

Preparation and properties of chondrin 5

Adhesive power of glutin and of chondrin; Properties of glue and its
behavior towards other substances; Quantity of glutin in glue 6

Properties of jelly before drying to glue; Absorption of ozone by the
jelly; Behavior of glue solution towards different salts; Effect of
acids upon glue; Meta-gelatin 7

Combinations of tannin with the jelly; Effects of dry heat upon glue;
Chemical composition of glue and glue-yielding substance 8

CHAPTER II.

USES of GLUE.

Glue as a joining medium, and requirements for this purpose 10

Glue as a binding agent; Consumption of glue in the manufacture of
matches 11

Quality of glue required by bookbinders; Glue in sizing; Glue for
culinary and medicinal purposes 12

Glue for clarifying and fining beer, wine and other liquids; Bouillon
tablets; Glue as a healing agent 13

Glue for elastic masses and a partial substitute for rubber; Use of
glue in photolithography; Hectograph mass; Glue for fancy articles 14

Gelatine veneers and their uses 15

CHAPTER III.

RAW MATERIALS AND THEIR PREPARATION FOR THE MANUFACTURE OF GLUE.

Principal substances employed for the manufacture of glue; Division of
raw materials into groups 16

Animal skin and its constitution 17

Portion of the skin of value for the manufacture of leather and glue;
Yield of glue from tannery waste; Influence of the age of the animals
from which the skins have been derived upon the quality of the
glue 18

Notes in reference to judging glue-stock 19

Liming of waste 20

Precaution and care required when buying glue leather; Arrangements
required for the preparation of glue stock; Location of the glue
factory; Lime pits; Contrivances for washing the limed stock 21

Washing drums; Pits or vats with proper arrangements for stirring,
draining and inspection; Glue stock washer invented by W. A.
Hoeveller, described and illustrated 22

Sheds for storing and sorting; Mode of carrying on the work in the
factory; Liming; Preparation of milk of lime 26

Importance of the quality of the lime used; Testing the value of a
lime by determining the amount of real calcium hydroxide contained in
it; Mode of conducting the operation 27

Washing the material after removal from the lime pit; Washing and
drying 28

Preservation of the glue-stock by means of carbolic acid; Preparation
of carbolic acid solution for this purpose 29

Use of other antiseptics for the purpose of preventing putrefaction;
Formaldehyde and boric acid; Classification of the principal varieties
of hides and leather for glue-stock 30

Bones and cartilages 31

Constitution of bones; Composition of bone cartilage; Value of bones
for the manufacture of glue; Necessity of exercising care in buying
bones 32

Sorting the bones; Crushing or grinding the bones 33

Stamping mill for crushing bones, described and illustrated 34

Bone crusher, described and illustrated; Crosskill bone mill,
described and illustrated; Sieve for sorting the crushed bones,
described and illustrated 36

Lime bath for bones; Treatment of the bones with hydrochloric
acid 37

Washing the stock; Use of dilute sulphurous acid in place of
hydrochloric acid as suggested by Gerland; Jullion and Pirie’s process
for the preparation of gelatine from bones 38

Leather waste; Mechanical manipulation of the waste; Comminution of
the waste and use of a rag-engine or hollander for this
purpose 39

Various methods of extracting tannin from leather waste 40

Raw materials for fish glue; Difference between isinglass and glue
manufactured from entire fishes; Principal points to be observed in
the manufacture of fish glue 41

Utilization of scales of large fishes 42

CHAPTER IV.

MANUFACTURE OF SKIN GLUE.

Classification of operations; Definition of crude glue; Derivation of
the bulk of this stock 43

Cooking or boiling glue-stock; Boiler for this purpose, and manner of
using it 44

Duration of boiling 45

Mode of ascertaining the progress of the operation; Convenient
apparatus for glue-boiling with water, described and
illustrated 46

Extracting the glue stock by the use of steam 47

Boiler for this purpose, described and illustrated; Use of
open-jacketed pans heated by steam, described and illustrated 49

Process of cooking as described by Mr. Thomas Lambert; Terne’s glue
boiler, described and illustrated 51

Clarifying the glue-liquor 52

Distinction between clearness and color; Clarifying vats; Prevention
of putrefaction of the liquor 53

Use of alum and other chemicals for clarifying; Freeing the liquor
from coloring substances 54

Use of animal charcoal for this purpose; Bleaching the raw materials
previous to boiling them to glue; Use of chloride of lime or of
sulphurous acid for this purpose 55

Forming or moulding the glue; Moulds for this purpose 56

Detaching the glue from the sides of the moulding boxes; Cutting the
cubes of glue into commercial cakes or sheets; On what the shape of
the cakes depends 57

Use of stone-slabs in place of cooling boxes; Use of glass or zinc
plates for liquors which in gelatinizing do not become very
solid 58

Tools for cutting the jelly into cakes, described and
illustrated 59

Machine for slicing and spreading glue-jelly preparatory to drying
invented by Mr. J. Schneible, described and illustrated 60

Cutting apparatus patented by M. Devoulx, described and
illustrated 62

Drying the cakes of glue; Drying in the open air; Mode of conducting
the operation in a drying room 64

Size of the drying room; Circulation and change of air in the drying
room 65

Nets and frames for drying the glue; Objections to twine
netting 66

Metallic netting and its advantages; Regulation of the temperature of
the drying room; Means of promoting the dryness of the air 67

Use of long drying galleries; Apparatus for drying glue, invented by
W. A. Hoeveller, described and illustrated 68

Modern drying house, described and illustrated 71

Method to accelerate the drying of glue, proposed by Fleck 72

Mode of giving the dry cakes a good lustrous appearance 73

CHAPTER V.

MANUFACTURE OF BONE GLUE.

Comminution of the bones; Various methods of extracting the fat;
Boiling bones 74

Steaming bones and apparatus for this purpose 75

Extraction of bones with benzine or carbon disulphide; Apparatus for
the use of benzine invented by Messrs. Wm. Adamson and Charles F. A.
Simonis of Philadelphia, Pa., described and illustrated 76

Adamson’s method for treating substances with hydrocarbon vapor for
the purpose of extracting oils, fats, etc., described and
illustrated 79

Adamson’s method for treating substances with liquid hydrocarbon for
the purpose of extracting oils, fats, etc., described and
illustrated 82

Adamson’s process for removing hydrocarbons from substances which
have been treated therewith, described and illustrated 84

F. Seltsam’s apparatus, described and illustrated 86

F. Seltsam’s apparatus as improved by Th. Richter, described and
illustrated 88

Alfred Leuner’s apparatus, described and illustrated 90

Extraction with hydrochloric acid 91

Sulphurous acid process 92

Generation of sulphurous acid 93

Apparatus for the generation of sulphurous acid constructed by Dr.
Bruno Terne, described and illustrated; Conversion of cartilage into
glue; Wm. Friedberg’s apparatus for this purpose, described and
illustrated 94

Mode of operation with this apparatus 95

Construction of the filter used in connection with the
apparatus 96

Settling tank, described and illustrated; Arrangement of an open
evaporating pan, described and illustrated 98

Cooling the glue liquor; Use of refrigerating machines for that
purpose; Spiral evaporators 100

Vacuum pan for evaporating glue and gelatine liquors, described and
illustrated 101

Instrument which indicates the amount of dry glue in the solution,
described and illustrated 103

Process for the simultaneous utilization of bones for fat, bone-meal
and glue 104

Crushing the bones; Apparatus for subjecting the crushed bones to the
action of high-pressure steam, described and illustrated 105

Mode of operation with this apparatus 106

Duration of steaming the bones for the manufacture of animal
charcoal 107

Sorting the bones for the manufacture of animal charcoal; Former
method of carbonization 108

Arrangement of a Belgian retort-furnace, described and
illustrated 109

Products evolved in the destructive distillation of bones; Mode of
operation with Belgian retort-furnaces 112

Products obtained in making animal charcoal on a large scale; Process
for the simultaneous utilization of the bones for fat, glue and
calcium phosphate; Degreasing the bones 113

Treatment of the bones with hydrochloric acid; Preservation of the
resulting cartilage; Boiling the cartilage in open vessels 114

Mode of extracting the phosphates from bones; Yield of glue obtained
from cartilage after extraction of the mineral constituents;
Constituents of the liquor obtained by treating the bones 115

Utilization of the liquor in the manufacture of fertilizers 116

CHAPTER VI.

MANUFACTURE OF PHOSPHORUS.

Operations included in the ordinary method of preparing phosphorus;
Burning the bones to ash; Kiln used for this purpose 117

Improved form of kiln proposed by Fleck; Mode of operation with a kiln
of this construction 118

Quantity of substance which remains after burning the bones;
Composition of bone ash; Conversion of the bone ash into a coarse
powder; Decomposition of the bone ash by sulphuric acid 119

Separate processes which have to be distinguished; Embodiment of these
processes in equations 120

Actual yield of phosphorus; Methods by which the formation of calcium
phosphate may be effected; Process without the assistance of
heat 121

Decomposition of the bone ash in the warm way 122

Apparatus for hot lixiviation 123

Evaporation of the liquor; Mixing the fluid with charcoal 124

Yield of so-called distilling mass; Utilization of the liquor obtained
in treating bones for the manufacture of glue with hydrochloric acid;
Concentration of the liquor for crystallization 125

Mode of obtaining the calcium phosphate contained in the
mother-liquor; Drying the crystals 126

Mixing the crystals with charcoal; Evaporating pans; Treatment of
the residue of basic calcium phosphate left in the manufacture of
phosphorus; Distillation of the phosphorus; Conversion of the acid
calcium phosphate into calcium metaphosphate and reduction of the
latter; Retorts and furnace for distilling the mixture of acid
calcium phosphate and charcoal; The galley-furnace 127

Modification of the galley-furnace, described and
illustrated 128

Furnaces for the use of coke as fuel; Receivers for collecting the
phosphorus distilling over 129

Process of distillation; Indication of the commencement of
distillation 130

Removing the phosphorus from the receivers; Regaining the phosphoric
acid contained in the water from the receivers; Constitution of crude
phosphorus 131

Refining and purifying the phosphorus; Various methods of
purification; Percentage of loss of phosphorus 132

Distillation of the crude product in order to obtain pure phosphorus;
Retorts and distilling apparatus for this purpose, described and
illustrated 133

Process of distillation; Different qualities of the phosphorus
passing over in the various stages of distillation; Separation of the
phosphorus passing over according to quality 134

Moulding the refined phosphorus; Seubert’s apparatus for this
purpose 135

Disadvantages of Seubert’s apparatus; Improved apparatus by which
the operation is rendered perfectly free from danger, described and
illustrated 136

Moulding the phosphorus in wedge-shaped sheet-metal boxes 137

Mode of storing and shipping phosphorus; Manufacture of phosphorus
with the assistance of electricity; Mixture used for the
operation 138

Furnace employed for the electrolytic manufacture of phosphorus,
described and illustrated 139

Mode of operating the furnace 140

CHAPTER VII.

METHODS OF BLEACHING GLUE.

Bleaching in the air; Bleaching with chlorine 141

Bleaching with animal charcoal 142

Bleaching with sulphurous acid; Apparatus for the production of the
acid solution, described and illustrated 143

CHAPTER VIII.

DIFFERENT VARIETIES OF GLUE AND THEIR PREPARATION.

Joiner’s glue; Material for the best variety of joiner’s glue 146

How to make and use glue; Holding power of glue 147

Cologne glue 148

Russian glue; Additions by means of which the color and opaqueness are
imparted to this variety of glue 149

Patent glue; Gilder’s glue; Superior article of gilder’s glue; Size
glue and parchment glue; Paris glue 150

Liquid glues; Receipts for liquid glues 151

Preparation of saccharate of lime; Steam-glue; Russian steam-glue;
Pale steam-glue; Dark steam-glue 152

Chrome glue; Glue for attaching leather to metal; Glue for leather,
paper, etc. 153

Glue for parchment paper in making sausage skins 154

Tungstic glue; Indestructible mass for the manufacture of ornaments,
toys, etc.; Compound for billiard balls 155

Coloring glue; Process for this purpose invented by G. J. Lesser 156

Composition for printing rollers; Size 157

Process used in an English factory for making tub-size 158

Preparation of bone-size; Composition of the different grades
of size 159

Concentrated size; Bookbinder’s size; Water-proof glue; Glue solution
for rendering wrapping paper water-proof 160

Water-proofing fabrics with glue and tannin 161

Muratori and Landry’s process of water-proofing fabrics 162

Muzmann and Krakowitzer’s process of water-proofing fabrics; Glue for
joints in leather driving belts; Hectograph mass 163

Formulas for hectograph masses 164

CHAPTER IX.

MANUFACTURE OF GELATINE, AND PRODUCTS PREPARED FROM IT.

Properties of gelatine; Change in the chemical constitution of
gelatine produced by concentrated sulphuric or nitric acid; Tannin as
a test for the presence of gelatine; Use of gelatine for culinary and
medicinal purposes 165

Skin gelatine; Method of manufacture introduced and patented, in 1839,
by George Nelson; Process patented, in 1844, by Messrs. J. & G.
Cox of Edinburgh 166

G. P. Swinborn’s improved patented process for the preparation
of gelatine from hides, skins and glue pieces; Modern process of
preparing skin gelatine; “Steeping” the skins 167

Washing and bleaching the skins 168

Digesting the skins; Clarifying the liquors 169

Evaporation of the liquors in vacuo; Drying the cut cakes; Bone
gelatine; Materials for this purpose; Crushing the bones; Solution of
the glue cartilage 170

Apparatus and improved manner of manufacture employed in the factory
of D. J. Briers, described and illustrated 171

Modern process of preparing bone gelatine 179

Colored gelatine; Uses of colored gelatine; Harmless coloring matters;
Colors for coloring leaves of gelatine with aniline colors for
technical purposes 181

Gelatine for fining purposes; _Gelatine Lainée_; Fining powder for
wine and beer; Liquid fining gelatine; Preparation of gelatine from
ordinary glue 182

Preparation of gelatine for photographic printing and for photographic
purposes in general; Removal of the salts from the gelatine 183

Gelatine capsules for medicinal purposes; Court plaster 184

Gelatine foils; Mode of coloring the foils 185

Gelatine veneers; Principal operations in the manufacture of gelatine
veneers 186

Preparation of the plates; Preparation of the glue solutions;
Proportions by weight of the mixtures for ten different varieties of
imitations of marble and enamel 187

Imitation of mother-of-pearl veneers 188

Pouring the colored solutions of glue upon the plates 189

Preparation of imitations of malachite 190

Transferring the layer of glue to a layer of gelatine 191

Drying and detaching the veneers 192

Water-proofing gelatine veneers; Uses of gelatine veneers;
Formo-gelatine and its uses 193

Use of gelatine in bacteriology 194

Artificial silk from gelatine 195

CHAPTER X.

ISINGLASS AND ITS SUBSTITUTES.

Sources of isinglass; Properties of a good quality of isinglass;
Imitations of isinglass and their detection; Adulteration of isinglass
and its detection 196

Russian isinglass; Siberian purse isinglass; Preparation of isinglass
in Russia 197

North American or New York isinglass 198

East India isinglass; Hudson Bay isinglass; Brazilian isinglass 199

German isinglass; Isinglass from the scales of shad and herring;
Bleaching inferior qualities of isinglass; Ichthycolle
Française 200

Isinglassine; Chinese isinglass 201

Irish moss; Fish glue; Jennings’ process for the preparation of fish
glue 203

Treatment of fish scales; Production of fish glue on the Norwegian
coast; Substitute for isinglass according to C. A. Sahlström’s
process 203

Whale glue 204

CHAPTER XI.

TESTING GLUE AND GELATINE.

Determination of moisture; Determination of ash; Determination of
acidity 205

Determination of glutin; Bisler-Beumat’s method 206

Analysis of samples of American glue by S. Dana Hayes; Deduction of
the quality of glue from indirect properties 207

Lipowitz’s method of testing the strength of a glue, described and
illustrated 208

Results obtained by comparative experiments 209

Facts shown by the results 210

Weidenbusch’s method of testing glue 211

Preparation of the plaster of Paris stick and of the glue solution
used in this test 212

Apparatus for testing the strength of the plaster of Paris sticks,
described and illustrated; Test adopted by the “Artillerie Werkstätte”
at Spandau 213

Determination of adulterations 214

Kissling’s results in testing a large number of samples of glue 215

Practical tests of glue 216

PART II.

CEMENTS, PASTES, MUCILAGES.

CHAPTER XII.

CLASSIFICATION OF CEMENTS.

Stohmann’s division of cements and pastes; Groups of cements 218

Chemical nature of cements; Oil cements 219

Resinous cements; Definition of resins 220

Properties of resinous cements 221

Rubber and gutta-percha cements; Glue and starch cements 222

Lime cements 223

CHAPTER XIII.

PREPARATION OF CEMENTS, PASTES, AND MUCILAGES.

Oil cements; Putty and its preparation 224

French putty; Soft putty; Litharge cement; Red lead cement; Cement
for wash basins 225

Zinc-white cement; Mastic cement, mastic or _pierres de mastic_ 226

French mastic; Paget’s mastic; Water-proof cement; Serbat’s
mastic 227

Stephen’s oil cement; Oil cement for glass; Oil cement free from lead
for steam pipes; Oil cements for steam pipes; Oil cement for
marble 228

Oil cement for porcelain; Diamond cement; Hager’s diamond cement;
Resinous cements; Resinous cement for amber; Cement for
turners 229

Cement for ivory and bone; Cement for white enameled clock faces;
Cements for glass; Cement for glass upon glass; Cement for glass upon
metal; Cement for metal letters upon glass; Cement for wood 230

Cement for knife handles; Cement for petroleum lamps; Cement for
porcelain; Cement for porcelain which is to be heated; Cement to
withstand the action of petroleum; Cement for mica 231

Cement for horn, whalebone and tortoise shell; Cement for terra cotta
articles; Mastic cement for glass; Stick mastic cement; Sulphur cement
for porcelain 232

Insoluble cement for wooden vessels; Rubber cements; Cements for glass;
Soft rubber cement 233

Hard rubber cement; Elastic cement; Marine glue 234

Jeffrey’s marine glue; Marine glue for damp walls; Gutta-percha
cements; Cement for leather 235

Cement for hard rubber combs; Elastic gutta-percha cement; Cement for
horses’ hoofs; Cement for crockery 236

Cement for leather; Caseine cements; Preparation of pure caseine 237

Preparation of ordinary technical caseine; John A. Just’s method for
obtaining a purer technical caseine 238

Caseine cement which can be kept for a long time; Cement for glass;
Cement for metals; Cement for porcelain; Cement for meerschaum;
Cement for wood, etc. 239

Cement for porcelain; Water-glass and water-glass cements; Water-glass
and its properties; Cement for cracked bottles 240

Cement for glass and porcelain; Cement for hydraulic works; Cement for
uniting metals; Cement for tightening joints of pipes exposed to a red
heat 241

Cement for marble and alabaster; Glycerine and glycerine cements;
Properties of commercial glycerine; Glycerine and litharge cement 242

Lime cements; Properties of lime and chalk; Cement for glass; Cement
for joiners; Cement for cracked clay crucibles and porcelain 243

Lime and glue cement; Gypsum cements; Preparation of plaster of Paris;
Cement for plaster of Paris statues 244

Cement for glass and porcelain; Cement for iron and stone; Cements
for porcelain; Universal plaster of Paris cement; Iron cements;
Heat-resisting cement; Water and steam-proof cement; Cement for
iron 245

Fire-proof cement for iron pipes; Cements resisting high temperatures;
Cement for filling in defects in castings; Cement for cracked
stove-plates, etc.; Cement for iron water-tanks; Cement for cracked
iron pots 246

Black cement for stoves; Cements for chemical apparatus; Requirements
of such cements; Cement for small apparatus to be used for the
development of fluoric acid 247

Linseed oil and clay cement; Linseed oil and manganese cement; Cements
resisting very high temperatures; Cement resisting acids; Rubber
cement for chemical apparatus 248

Scheibler’s cement for chemical apparatus; Cements for special purposes;
Cement for attaching metal letters to glass, marble, wood, etc.; Cement
for joints of iron pipes 249

Steam boiler cement; Cement for rubber; Cement for tires; Cement for
steam pipes, etc. 250

Cement for marble; Cement for attaching wood, glass, etc., to metal;
Brushmaker’s cement; Cement for electrical apparatus 251

Jeweler’s cement; American cement for jewelers; Cement for celluloid;
Stratena; Cement for cloth; How to use cements 252

Importance of bringing the cement into intimate contact with the
surface to be united 253

Obstacles to the junction of any two surfaces; Importance of using as
little cement as possible 254

Cleansing surfaces to be joined from grease and dirt; Paste and
mucilages; Starch paste 255

Rules for preparing paste; Flour paste 256

Means to prevent the spoiling of paste 257

Shoemakers’ paste 258

Gum arabic and its properties; Dextrine and its use in place of gum
arabic; Properties of commercial dextrine 259

Preparation of dextrine; Blumenthal’s method 260

Heuzé’s method; Tragacanth, or gum tragacanth; Pastes and mucilages
for special purposes; Starch paste; Flour paste 261

Strong adhesive paste; Paste that will not sour; Venetian paste 262

Label paste; Elastic or pliable paste; Mucilage for labels;
Mucilage 263

Mucilage for postage stamps; Caseine mucilage; Tragacanth mucilage;
Adhesive paste; Fluid pastes 264

Sugar and lime paste; Liquid sugar and lime paste; Pastes for paper and
fine fancy articles; Albumen paste 265

Glycerine paste; Paste for fixing labels on machines; Paste for
mounting maps; Paste for fastening paper on tin-foil; Paste for paper
bags; Caseine mucilage for photographer’s use; Paste for scrap
books 266

Paste for skins; Strong mucilage capable of fastening wood on china
and glass; Dextrine mucilage; Paste for joining leather to
pasteboard 267

Paste for attaching labels to polished nickel; Mucilage for attaching
labels to tin; Mucilage for office use; Glycerine paste for office
use; Clean and durable paste 268

Banknote or mouth glue; Paste for cardboard; Paste for attaching cloth
or leather to table tops; Caseine mucilage; Very adhesive paste which
may be used for wood and parchment 269

Paste for pads; Paste for fastening paper on tin-foil; Paste for
attaching labels to glass, porcelain and metal; Preparation of
arabol-gum; Preparation of an adhesive substance from desaccharized
beet-root slices 270

Index 273

GLUE, GELATINE, CEMENTS, PASTES.

PART I.

GLUE AND GELATINE.

CHAPTER I.

NATURE OF GLUE.

1. SOURCES OF GLUE.

The organisms of all animals, but more especially of the higher
classes, contain tissues which are insoluble in cold, as well as in
hot, water. However, by continued boiling they become dissolved, and
yield on evaporation of the solution a glutinous, gelatinizing mass. By
further drying this mass exhibits, according to the degree of purity
of the material, a more or less transparent and brittle substance,
which in its pure state is devoid of color as well as of smell; it
swells up in cold water and dissolves by boiling in that liquid. This
substance, _i. e._, the product of the conversion of the so-called glue
or gelatine-yielding tissue, is what is known in the trade as _glue_.

Among the glue-yielding tissues, the following are the most important:
Cellular tissue, the corium, tendons or sinews, the middle membrane of
the vasa lymphatica and veins, the ossein or organic matter of bones,
hartshorn, cartilage, the air bladders of many kinds of fishes, etc.

Neither glue nor gelatine exists ready formed in the animal organism,
except under abnormal conditions as a phenomenon of disease, but they
are the products of various transformations. The first of these
transformations evidently takes place in drying the hide, since the
result of boiling to glue a green hide prepared in the usual manner by
liming, etc., but not previously dried, will be an entirely different
product of less consistency than that obtained by drying the hide after
liming and then boiling. A second transformation seems to take place
in boiling the material, and a third in drying the jelly obtained, and
this may explain the fact that the latter, which is not converted into
actual glue, differs in its behavior from glue solution. The series
of transformation does not end even with the actual glue, for it is a
well-known fact that glue dissolved in water and boiled for some time
does not gelatinize on cooling, but remains liquid. We have here to
deal with organic combinations which are distinguished from the more
solid organic compounds by passing more readily into decomposition.
However, it is an established fact that glue is an organic combination
presenting itself in different modifications. In the animal organism
it occurs ready formed only under abnormal conditions as a phenomenon
of disease, and hence it is only produced by first drying and then
by continued boiling of the glue-yielding substance, and finally by
evaporating and further drying the gelatinous mass obtained by boiling.

2. TRANSITION STAGES OF GLUE.

We therefore distinguish:

_a._ Glue-yielding substance.

_b._ Crude glue.

_c._ Jelly.

_d._ Glue.

_a._ The glue-yielding substance of the animal body is produced from
proteïne substances, albumen, fibrine and caseïne, in a manner similar
to that in which new substances are formed in the ripening fruit by
the transformation and disintegration into constituent parts of others
previously present.

_b._ By _crude glue_ are understood glue-yielding materials free from
all foreign matter and physically prepared by drying. It forms an
intermediate link between glue-yielding substance and jelly.

This distinction between glue-yielding substance and crude glue is
justified by experience. If, for instance, fresh calves’ heads, such as
the tanner cuts off after swelling the skins, be carefully limed and
then boiled without previous drying, the result will be a turbid liquor
containing, though everything be dissolved, no jelly whatever, or at
least, very little.

_c._ _Jelly_ is obtained by boiling the crude glue. Its adhesive power
is far less than that of solution of finished glue, and it will become
more quickly putrid than the latter.

_d._ The finished product _glue_ is, in most cases, not a definite
chemical compound, but a mixture of substances, with two of which
scientific research has made us thoroughly acquainted.

3. CONSTITUTION OF GLUE.

Independent of impurities and accidental constituents, glue consists
of two distinctly distinguishable combinations, namely, _glutin or
gelatin_ and _chondrin_, the former being formed from the hide and
osseous parts, and the latter from young bones while still in a soft
state, and the “permanent” cartilages, such as those of the ribs and
joints.

The manufacturer has it, of course, in his power to allow either of
these substances to predominate in his product, but since experiments
have shown glutin or gelatin to possess much greater adhesive power
than chondrin, it is advisable to separate as much as possible the
cartilaginous matter from other glue-yielding material.

As an accurate knowledge of these constituents of glue is of great
importance to the manufacturer, brief reference will here be made to
what scientific research has made known to us in regard to them.

Pure glutin or gelatin is obtained by treating buckshorn, etc., with
water containing hydrochloric acid, until the phosphate of lime which
serves, so to say, as a frame for the glue-yielding substance, is
dissolved, and the organic tissue called _collagen_ or _ossein_,
remains behind. After freeing the latter from fat by steeping in milk
of lime and careful washing, it is boiled, and the resulting jelly,
when cold, mechanically distributed in cold water, in which it softens
but does not dissolve. By thoroughly stirring the mass the glutin
yields its coloring matter to the water, the latter being replaced
by fresh water until all the coloring matter is extracted. Then pour
off the water and after dissolving the jelly in hot water, filter the
solution through a cloth. By mixing the filtered solution with an
equal volume of alcohol, a precipitate of pure glutin is obtained. By
the precipitation with alcohol, the separating glutin carries down
inorganic salts, especially phosphates, which may be present in the
solution. To free it from them, dissolve it in a small quantity of
lukewarm water, acidulate the solution with hydrochloric acid and bring
it into a dialyser. The salts and the acids diffuse in the water which
has from time to time to be renewed, and finally a jelly of pure glutin
remains behind; this is evaporated to dryness in shallow vessels.

Pure glutin, in a dry state forms a glassy substance, almost colorless,
transparent to translucent, brittle or slightly elastic, free from odor
and taste, and remains unchanged in the air. Its specific gravity is
greater than that of water. It is neutral, exerts no influence whatever
upon vegetable colors and is insoluble in alcohol, ether, hydrocarbons
or oils. In cold water it swells up, absorbing as much as 40 per cent.,
and becomes opaque, but does not dissolve. It dissolves in hot water
and on cooling forms a jelly even if the solution contains only 1 per
cent. of glutin. It gelatinizes at a lower temperature than chondrin.

An aqueous solution of glutin is precipitated by chlorine, platinic
chloride, tannin and alcohol, but not by hydrochloric acid,
acetic acid, lead acetate, alum and ferric sulphate. Concentrated
sulphuric acid decomposes glutin, forming, besides other products of
decomposition, chiefly glycocoll and leucine.

When heated, glutin softens, swells and diffuses an odor of burnt
hartshorn. In the air, it takes fire with difficulty, smokes, flames
only for a few minutes, and leaves a bulky charcoal difficult to
incinerate, the ashes of which consist principally of calcium phosphate.

Glutin, when in the jellied state, and treated with alcohol, undergoes
dehydration, under the influence of which it contracts greatly. It was
by this means that Gonnor succeeded in reducing in a remarkable degree
the size of a print obtained in a very hydrated film of glutin, and
transferring it, so reduced, to stone, from which he obtained a new
impression, quite similar to the first, but more or less diminished.

By taking these prints, on the contrary, with glutin very little
hydrated, and afterwards steeping them in water, a dilatation of the
plate is obtained, which enlarges the figures with the same regularity.

Pure _chondrin_ is prepared by boiling for from 24 to 48 hours the
cartilages of the ribs, of the larynx with the exception of those of
the epiglot, or of the windpipe and the bronchi.

Chondrin is precipitated from its solution by alcohol. The precipitate
is redissolved in warm water, evaporated, and dried. It forms a
semi-translucent mass of a slightly yellow color and resembles glutin
as regards fracture and all external properties, but differs from it in
being precipitated from its aqueous solution by mineral acids, acetate
of lead, alum and ferric sulphate, and also by organic acids such as
vinegar, citric and oxalic acids, none of which precipitate glutin.

As regards its chemical composition, chondrin is poorer in nitrogen
than glutin, and contains more sulphur. Its formula approaches more
closely that of albumen, which corresponds also with the origin of
chondrin, for cartilages may be considered as transition-links between
the proteïne and glue-yielding substances.

By the action of concentrated sulphuric acid upon chondrin, leucine
is only produced but no glycocoll. By potassium hydrate chondrin is
converted into glutin and yields then, like the latter, leucine and
glycocoll. By boiling with concentrated hydrochloric acid chondrin is
decomposed; a peculiar variety of fermentable sugar, to which the term
chondroglucose has been applied, being formed.

It may finally be remarked that chondrin possesses less adhesive power
than glutin and its presence in glue may be considered detrimental. To
avoid its formation, the glue manufacturer should separate as much as
possible cartilages from bones. Chondrin, however, is useful for size.

4. PROPERTIES OF GLUE AND ITS BEHAVIOR TOWARDS OTHER SUBSTANCES.

The product designated by the general term glue, is always a mixture of
glutin, chondrin and other substances not yet accurately determined.
Glue is formed by evaporating and further drying the jelly, and its
properties depend on the crude glue and glue-yielding material used for
the production of the jelly.

It may here be remarked that even if the quantity of glutin contained
in the different products could not be determined by scientific means,
the glue obtained from various materials can be readily distinguished
by external characteristics. Every manufacturer knows that hides and
bones yield a distinct quality of glue as regards adhesive power,
elasticity and fracture, and that the jelly from glue-yielding
substances of older animals is more solid and gives a larger yield than
that obtained from the tissues of younger and weaker animals. Glue from
the bladders and scales of fishes, though consisting mainly of glutin,
differs materially from hide or bone glue.

Generally speaking, the jelly, no matter whether consisting of glutin
or chondrin, possesses, before drying to glue, different properties
from glue solution. It has less adhesive power and spoils more quickly.
At a temperature of 68° to 72.5° F., jelly putrefies inside of 24
hours, smells of ammonia, and decomposes, while glue solution can be
kept much longer without suffering deterioration.

The jelly absorbs ozone with avidity and is decomposed by it, this
being the reason why an approaching thunderstorm may cause great damage
by destroying the coagulating power of the glue liquors, or causing the
glue to turn on the nets, _i. e._, to lose its consistency and become
liquid and foul.

The behavior of glue solution towards different salts also deserves
attention.

By adding potassium or sodium carbonate, neutral potassium tartrate,
Rochelle or Epsom salts to a lukewarm fluid containing 15 to 20 per
cent. of glue, the latter coagulates by the salt withdrawing the water
from it. A lukewarm solution saturated with common salt, sal ammoniac,
saltpetre, or barium chloride does not gelatinize.

By adding to glue solution a large quantity of alum, the glue is
precipitated as a transparent mass.

Glue compounded at a high temperature with dilute acids, does not
gelatinize by itself, but will do so on adding common salt.

Boiling with slaked lime deprives glue solution of its power of
gelatinizing, and, on evaporation, changes it into a colorless gummy
mass which is soluble in cold water and in saturated solution of common
salt.

From a glutin solution compounded with oxalic acid, the latter can
after some time be again separated by the addition of lime, the result
being a non-gelatinizing fluid which, however, possesses great adhesive
power. This is the so-called _meta-gelatin_.

Glue solution also loses its property of gelatinizing by repeated
boiling and cooling (for about six days).

Tannin enters with the jelly, as well as with glue solution, into
characteristic combinations which are formed even in solutions
containing only 0.005 per cent. of jelly or glue. Glue is, therefore,
an excellent agent for the detection of tannin.

When quite concentrated glue solution is treated with tannin, a heavy,
flocculent precipitate of a dirty-yellow, caseous character is formed,
which turns brown on exposure to the air and, after drying, constitutes
a hard brittle mass, easily reduced to powder and soluble in hot potash
lye, but insoluble in water, ether and alcohol. This precipitate, if
not identical with, is closely allied to the combination of tannin with
skin, called leather.

Glue exposed to a dry heat melts, diffuses a strong disagreeable odor
of burned horn and leaves behind a charcoal which has a powerful
discoloring effect like animal charcoal. When subjected to destructive
distillation, glue yields an aqueous solution of ammonium carbonate
and a thick brown oil consisting of a mixture of ammonium carbonate,
sulphur, ammonium cyanide, etc.

The chemical composition of glue is such as to bring to mind that of
starch and cellulose derived from the vegetable kingdom. It contains:

Carbon 49.1 per cent.
Hydrogen 6.5 per cent.
Nitrogen 18.3 per cent.
Oxygen and sulphur 26.1 per cent.

which may be represented by the formula: C_{12}H_{10}N_{2}O_{4}.

The composition of glue differs but little from that of the
glue-yielding substance. Isinglass is composed of:

Carbon 49.5 per cent.
Hydrogen 6.9 per cent.
Nitrogen 18.8 per cent.
Oxygen 24.8 per cent.

This justifies the assumption that glue in its various transition
stages does not represent different chemical combinations, but only
modifications of one and the same combination distinguishable from each
other by physical characteristics, as is the case with starch, which
without suffering an alteration in its composition, appears as dextrine
and grape-sugar, or as with cellulose, which, without altering its
composition, can be transformed into amyloid and grape-sugar.

CHAPTER II.

USES OF GLUE.

An inquiry into the various technical uses of glue must be of interest
to the manufacturer so as to enable him, when acting, as is frequently
the case, as salesman, to know to whom to offer his product; and also
to learn what special demands he has to satisfy, as not every glue
is adapted to every purpose, different qualities being required for
special uses.

_Glue as a joining medium._ In Chapter I, treating of the nature of
glue, special attention has been drawn to the fact, that the adhesive
power of glutin is greater than that of chondrin; and that glutin
obtained from skin and tendons possesses still greater adhesive power
than the product from bones. This is the reason why good sound glue
made from scraps of skin is preferred by those artisans who may be
considered the principal consumers, such as cabinet-makers, carpenters,
turners, instrument-makers, wood-carvers, carriage-builders,
brush-manufacturers, bookbinders, paper-manufacturers, etc., all
of them requiring glue of the greatest possible adhesive power. It
must, however, by no means be understood that a good quality of bone
glue cannot be used for the same purposes; because much bone glue of
excellent quality and at a low price is brought into the market by
manufacturers of animal charcoal and bone meal, and is used in glueing
wood, etc.

Glue suitable as a joining medium for the above purposes should be of
an amber or brown-yellow color, transparent or translucent, clear, dry
and hard, and show a glassy fracture which should not be brittle, but
somewhat elastic. Placed in cold water it should swell up and absorb
as much of it as possible without actually dissolving, even if it
remains there for 48 hours. The supernatant water should be free from
a putrid odor and contain but a small quantity of foreign substances
in solution. Such glue passes into solution at 122° F., and dissolves
entirely on heating to 144.5° F. Heating to a higher temperature should
be avoided.

_Glue as a binding agent._ Glue solution is used for bind-together
pulverulent substances, such as mineral colors in the manufacture of
colored paper and paper-hangings, in painting in distemper, in the
size of the gilder; or it is mixed with plaster of Paris or chalk for
the manufacture of plastic masses which become hard on drying, such
as stucco-work, papier-maché, etc. Generally speaking, it is best to
use only good sound glue for these purposes, though it may sometimes
be possible to utilize defective and cheap qualities without injurious
consequences. For color mixtures, the glue should at all events be
free from acids and alkalies, as they exert a decomposing and altering
effect upon the colors. The gilder should always use the best quality
of glue, as otherwise the work he applies later on to the size will
spoil.

A very large quantity of glue is consumed _in the manufacture of
matches_, and much depends on its quality and drying properties. The
dipping composition for matches containing phosphorus is a bath of
glue of 25 to 50 per cent. strength to which the requisite amount of
an oxidizing agent, like potassium nitrate or chlorate has been added,
kept at a temperature of 100.4° F. The phosphorus is cautiously put
in; it melts, and is stirred to an emulsion, when the sand, glass or
other friction-agent is incorporated. The object of the glue is to
protect from oxidation, without diminishing the sensitiveness. Glue is
also used as the binding material in the heads and rubbers of safety
matches.

_Book binders_ require for the better classes of work a glue which
should naturally be pale and strong, and without marked odor. Some
inferior glues which have been chemically bleached turn almost black in
the pot, owing to the bleaching agent not having been properly removed
or neutralized.

Sand, glass and emery papers and cloths are made by coating the surface
with a thin uniform layer of strong glue, and sifting the powder evenly
on.

_Glue in sizing._ The principal object of sizing goods is to impart to
them a certain degree of stiffness, to give them a nice appearance and
a good feel.

As glue would injure the color of white goods, it cannot be used for
sizing them, but, on the other hand, much is employed for preparing
size for the use of hat and cloth manufacturers, weavers, etc. Before
the introduction of the paper machine and invention of rosin glue,
animal glue was exclusively used for sizing paper, but at the present
it is only used for sizing paper manufactured from rags, and for
pasteboard, and also by manufacturers producing drawing paper sized
with animal substances. The paper, after leaving the machine, is passed
through a glue solution and then dried in the air.

For actual sizing purposes good and fine varieties of glue are only
used, or sometimes the manufacturers prepare their own size by boiling
to glue dried calves’ heads, or rabbit skins deprived of their fur,
scraps of parchment, etc. For cheap woollen hats, glue is used in place
of shellac. The cloth manufacturer procures his glue mostly in the form
of a jelly. This variety of glue deserves special attention and the
mode of preparing it will be referred to later on.

_Glue for culinary and medicinal purposes._ The use of glue for these
purposes is based upon three properties:

1: Upon its power of coagulating and inclosing while in this state,
substances mechanically dissolved and finely divided in a fluid, which,
being specifically as heavy as the fluid itself, render the latter
turbid and cannot be got rid off by settling. The glue in this case
acts as a clarifier.

Large quantities of isinglass and gelatine, specially prepared for
the purpose, are used for clarifying and fining beer, wine and other
liquids, as well as for preparing jellies. The material to be used for
jellies and other culinary purposes must, of course, be colorless and
entirely free from odor. Jellies are made palatable by flavoring with
spices, sugar, essences, etc., before congealing, A vegetable gelatine,
Agar-Agar, which will be referred to later on is now brought from
China, and being cheaper and perfectly free from odor, has become quite
a competitor with isinglass and gelatine.

Prior to the introduction of Liebig’s and other beef extracts, bouillon
tablets, consisting of a mixture of bone-jelly, meat broth, extract
of pot herbs and flour, were largely used. One hundred and ten pounds
of meat repeatedly boiled yield five pounds of bouillon tablets. A
good meat broth, though not equal to that from Liebig’s or other meat
extracts, is obtained from these tablets by the addition of thirty
times their weight of water.

If glue be dissolved in water, it gelatinizes at the ordinary
temperature, and if the solution be mixed with other fluids, for
instance, meat broth, fruit juices and essences, which in the form of
jelly are to serve as food, it effects their solidification.

Glue acts as a healing agent by preventing the access of air to
wounds. Court plaster is prepared from gelatine. When cabinet-makers
cut themselves, they apply glue to the wound with the best success.
In hospitals a compound of gelatine and glycerine is used as the
best means of closing wounds, the same compound having also been
successfully used for preserving articles of food such as eggs, fruit,
and even meat.

Every good quality of glue can be used for the above purposes.

Medicines of a disagreeable taste are frequently inclosed in gelatine
capsules, so that they can be taken without causing inconvenience to
the patient. The use of these capsules has grown to such an extent as
to form a special branch of industry. The mode of manufacturing them
will be described later on.

_Glue for elastic masses and as a partial substitute for rubber._ Glue
mixed with glycerine forms an elastic mass resembling rubber. The
same effect can be produced by an addition of molasses. This elastic
mass, the preparation of which will be described later on, is of great
importance for the manufacture of printers’ rollers, for moulds, etc.
Some manufacturers prepare the mass ready for use, so that the printer
or lithographer need only remelt it, and cast it in a mould.

Glue is of great importance in photolithography as, mixed with chromium
salts, it is the only known means of transferring a photographic
negative to the stone. In photography, gelatine is used for negative
pictures upon glass. For the manufacturer of casts of plaster of Paris
or cement, this glue mass, which is generally used without an addition
of glycerine, is indispensable for making moulds which are much
undercut.

Glue mixed with glycerine may be used as a substitute for rubber in
manufacturing elastic toys, such as dolls’ heads, animals, etc. For
these purposes it is advisable to select glue which forms a very solid
jelly, even if it possesses but little adhesive power, pure bone-glue
being the best.

Glue mixed with glycerine (1 part glue, 1 part glycerine) is used as
hectograph mass for the transfer of matter written with concentrated
solution of aniline color.

_Glue for fancy articles._ Great progress has been made in the use of
glue and gelatine in the manufacture of fancy articles.

The best known of all these products are perhaps the gelatine foils.
They form thin, transparent sheets, brilliantly colored, and are used
for printing sacred images, visiting cards, labels, etc.

Gelatine veneers were first shown at one of the Paris International
Exhibitions. They consist of sheets varying in thickness, which
have been deprived of their translucency by an admixture of colors
in imitation of various crystallization of salts, and such stones
as lazulite, malachite and avanturine. Glue imitations of mother of
pearl, tortoise shell, and ivory were shown which closely resembled the
genuine articles. These veneers have been largely introduced in the
manufacture of fancy articles, cabinet ware, buttons, etc. The most
brilliant use to which they have been put is in the manufacture of
fans, for which ivory and tortoise shell were formerly used, and there
are perhaps few ladies that are aware that these glittering toys are
manufactured from horse bones from the knacker’s yard.

The successful introduction of gelatine veneers was soon followed by a
substitute for horn in general, and combs, buttons, snuff-boxes, and
hundreds of other fancy articles have been manufactured from these
imitations.

In the foregoing statement only some of the principal uses of glue have
been enumerated, and there can be no doubt that with an increase in the
knowledge of its nature and properties, a wide field is still open for
progress in this industry.

CHAPTER III.

RAW MATERIALS AND THEIR PREPARATION FOR THE MANUFACTURE OF GLUE.

The raw materials used for the manufacture of glue consist of a variety
of animal offal. The principal substances employed are refuse from
tanyards, such as scraps of ox and other thick hides, the waste of the
workshops of leather dressers, morocco leather manufacturers, etc. The
tendons and intestines of many animals, rabbit and hare skins deprived
of their fur, cat and dog skins, scraps of parchment, waste of turners
and button makers, and offal from butcher shops and households, help to
swell the series of materials used for the manufacture of glue.

The materials are collected and sold either directly to the glue
boiler, or to dealers making a specialty of glue stock.

As a thorough knowledge of these waste products is of importance to
the manufacturer, this chapter will be devoted to their detailed
description, the success of the enterprise depending largely on
the selection of the raw materials and their careful sorting and
preparation. By bearing in mind the varied products—from the most
ordinary black glue to the colorless glassy gelatine for photographic
and culinary purposes—it will be understood that entirely different
raw materials have to be employed for the finer products than for the
ordinary qualities of glue.

According to their derivation the raw materials may be divided into
three groups, namely:

1. Skin-like raw materials: Skin, leather, tissues.

2. Bone raw materials.

3. Materials obtained from fishes: Air bladders, scales, etc.

1. ANIMAL SKIN.

[Illustration: FIG. 1.]

This consists of three layers, namely: 1. The thin upper-skin—the
epidermis—which consists only of cellular tissue, and is of no special
importance for the manufacture of glue. 2. The actual leather-skin, or
corium, which consists of fibres of connective tissue and forms the
actual object of the tanner as well as of the glue boiler. Underneath
the corium lies the under-skin, which consists only of cellular tissue
contaminated with particles of flesh and fat, which are detrimental
to the manufacture of glue. Fig. 1 represents a section of the animal
skin. _O_, is the epidermis, _L_, the corium, _U_, the under-skin. The
epidermis consists of two layers. The first, superficial one, _H_, is
known as the cuticle or lamellar layer, and the other deeper layer,
_S_, as the mucous or malpighian layer. The corium also consists of
two layers, the upper one _C_, and the lower one _C_{1}_, which is
the actual leather-skin. The under-skin, _U_, is an elastic tissue
containing many deposits of fat, _F_, and perspiratory glands, _D_,
which are connected with ducts, _D_{1}_, with the surface of the skin.

For the manufacturer of leather and glue, the corium is the only
material of value.

The tanner trims the skins before steeping them in the ooze. From sheep
and calf skins he removes the head portions, it being more advantageous
to use them for glue stock. He also cuts off the skin covering the
lower part of the thighs, and, to give the skin a neat finish, the
ragged edges of the belly part. Of bullock hides, the ears, tails and
foot pieces are utilized for glue stock, while the head parts are
tanned. Such tannery waste may yield 44 to 46 per cent. of glue. Scarf
skin of bullocks’ hides and waste in fleshing the hide, tendons and
hinder parts of cattle yield from 30 to 35 per cent.; horse sinews from
15 to 18 per cent.

Scraps of parchment and bullocks’ feet are highly valued as glue
stock, since they are in fit condition for boiling without further
preparation. They may yield up to 62 per cent. of their weight in glue.

Calf and sheep skins yield a superior glue; that from horse hides is
usually dark and poor in quality, although with careful working a
strong product can be obtained from the latter.

Of great value to the glue boiler are the so-called calves’ heads,
which, after liming and drying, form a special article of commerce.

Skins of hogs, hares and rabbits yield a light-colored glue of little
consistency. It is, therefore, best to use these last-named raw
materials for the preparation of jelly, such as is used in sizing, in
the manufacture of paper, etc.

The older the animals from which the skins have been derived, the more
solid the glue will be. In many cases, especially where a certain
quality of glue is to be produced, it may be recommended to separate
the different kinds of skin refuse into lots, provided there is enough
of each kind to boil it separately.

A considerable number of skins used for packing various articles, such
as indigo from South Africa, have been so much damaged in transit as to
render them useless for tanning, but they form good material for glue,
frequently yielding 50 to 55 per cent.

In reference to judging glue stock some valuable notes are given in
an article on glue, published by the American Provision Co., Chicago,
Ills.:

“Dry, uncured or salted stock, such as raw hide or South American, if
soaked for twelve hours in cold water, gains about 50 per cent. in
weight, and still remains tough, and the water sweet. The moisture,
dirt, and salt should not be over 10 per cent.

“Green salted stock, such as hide pieces, sinews, calf heads and pates,
should have no excess of salt, nor be foul, discolored or heated;
should be tough, with the hair not loose, and have a mild animal odor.
Moisture and salt not over 40 per cent.

“Dry limed stock soaked twelve hours develops a characteristic odor,
and should be firm, fibrous, and have no slimy pieces. The water should
not be dark. Lime, sand and dirt, not over 5 per cent.

“Green limed stock should be smooth and soft, any remaining hair being
easily detachable, while the liquor should be fairly clean, sweet, and
not too alkaline.

“A large quantity of waste bones accumulates in the preparation of
tinned provisions. If these have not been overheated and are in good
condition, a considerable amount of glue can be obtained from them, the
bones of the head, ribs, and feet giving a better yield than those of
the thighs and legs.

“Horn piths should not contain over 12 per cent. moisture, and should
not have been overheated in drying; they should have been cleansed from
skin and hair, which are of little value to the glue-maker.

“The age of the animals yielding glue stock has an important influence
on the product. While from younger animals the product, as a rule, is
of lighter color, more abundant and more easily obtained, it contains
more chondrin, so that from solutions of equal strengths, those from
mature animals will be found to be of greater consistence and the glue
more solid.

“Abroad, dry hides are often, for weighing, soaked in chlorbarium, a
solution of barium chloride, and then in a bath of dilute sulphuric
acid, 1½ per cent., which readily soaks in, combines with the barium
to form the white insoluble powder of barium sulphate, leaving weak
hydrochloric acid in the fibre, to be afterwards neutralized in
liming, the chloride of calcium dissolving out. This treatment affects
considerably the subsequent making of glue, as, beside the effects of
the acids, the sulphate of barium will render the liquors cloudy and
difficult to clarify. Of course if colored glues are to be made this
will be no detriment.”

To prevent putrefaction, which is always accompanied by decomposition
of glue-yielding substance and consequent loss, the scraps must be
carefully preserved, especially in summer.

The tanner prepares the waste by liming, _i. e._, steeping it during
fifteen to twenty days in milk of lime which is frequently renewed.
By the action of the lime, adhering particles of blood and flesh are
dissolved and the fatty matter is saponified. After this treatment the
glue-stock is dried.

In case this work is not done carefully in the tanyard, as is only
too frequently the case, the stock is of but little value to the
glue-boiler.

By allowing the refuse to lie too long in a heap, as is sometimes done,
putrid fermentation sets in, the injurious effects of which cannot be
remedied by subsequent liming, or the lime bath has not yet been strong
enough, or has not acted sufficiently long upon the scraps to destroy
the adhering particles of blood and flesh. The lime bath, on the other
hand, may have been too strong, so as to attack the glue-yielding
substance. Frequently it is also the case that the scraps having been
dried under unfavorable circumstances, mould has commenced to form,
and finally they may be spoiled in winter by allowing them to freeze.
Frozen glue leather yields glue of very little consistency.

It will be seen from the foregoing that great precaution and care are
required when buying glue leather. The manufacturer should especially
see that it is dry and tough, free from mould and all organic and
inorganic substances, and not too strongly limed.

The glue-boiler should, in all cases, be prepared to undertake the
preparation of the glue stock himself. The following arrangements are
required for the purpose:

Let us assume that the glue factory is located on a stream of water. In
the immediate neighborhood of the stream a sufficient number of pits
to prepare all the glue stock used, each about 6½ feet deep and 6½ to
10 feet in diameter, and lined with cement, are so arranged that their
bottoms are about 3 to 3½ feet above the level of the water. They are
supplied with water by means of a pipe line connecting one with the
other. Each pit is provided with a discharge pipe to draw off the dirty
water.

As the glue-stock, before undergoing other operations, has to be
freed from the lime by washing with water, the simplest plan is to
place the limed stock in nets or wicker baskets suspended in running
water by means of a traveling crane or other contrivance erected on
the bank of the stream. This elementary method, however, is open to
several disadvantages, as it fouls a large volume of water and may
lead to legal interference, and its very simplicity is apt to lead to
neglect of precautions, such as brushing away solid particles of lime
or softened animal matters. Further, the great quantities of water
carry off small pieces of glue-stock and fat, if catch-basins are not
provided sufficiently large to allow fat, glue-stock, hair and lime to
separate from the water.

The object is better accomplished and in a shorter time by the use of a
washing drum. This consists of a perforated iron cylinder about 6 feet
in diameter and 4 feet in length, and open on both ends. Around the
inside of the cylinder are fixed a number of wooden shelves 6 inches
broad, which, as the cylinder revolves, carry the glue-stock partly
round, ultimately falling to the bottom again, the movement dashing
it about under a spray of water. In the cylinder is also arranged an
iron plate supported by stays from the outside. While the washing
is in operation the plate is turned perpendicular; on completion it
is brought to a horizontal position, forming a table, on which the
glue-stock falls, and the latter is then removed to a hand-press to
squeeze out the water. The washed stock is then removed to the drying
ground, which should be in a sunny and airy location, and provided with
an inclined floor of planks or cement so arranged as to allow of the
admittance of air from beneath.

As it is well known that small quantities of liquid, frequently renewed
and thoroughly drained off each time, effect the most complete and
economical washing, and in the shortest time, S. Rideal recommends the
use of pits or vats with proper arrangements for stirring, draining and
inspection. The lime scum from the pits can be used in the manufacture
of fertilizers.

The glue-stock washer shown in Figs. 2 to 5, is the invention of W.
A. Hoeveler (American patent), and it relates to the construction of
apparatus for washing glue-stock.

In apparatus for this purpose the stock is very commonly damaged by
being broken up too much, and considerable loss results, besides,
from the fact that the small particles are allowed to escape with the
wash-water. By the present construction and arrangement these defects
are remedied and other advantages derived.

Fig. 2 is a transverse vertical section on line x-x of Fig. 3 of this
apparatus;

[Illustration: FIG. 2.]

Fig. 3 is a longitudinal vertical section of the same;

[Illustration: FIG. 3.]

Fig. 4 is an enlarged plan illustrating the screen and hinged covers,
one being opened and one closed; and

[Illustration: FIG. 4.]

Fig. 5 is a detail of the hub, stems and part of one paddle.

[Illustration: FIG. 5.]

The apparatus is constructed in the form of a rectangular trough-like
structure, with its sides and ends, _A_, substantially water-tight by
means of the double walls, _a a_. The upper portion of the interior is
occupied by the swinging wash-box, _B_, semicircular in shape, with
flat sides and rounded bottom throughout, the bottom being perforated.

Upon a transverse shaft, _c_, journaled at the axis of box, _B_, is set
a paddle-wheel composed of a suitable hub, _d_, and adjustable paddles,
each composed of the radial stem, _e_, and the blade, _f_, or spoon.
The spoons, _f_ are set on the stems, _e_, so as to be capable of being
reversed or turned half-way round, more or less. One side of the spoon,
_f_, is rounded off, so that while passing through the stock the latter
will not cling to or remain upon it. The other side of the spoon is
flat, but slightly skewed or bevelled, so that when turned to face
with the direction of motion of the wheel it not only gathers up the
stock and holds it till out of the box, _B_, but upon further elevation
causes it to roll or slide along the paddle to a predetermined point,
where it falls off gently into a discharge-spout, _g_, which carries it
off for further treatment practically undamaged. During the operation
the box, _B_, and the body, _A_, are kept supplied by a stream of clean
or chemically-prepared water, and the wheel, _e f_, revolves slowly
in the box, the edges of the paddles sweeping around, while the box,
_B_, or its bottom, is kept oscillating, thus preventing an injurious
clogging of the perforations in the box-bottom. After the stock is
placed in the box, _B_, and the latter filled with sufficient water,
the wheel, _e f_, is caused to slowly revolve (by motive or hand
power), with the rounded sides of the spoons, _f_, presented forward.
This operation thoroughly agitates and cleanses the stock, while the
rounded form of the spoons prevents the breaking up of the natural
condition of the stock. The inventor gathers the finer particles as
follows, after they have escaped through the perforated bottom of
the wash-box, _B_. At the lower part of the trough, _A_, elevated on
crossbars or blocks, _h_, he places two parallel strips, _i_, and
between these, which are grooved to form ways, _k_, inside, is set a
long screen, _l_, placed on rollers, _m_, and movable thereby on the
rails or ways, _k_. To give movement to the screen, _l_, the inventor
attaches to its end a rod, _n_, which projects outwardly through the
walls, _a a_, by means of the packing-box, _p_, and cap or door, _q_,
which, when opened, allows the withdrawal of the screen, _l_, and
its burden. The shaking of the screen is accomplished by a suitable
motor applied to rod, _n_, and is kept going during the operation as
required. To the strips, _i_, which are placed at a little distance
from the side walls, _a_ (to leave a passage for the water and refuse
to go through), are hinged the two doors, _r_, which shut down upon
the rod, _s_, as a support, in which case nothing can fall upon the
screen, or which open up and rest against the sides, _a a_, in which
case the screen is exposed and the side passages closed by the doors,
_r_. During the initial or rough-washing stage the doors, _r_, are
kept closed, and the dirty water and refuse pass freely down the side
passages and out at a suitable opening at the bottom. After this stage
it becomes desirable to catch the particles which get detached from the
stock in box, _B_, and come through the perforations therein. Then open
up the doors, _r_, thus closing the side passages and compelling all
the water and small stock to go to the screen, _l_, which catches the
remaining stock. When sufficiently accumulated the screen may be drawn
out and the stock thereon removed. When the main body of stock in box,
_B_, has been cleansed, the paddles or spoons, _f_, are reversed, so as
to present their flat, skewed faces to the stock, and in revolving the
paddles now gently lift the stock and discharge it into the spout or
hopper, _g_. The washing and removal of the stock when washed are thus
accomplished without further manipulation than to reverse the paddles,
which obviously could be done by a reversing-gear on the motor, thereby
reversing the direction of movement of the paddle-wheel.

Instead of the whole box _B_ being oscillated back and forth, its
bottom may be set on slides or rollers and oscillated, while the sides
remain stationary.

In the drawings the box _B_ is shown as hung upon the shaft _c_ as a
centre; but as the provision of means of reciprocating or oscillating
the box or its bottom is within the skill of any machinist, it is not
necessary to describe any specific form. As the box with its contents
will be very heavy, the inventor prefers a special motor for it, which
may also be geared up to reciprocate the screen _l_.

Instead of the door _q_, as located in Fig. 2, it can be located as at
_q’_, same figure.

The entire plant must of course be arranged according to sanitary
regulations, especially as regards river pollution, etc.

The sheds for sorting and storing the glue-stock should, if possible,
be in close proximity to the pits and washing drums, and be dry and
airy. In arranging his plant, the glue manufacturer must, in short,
exercise his ingenuity with a view to carrying on the business with
as little loss of material, and as much saving of time and labor as
possible.

The work in a factory arranged in the above manner, is carried on as
follows:

The raw materials brought by the dealer are weighed, and if in green
state, the customary percentage—generally 50 per cent.—taken off. To
facilitate future operations, and to enable the manufacturer to produce
different varieties of glue, the dry materials are sorted and stored in
different compartments of the store-shed.

Green waste, _i. e._, such as has not been limed must be taken in hand
at once, as otherwise it would taint the air, be attacked by rats and
other animals, and suffer injurious alterations by decomposition. The
manner of operation is as follows:

_Liming._ Prepare “milk of lime” by filling the pits, which are to
serve for the reception of the skin waste, with the required quantity
of water and dissolve in it 2 per cent. of calcium hydrate obtained by
slaking a good quality of quick lime. Stir thoroughly, and in order
that the water may become thoroughly saturated with the lime, let the
liquor stand for 8 or 10 days before placing the waste in it. The
liquor should stand about 9 inches deep over the waste in the pits.
The length of time the waste has to remain in the milk of lime varies
according to the material; calf skins requiring 15 to 20 days, sheep
skins 20 to 30 days, and heavy ox hides 30 to 40 days. The milk of lime
should be renewed once or twice a week, and thoroughly stirred.

For the purpose of liming, the quality of the lime used is of the
utmost importance, the milk of lime being frequently quite valueless
by reason of having become carbonated or a bad quality of quick lime
having been originally employed. It should be borne in mind that only
the hydrate of lime which is present in solution in lime water is of
use, whereas in milk of lime so much carbonate and other impurities
may be present that the liquid, though thick, may be quite useless.
The value of a lime should always be tested by determining the amount
of real calcium hydroxide, Ca(OH)_{2}, contained in it. The operation
according to S. Rideal, is conducted as follows: Water free from
carbonic acid is first prepared by boiling distilled water for half an
hour in a strong, round-bottomed Bohemian or Jena flask. While steam
is still issuing, the flask is removed for an instant, closed by a
well-fitting greased cork or a rubber stopper, and allowed to cool.
When the temperature has somewhat fallen, the cooling may be cautiously
accelerated by dipping into a pail of warm water, then transferring to
the cold stream from a tap. The water may be preserved in the flask
or, preferably, a number of bottles with vase-lined stoppers should be
filled quite full and retained for use.

From the sample of lime, well mixed, a small portion (about 0.25
gramme) should be accurately and rapidly weighed, placed in a
wide-mouthed, stoppered bottle holding about 300 cubic centimeters, 250
Cc. of the boiled water added, and then allowed to settle. The whole of
the calcium hydrate will now have dissolved. Fifty cubic centimeters
of the clear liquid should now be withdrawn by a pipette, transferred
to a flask, colored with an indicator—either phenol-phthalein,
methyl-orange, or litmus may be used—and its alkalinity determined by
running in decinormal hydrochloric or sulphuric acid from a burette
till the change of color occurs. Each cubic centimeter of the acid
corresponds to 0.0028 gramme of calcium oxide, or 0.0037 gramme of the
hydrate, Ca(OH)_{2}. The amount by calculation will give the percentage
of real lime present in the sample. It is well to notice that any soda
or potash present will equally neutralize the acid, and be returned
as lime, but as these are of almost equal efficiency their presence
in _small quantity_ has no disadvantage. For special work it will be
necessary to have a full analysis. As a rule the product made from
limestone, or “stone lime,” is the best article in commerce, and is
much more free from stones and clay than “gray lime” or “shell lime.”
The best stone lime contains sometimes only ½ per cent. of impurities,
and seldom more than 5 per cent., while inferior kinds of gray lime
may contain as much as 50 per cent., and would be of little use in
glue-making.

After removal from the lime pit, the material is placed in willow
baskets or nets, and immersed in the stream to remove the greater
portion of the lime, which is generally effected in a few days. It
is still more effectively accomplished by placing the waste, after
soaking in the willow baskets, in the wash drums. After taking it from
the baskets or wash drums it is spread in the drying yard to drain and
dry, the desiccation being accelerated by turning it over with a fork
several times a day. While drying, the quick-lime is converted into
carbonate, the latter exerting no disturbing effect in the manufacture
of glue. When sufficiently dried, the material is ready for boiling,
and the crude glue thus obtained can be stored for any length of time,
until wanted for further manipulation.

In summer it is scarcely possible to cleanse the raw material as
rapidly as it is brought to the factory, and to work it immediately
without putrefaction setting in, and for this reason it would
frequently be risky to purchase larger quantities of it, even if
offered at very favorable terms. During the colder season of the year,
drying of the cleansed raw material is such a slow operation, that
in order to prevent putrefaction, recourse would have to be had to
artificial heat.

These drawbacks can, however, be overcome by the use of carbolic
acid, which possesses in a high degree the property of preventing
putrefaction. It is quite cheap, and as but a comparatively small
quantity of it is required, the additional cost need scarcely be taken
into consideration, since the value of glue-stock annually destroyed by
putrefaction is considerably greater than the expense for carbolic acid.

The raw material is thoroughly cleansed, and while in a moist state
is gradually brought into a brick cistern or large vat, carbolic acid
solution being poured over each layer, so that, when the cistern or vat
is filled, it stands about an inch or two deep over the material. The
latter may be left in this state until wanted.

The carbolic acid solution is prepared by dissolving 2 lbs. of carbolic
acid in 1000 quarts of water; the fluid thus obtained possessing a
slight odor of smoke. The washed glue-stock treated as above described
with carbolic acid remains absolutely unchanged, and when wanted needs
only be taken from the cistern and worked like fresh material.

In plants having no running water at their disposal and depending
entirely on well water, and where the waste water has to be discharged
into rivers or creeks, water containing carbolic acid should be used
for all the washing operations, a fluid containing 1 to 2 parts of
carbolic acid in 10,000 parts of water being sufficient for this
purpose. Such an addition of carbolic acid prevents the wash-water from
becoming foul.

Carbolic acid has the tendency of hardening the glue-stock and
imparting its odor to the glue, and among other antiseptics,
formaldehyde and boric acid have been recommended for the purpose of
preventing putrefaction for a reasonable time. Formaldehyde in weak
solution (1 part in 10,000 to 100,000 parts water) has been found
beneficial. In this small quantity it does not harden the stock nor
affect the subsequent boiling, as it is dissipated by the heat. Boric
acid and its preparations, notwithstanding their low antiseptic power,
are much in favor. A fluid containing 1 part boric acid in 200 parts
water will have to be used.

The principal varieties of hides and leather for glue-stock may be
classed as follows:

1. Bullock leather from old animals, highly limed, mixed with rump
pieces, also with horse leather, the latter being thin, of a dark color
and soft, and is of less value than bullock leather, because it yields
a dark glue. Fat leather is bullock’s leather from fat, stall-fed
cattle, and before use has to be freed from fat (by means of benzine).

2. Pieces of hide from the lower parts of the limbs of cattle, not
limed and with the hair; they form excellent glue-stock, yielding a
very adhesive glue.

3. Worn-out hinges from weavers’ looms, consisting of strongest
untanned bullock’s hide. When treated with lime they yield a very
strong glue, but are worked with difficulty.

4. Whip leather. This is waste in the manufacture of whips, and
is derived from thick tawed bullock hide. It yields an excellent,
light-colored glue.

5. Calf leather. Broad, thin, translucent strips, slightly limed,
yields glue of a very light color.

6. Calves’ heads. The skin of calves’ heads, limed, without hair. They
constitute the best material for gelatine, and form a special article
of commerce.

7. Calves’ feet. The skin from the last but one leg-joint which is cut
off from dry, unlimed, haired skins. It is the best material next to
calves’ heads.

8. Knapsack leather. Old knapsacks of calf skin and waste in the
manufacture of new ones, tawed with the hair on with alum and common
salt. When suitably washed this yields good glue-stock. The alum and
common salt have to be completely removed by washing. The hair is no
detriment to the process of boiling, it serving as a filter for the
glue running off. To this class belong also all kinds of fur waste,
especially remnants of old fur coats (sheep skin coats), from which the
wool is removed and the skin used as glue-stock. All these materials
having been treated with alum and common salt have to be freed from
them by suitable manipulation.

9. Hare and rabbit skins freed from their fur. They yield a
light-colored glue of little consistency.

10. Cut rabbit skins. In depriving these skins of their fur, they are
cut by a machine into fine threads of even size. In France they are
worked into size for gilders’ use which is highly valued.

11. Sheep and lamb leather (goat leather) limed, thin and very light,
yields but a small quantity of glue of little consistency. To this
class belongs the waste in the manufacture of kid gloves. Waste of
morocco and other varieties of similar leather, pressed into bales and
secured with wire, comes into commerce under the name of Levant leather.

12. Waste obtained in paring kid leather and in the manufacture of
gloves. It constitutes a flocculent powder and yields very thin glue
liquor with slight adhesive power. Before boiling, the substances used
in tanning must be completely removed by washing.

13. Surrons. These are untanned, unlimed skins of various wild animals
(antelopes, gazelles) which have been used for packing leaf tobacco and
various drugs. They form good glue stock.

2. BONES AND CARTILAGES.

In addition to hides, bones are a material highly valued by the glue
boiler. Chemically speaking, the framework supporting the fleshy
tissues of the animal order, and which we call bones, is a combination
of phosphates of lime and magnesia, carbonate of lime, and alkaline
salts, united with fatty and cartilaginous matter. To the latter we
look for our yield of glue; to the fatty matter for the fat, and to the
phosphates for the basis of fertilizers.

Bone cartilage is composed of carbon, hydrogen, oxygen and nitrogen,
the percentage composition being practically constant, whether the
cartilage be from an old or a young animal. The bones of the young
are, however, much richer in cartilage than those of the old. This is
reversed in the case of the inorganic or mineral matter, the old having
the greatest yield of phosphates.

Then again, the fatty matters are more in evidence in full-grown
animals than in youth or age; also in the thigh and leg bones the
yield is higher than in the heads, ribs or shoulder blades, the latter
averaging 12 to 13 per cent., whilst the former runs 18 to 19 per
cent.[1]

[1] Bone Products and Manures. By Thomas Lambert. London, 1901.

Bones being less subject to putrefaction than skin-stock, they are
not brought into commerce in a prepared state. They are mainly bought
by contract from various dealers within easy access to the works. The
rates are generally fixed for a certain period, and cover all classes
of common bones, whether fresh butchers’ or a mixture with partly
boiled bones. Bones differ considerably in their value. A fresh bone
will yield the highest percentage of fat and glue. On the other hand,
partly boiled bones may contain only 6 per cent. fat with 30 per cent.
water. In buying bones the manufacturer should exercise great care, as
the dealer sometimes finds ways and means of including hoofs, horns,
iron, beefy matter, and even pieces of brick. Naturally they form
weight, but, excepting the horns, have no value.

To separate the different classes of bone coming into the works, and
arrange them according to the amounts they would produce of fat and
glue, is no doubt a desirable object, but in practice it is seldom
carried out. However, if the manufacturer wishes to undertake this
tedious work, it is recommended to make the following distinctions:

1. Bones of young animals, sheep, calves, dogs, cats, etc., being
readily disintegrated, are thrown into one pile, and also the light
bones of oxen, such as skull bones, shoulder bones, the vertebra of the
tail, etc.

2. A second pile is made of the foot bones of goats, sheep and cattle,
provided they can be had, as is the case in the United States and
England, in sufficiently large quantities.

3. Scraps and shavings from bucks’-horn from turners and button-makers.

4. Thick bones of oxen, horses, etc., which must remain longer in the
lime-bath, together with waste of hard bones from turners.

5. Where large quantities of bones are handled it is advisable to sort
out the bones of the upper thigh, as they can be more advantageously
used for the manufacture of piano-keys, handles for tooth-brushes, etc.
Hoofs, which are frequently found, should be thrown out, as they yield
no glue and can be utilized for other purposes.

The further manipulation of the bones for the manufacture of glue
requires first of all their crushing or grinding in a stamper or mill.
By this crushing or grinding of the bones two objects are attained,
namely, they are more readily deprived of their fat and present more
points of attack to the corrosive agents to be used later on. The
crushed bones are put in a large boiler, and for a few hours subjected
to the action of steam. Leg bones, as well as horns, should not be
boiled, as they contain no fat, and would lose too much glue-yielding
substance. After boiling, the bones are placed in a lime vat for 8 to
14 days. The water used for boiling the first portion of bones may be
used for a second one.

The extracted fat amounting to 4 or 5 per cent. of the quantity of
bones used, is taken off the surface of the cold liquor and the latter
may be utilized as a fertilizer, or fed to cattle.

For crushing the bones, a stamping mill is generally used, it yielding,
when properly constructed, material for the manufacture of glue, as
well as granulated bones which form an excellent product for the
preparation of animal charcoal.

Since animal charcoal in pieces of quite even size is now in
general demand, it is recommended to manipulate the bones in the
above-described manner, to sell the granules to the manufacturer of
animal charcoal, and use for boiling glue only the completely-crushed
portions and the porous bones which are not at all suitable for the
manufacture of animal charcoal.

[Illustration: FIG. 6.]

Fig. 6 shows a stamping mill very suitable for the crushing of bones,
the illustration showing the mill open on the left side and closed
on the right. It is furnished with 16 stamps, _D_, each stamp being
provided with a cast-iron shoe. The stamps are lifted by means of a cam
shaft in such a manner, that the height of fall of the outermost pairs
of stamps is least and that of those in the centre greatest. Between
the inner stamps is a sieve _H_ with meshes of sufficient size to allow
the largest pieces, which can be produced by granulation, to fall
through.

Underneath the sieve is an Archimedean screw _K_ for carrying off the
pieces of bone passing through the sieve.

[Illustration: FIG. 7.]

[Illustration: FIG. 8.]

The base of the stamping mill consists of iron plates so arranged
as to form steps, the plates lying towards the center of the mill
constituting the lowest steps. Every two stamps standing alongside one
another rest upon such a step. When the mill is set in motion, the
bones reaching the stamping trough from the right and left fall upon
the steps, and are crushed by the descending stamps.

As a rule, the bones to be stamped are not brought directly into the
stamping trough, but are first passed through a crushing mill and
the coarser pieces thus obtained are subjected to the action of the
stamping mill.

Figs. 7 and 8 show a well-constructed bone crusher. It consists
essentially of two cast-iron rollers _A_ and _B_, furnished with
case-hardened cutters. The bones are introduced through the hopper _B_,
and the rolls set in motion by means of cog-wheels _a_ and _b_. The
bearings of the roll _B_ run in a carriage which can be shifted by the
lever-construction _f i_. The object of this contrivance is to allow
of the roll _B_ giving way in case a harder material than bones, for
instance, a stone, passes between the rolls.

[Illustration: FIG. 9.]

The Crosskill bone mill, Fig. 9, as described by S. Rideal, is intended
to be driven by a strap from the fly wheel of a common portable
engine. It consists of a pair of strong rollers made of wrought-iron
with case-hardened cutters, and a revolving or oscillating riddle for
separation of the ground bones as they fall from the cutters; the whole
carried by a substantial cast-iron frame. The mill will grind from 6 to
16 hundred-weight per hour with a three to eight horse-power engine.

For sorting the crushed bones into pieces of equal size, a sieve, Fig.
10, is used consisting of a drum constructed of narrow boards covered
with wire-netting of different degrees of fineness. The upper portion
_A_ of the drum consists of narrow-meshed net and through this falls
the fine meal which is conveyed by the Archimedean screw _F_ over the
frame _F G H_ into vessels serving for its reception.

The lower section, _B_, of the drum is furnished with netting, the
meshes of which become gradually wider towards the lower end, and,
hence, the smallest particles of bone fall through the funnel, _D_, the
medium-sized ones through _E_, and the largest ones through _F_. Pieces
which cannot pass through _F_, leave the drum at _G_.

In factories manufacturing glue as well as animal charcoal, the larger
pieces are steamed by themselves to obtain their fat, and then charred,
while the small pieces and the meal are utilized for glue.

[Illustration: FIG. 10.]

The lime-bath used for bones should be of the same strength as that
for skin-stock. After removal from the lime vat and washing, the bones
are put in a tank of stone or wood (brick pits should not be used)
containing cold hydrochloric acid of 70° Bé. or 1.05 specific gravity
(= 10.6 per cent. HCl) for thick bones, or half that strength for thin
bones, and are thus left to digest for 8 to 14 days, being frequently
stirred and fresh acid added. By the action of the acid the calcium
phosphate is dissolved and the bones become cartilaginous, flexible
and transparent. The phosphates can be precipitated by ammonia, or
the whole evaporated with charcoal or silica, and distilled to make
phosphorus.

When sufficiently softened, the stock is washed in wicker baskets or a
washing drum to remove adhering acid. They are then placed for one day
in the lime liquor, again washed, and then either dried or stored away
for future use, or boiled at once to glue, while in a moist state.

Leg bones, horns, and other soft bones which contain scarcely any fatty
matter are not steamed for the reason previously stated, but in all
other respects are treated like steamed bones.

It is of the greatest importance that the bones should be thoroughly
freed from acid, since even the smallest quantity remaining behind
exerts an injurious effect upon the finished glue. It is therefore
recommended to test the water draining off, or the bones themselves,
with litmus. If the tincture turns red, it is a sure indication of the
presence of free acid, and the washing must be continued until the blue
color of the tincture remains constant.

Gerland’s suggestion, to use dilute sulphurous acid in place of
hydrochloric acid for dissolving the phosphates of the bones, and
to evaporate the sulphurous acid by heating, whereby the phosphates
are precipitated in an insoluble state, has now been quite generally
introduced.

For the preparation of gelatine from bones, Jullion and Pirie’s
process may be recommended. It requires a somewhat expensive plant,
but saves hydrochloric acid and time. The process consists essentially
in dissolving the phosphates of the bones in vacuum. A box of wood,
or better of granite, which can be closed air-tight, is required
for this purpose. The box is filled with bones, and acid of the
previously-mentioned strength poured over them. The box is then closed
and the air pumped out by water or steam power. The smallest cracks
and pores of the bones are thus freed from air, and the latter is
replaced by hydrochloric acid, which in this manner acts rapidly and is
completely exhausted. The remaining crude glue is then further worked
in the usual way.

Bones honey-combed by putrefaction, exposure to the weather, or burial
in the ground are of little or no value to the glue-boiler, as nearly
all the glue-yielding substance has been destroyed; they should
therefore be thrown out in buying stock. The ammonia which is formed
when putrefaction sets in, colors the glue dark.

3. LEATHER WASTE.

Leather tanned with a substance insoluble in water is not directly
suitable for manufacturing glue, but can be made so by a special
process, which, though somewhat tedious, nevertheless pays for the
trouble.

In using such stock the manufacturer should make a distinction
between old and new leather. The principal materials of this kind,
large quantities of which contribute their quota to the glue-boiler’s
stock, are old shoes, straps, harness, etc., and further, waste from
shoemakers, trunk-makers, and in fact from the shops of all workers in
leather except those using alumed leather.

Before boiling the leather waste to glue, the removal of all traces
of tannin becomes absolutely necessary, since the retention of the
smallest quantity prevents the animal tissue from dissolving in water.

The various methods proposed for the preparation of the leather waste
differ either in the chemical solvent used, or in the mechanical
manipulation of the waste.

The principal point in all methods is to comminute the waste as
uniformly as possible to facilitate the complete removal of the tannin.

Various machines, some very complicated, have been proposed for the
comminution of the waste, but a rag engine or “hollander” such as is
used by paper-makers deserves preference for the purpose, as it not
only comminutes, washes and prepares the waste in a suitable manner for
the manufacture of glue, but the leather pulp when mixed with rags or
woody fibre gives a substitute for leather which is very tough and of
good appearance, and can be worked into many articles.

After the preparation in the hollander and careful washing the waste is
treated, according to Stenhouse, under a pressure of two atmospheres in
a boiler with water to which is added 15 per cent. of the quantity of
waste to be treated at one time of slaked lime.

By another method the extraction of the tannin is effected by boiling
the leather pulp with caustic soda of 1.025 specific gravity for from
six to twelve hours. After drawing off the water and pressing out, the
pulp is again boiled with caustic soda of the same concentration. The
next process is to carefully wash out the soda, which is best effected
in the hollander.

By neutralizing the soda lye in the fluid drawn off after the first
boiling, it can be re-used for tanning or purposes for which tannin is
required.

According to another method, the _modus operandi_ is as follows:

Dissolve 1½ lbs. of oxalic acid in 3 gallons of water, pour the boiling
solution over 110 lbs. of waste, and keep the mixture in a water-bath
at a temperature of 176° to 212° F. This effects the solution of the
pulp. Then dilute the solution by adding gradually 4 gallons of water
until a uniform mass is formed. Now add 5 lbs. of lime slaked to a
thin paste, and mix the whole thoroughly. The mass becomes friable and
pulverulent. It is passed through a wire sieve and then exposed to the
air. In three to four weeks the tannin is entirely destroyed, which
is recognized by the mass assuming a lighter color. The lime is then
removed by washing with water and hydrochloric acid. If the tannin
has not been entirely destroyed by exposure to the air, add 1 lb. of
liquid ammonia and a like quantity of pyrolusite to every 110 lbs. of
leather substance when boiling it to glue. The oxygen yielded up by
the pyrolusite, which, in the presence of ammonia, exerts no injurious
effect upon the glue, destroys the last traces of tannin. Frequent
stirring with a shovel while the material is exposed to the air and
moderate heating, facilitates the destruction of the tannin.

4. RAW MATERIALS FOR FISH GLUE.

The air-bladders or sounds of various fishes contain much glue-yielding
substance and on account of its purity, the product known as isinglass
obtained from them is preferably used for culinary and medicinal
purposes. The high price of the raw material excludes it from being
used by the glue-boiler, but as he manufactures substitutes for
isinglass, and should therefore have a thorough knowledge of the
article with which he has to compete, its manufacture will be included
in this treatise. Since, however, the work of the manufacturer is
finished with the preparation of the raw material, _i. e._, of the
air-bladders into crude glue, isinglass and its substitutes will be
referred to later on.

There is a material difference between isinglass and glue manufactured
from entire fishes. The raw material is, of course, limited to certain
localities. The principal point to be observed in the manufacture of
fish-glue is the removal of the skin, which is effected by means of
dilute sulphuric acid.

After removal of the last traces of acid, the fatty matter of the
fishes is saponified by a treatment with milk of lime frequently
renewed. After washing out the lime, the pulpy mass is placed in a
solution of sodium hyposulphite, alum, and common salt, where it
remains for a few days. The liquor is then drawn off and replaced by
a mixture of solution of alum, dilute sulphuric acid and nitric acid.
After macerating in this mixture for a few days, the mass is thoroughly
washed and boiled to glue, and the resulting product clarified with
sulphurous acid or alum solution. As will be seen, the entire process
is tedious, requires many chemicals, and besides the yield of glue,
which has no specially good qualities, is small. It is used as a
substitute for isinglass for clarifying liquids. The best proof that
the business is of but little importance is found in the fact that
no fish-glue has been exhibited at any of the late international
exhibitions.

The scales of large fishes, such as carp, give more favorable results.
They are treated with hydrochloric acid in a similar manner to bones.
The scales do not dissolve entirely, a horny insoluble mass, giving
no glue, remaining behind after the solution of the glue-yielding
substance.

CHAPTER IV.

MANUFACTURE OF SKIN GLUE.

The thorough preparation of the raw materials will materially
facilitate all succeeding operations, which may be classified as
follows:

1. Boiling the glue.

2. Clarifying the glue-liquor.

3. Forming or moulding the glue.

4. Drying the glue.

However, before entering into the description of these operations, it
will be necessary to refer to an intermediate product, which has been
previously mentioned under the name of crude glue, and is prepared, for
instance, by tanners and manufacturers of parchment, but also forms in
some localities a special branch of industry.

This crude glue is actually not glue, but a glue-yielding substance in
such a state of preparation that it can be directly used for the first
operation, namely, boiling. It consists of waste of skins and leather
of all kinds, completely cleansed, dried and limed, and in the case
of leather treated with agents for the extraction of the substances
used in the tanning. As will be readily understood, the operations
required for the preparation of this stock are virtually the same as
those described in the previous chapter for raw materials and need not
further be here referred to.

The bulk of such stock is prepared by tawers and manufacturers of
parchment, though a considerable quantity of it is also derived from
waste in the manufacture of gloves. The product from the latter source
is also found in commerce under the French names _Colle franche_ or
_Brochette_. However, if such stock is used, it is best to again
immerse it in lime water, after which it should be thoroughly washed.

The manufacture of glue from hide and leather waste differs materially
in many respects from that of bone glue, it being the more simple
process, as no other preliminary operations than the preparation of the
glue-stock are required. The first operation is

1. COOKING OR BOILING.

For this operation any kind of boiler may be used, but the materials
should be supported on a perforated grid a little distance above the
bottom, so as to save them from risk of scorching. In the centre of
the grid stands a conical pipe 2 to 3¼ feet long, perforated like the
grid and communicating with the space between the grid and the bottom
of the boiler. The height of the boiler can be increased 1 to 1½ feet
by placing an annular piece upon the rim which is bent upwards for its
reception.

The size of the boiler depends on the quantity of raw material to be
worked at one time. It is best to choose boilers holding from 110 to
440 lbs. of glue-stock, and to place two, four or more of such boilers
in one hearth.

The manner of using such a boiler is very simple. Straw is placed upon
the false bottom in such a manner as to cover its entire surface, and
extend up the sides of the boiler at least as far as it is touched by
the flame. The object of the straw is to serve as a filter, and protect
the materials from injury by the flame. But for the production of
entirely pure gelatine or glue, straw cannot be used, as, by boiling,
it yields a yellow coloring matter, which passes into the glue. Barley
straw gives a less intense coloring matter than rye straw.

In case straw cannot be used, the material is placed in a large bag,
previously thoroughly boiled, and suspended in the boiler so as not to
touch the sides. By this means scorching is prevented even if the fire
touches the bottom as well as the sides of the boiler.

The boiler having been heaped with material so high as to overflow the
brim and fill the annular piece placed upon it, is filled with water
as far as touched by the fire. The fire may now be started. The hearth
in which the boiler is placed should, of course, be so constructed
that the gases are uniformly distributed and the water quickly brought
to the boiling-point. When the water commences to boil, bubbles of
steam ascend from the space beneath the grid and, passing through the
perforations of the conical pipe, penetrate the glue-stock. Thus the
first formation of glue takes place, and the stock begins to settle
down gradually as it goes into solution. The stock heaped up in the
annular piece also sinks down gradually, and being partly heated by the
hot vapors and thus prepared for solution, is finally submerged in the
boiling solution and becomes soon entirely dissolved.

Waste of hide and horn piths are completely dissolved in five to seven
hours. No more water should be used than is absolutely required for
cooking the entire quantity of stock, because too much water renders
the solution too thin and gives a jelly of little consistency and
difficult to dry. Concentrating the glue solution by continued boiling
is bad practice, as it is detrimental to the resulting product by
reason of the glutin undergoing a gradual transformation.

It is best to start with a slow fire to give the stock time to soften
and thus prepare it for solution. When somewhat softened, the mass is
brought to boiling and the latter kept up, gently and uniformly, until
solution is complete. Solution is promoted by careful stirring, but
care should be had not to disarrange the straw upon the grid and on the
sides of the boiler as this would interfere with proper filtration of
the glue solution.

The duration of cooking depends on the nature of the raw materials.
Scraps of skin from young animals, antlers, sheep trotters, etc.,
dissolve in three to four hours, while waste from ox and horse hides,
or bones from old animals, require six to eight hours.

The progress of the operation is readily ascertained by pouring a
small sample of the gelatinous fluid in half an eggshell, and setting
it aside for a few minutes to cool. If a clear and consistent jelly
be obtained, boiling has been carried on to a sufficient extent, and
the liquid is drawn off. Any undissolved glue-stock remaining upon the
straw filter can be boiled by itself, and the resulting gelatinous
liquor utilized in the next boiling.

It is evident that quick and uniform solution of the materials, which
enhances the quality of the glue, is promoted by comminuting the
glue-stock either by grinding, stamping, or mechanical means.

The succeeding clarification of the glue is much facilitated by
removing while boiling the scum, consisting of fat, coagulated albumen,
lime-soap, accidental admixtures, and other impurities. Before drawing
off the gelatinous liquor it is advisable to withdraw the fire and
allow the contents of the boiler to rest for fifteen minutes.

The residue remaining upon the straw filter consists of hair,
lime-soap, undissolved particles of hide and bones, lime, etc., and is
utilized, after repeated boiling, as fertilizer or for the manufacture
of gas.

The mode of glue boiling above described is the oldest and at present
is only in use in small establishments. Fig. 11 represents a convenient
apparatus for the purpose. It consists of three boilers upon as many
different levels. The lower boiler, _b_, serves for the settling and
clarification of the glue. It communicates with the second boiler, _a_,
which contains the material to be acted on, by means of a pipe provided
with a stopcock, and is sufficiently heated by a small fire to keep
the glue liquid without allowing it to reach ebullition. The upper
boiler, _c_, which is heated by the waste heat of the chimney, serves
as an economical reservoir for hot water. The end of the discharge-pipe
of the settling boiler is provided with a filter of woven wire. As
the sides and bottom of the second boiler are lined with straw, which
acts as a preliminary filter, the glue runs off quite clear from the
settling boiler.

When this mode of manufacture is adopted, two boilings can be made
per day, under favorable circumstances, so that, if the boiler has a
capacity of 220 lbs. of stock, which will yield from 110 to 132 lbs.
of dry glue, the daily fabrication will be about 220 lbs. of finished
product.

[Illustration: FIG. 11.]

In larger plants, the above described mode of extracting the glue-stock
with water has been superseded by the use of steam in a cylindrical
wrought-iron boiler, twice as high as wide, and capable of withstanding
a pressure of three atmospheres. The boiler is furnished with a
perforated false bottom underneath which terminates a steam pipe. It is
filled from above with previously softened glue-stock and the charging
hole hermetically closed. Steam is then gradually admitted and exerts
at once a dissolving influence upon the stock. A portion of the steam
condenses and forms with the dissolved glue-stock a concentrated jelly
which collects between the true and false bottoms.

For the escape of air a cock is provided which is closed as soon as
steam commences to escape from it.

[Illustration: FIG. 12.]

The advantages of this process are obvious. A larger quantity of
glue-stock can be extracted than in the boiler previously described,
and there is no danger of injury by scorching and consequent damage to
the color of the glue. More highly concentrated solutions are obtained
in a shorter time, and the spoiling of the glue solution by too long
continued cooking is prevented by drawing off the solution as quickly
as formed. The escaping hot vapors may be utilized for drying the glue,
softening the raw material, etc., the entire quantity of heat being
thus utilized. A further great advantage of this method is that there
is less annoyance from badly-smelling vapors than when boiling is done
over an open fire. A number of such boilers can be arranged in one
room and supplied from a common steam boiler.

Fig. 12 represents a boiler for extracting glue-stock with the use of
steam. It is provided with a lid, _D_, which is removed for charging
the boiler. The aperture, _E_, in front, serves for the removal of
the residue. Above the true bottom there is another false bottom,
perforated and movable, which can be covered with straw for preliminary
filtration. The steam reaches the glue-stock through a pipe which
passes through the actual and false bottoms, and is perforated above
the latter. The resulting jelly collects between the true and false
bottoms, where it is less exposed to the action of hot steam. The
escaping steam passes through the pipe, _F_, which is provided with a
stock-cock. The pressure in the boiler is indicated by the manometer,
_K_. After throwing the materials into the boiler they can be covered
with warm water, or, after the lid is closed, warm water is introduced
from a reservoir through a special pipe and distributed over the
material through a rose.

The boiler stands upon a frame sufficiently high to allow of
conveniently placing a vessel under the pipe _G_, through which the
jelly is discharged. The vessel, when full, is conveyed to the settling
vat, or the arrangement may be such that the jelly is directly run into
the settling vat.

In many large plants open jacketed pans heated by steam are still used
for treating the material. Fig. 13 shows an arrangement with two of
such pans; of course one, or a larger number may be used, according
to requirement. In the illustration the pan _I_ on the left is shown
in front view, and the pan _II_ on the right, in section. _K_{1}_ is
the actual pan enclosed by the jacket _K_. Steam circulates in the
space between pan and jacket, whereby the stock in the pan is heated.
_K_{1}_, in addition, is furnished with a steam coil _S_, which may,
however, be omitted.

The steam enters through the pipe _D_, the space between pan and
jacket, passes into the coil _S_, and escapes at _b_. The water formed
by the condensation of steam in the space between pan and jacket, as
well as that which runs off at _b_ from the coil _S_, is carried away
by the pipe _A_.

The pipe _L_ serves for conveying hot water to the pans, and the pipe
_F_ for the discharge of the finished glue liquor. The stirrer _R_, is
furnished with two paddles, and is set in motion by a transmission on
the ceiling of the room. It serves for keeping the stock in the pans
constantly agitated, solution being thus very much promoted.

[Illustration: FIG. 13.]

The mode of working with this apparatus is very simple. Water being
admitted into the pan through _L_, the glue-stock is introduced and the
mass brought to boiling by admitting steam. The finished glue-liquor
is from time to time drawn off through the pipe _F_ into the settling
vessel.

It is generally preferred not to concentrate the glue-liquor in the
pans to such a degree as required to obtain a jelly, which after
cooling, can be immediately moulded, experience having shown that less
concentrated liquors can be more readily and better clarified, and
yield a lighter and more transparent glue.

Mr. Thomas Lambert gives the following process of cooking: The skins
are taken to the glue-boiler, which is an open vessel, 8 feet in
diameter at the top and 7 feet deep, and provided with a perforated
false bottom, through the center of which passes a two-inch pipe, one
end dipping below a layer of water at the bottom, the other projecting
about half the height of the boiler, this part being covered with a
perforated hood to spray the liquor through the mass. The skins are
placed on the false bottom and the added water at the bottom of the
boiler is brought to the boil by means of a steam pipe. The steam not
being able to escape quickly through the dense mass of glue-stock
above, exerts a pressure on the water, forces it through the pipe, to
be sprayed through the mass, and ultimately works its way to the bottom
of the boiler to be forced up again. This continual circulation of the
hot liquor rapidly dissolves the gelatinous matter, and when a strength
of 18 per cent. dry glue is reached, the first run is made to the
evaporating pan, the liquor passing through a filter of fine shavings,
to remove any suspended matter. Fresh water is added to the boiler, and
the boiling renewed. Three extractions are usually made, the last being
used for size.

In order to avoid annoyance to the neighborhood from foul odors,
Terne’s glue-boiler shown in Fig. 14 may be recommended. The lead-lined
iron boiler _A_, with manholes _B_ and _C_, on top and side, is
furnished with a false perforated bottom upon which the glue-stock is
placed. Underneath the false bottom lies the coil _E_ with valve-box
_e_. The boiler is filled through the upper manhole with glue-stock and
water admitted, steam being at the same time introduced in the coil
and in order to quickly heat the water, direct steam is also admitted
to the boiler through the pipe _F_ and cock _G_. When the water is
boiling the cocks _G_ and _F_ are closed, the coil furnishing now
sufficient heat. During boiling some steam is allowed to escape through
the partly-opened cock _L_, all badly-smelling gases being thereby
carried to the fire-box of a boiler where they are burned. When boiling
is finished, the glue liquor remains for a short time in the boiler to
allow the melted fat to separate on the surface, the cocks _K_{1}_ and
_K_{5}_ and serving for drawing off the fat. The insoluble residues of
the glue-stock remain upon the false bottom and are taken out through
the manhole _C_.

[Illustration: FIG. 14.]

2. CLARIFYING THE GLUE-LIQUOR.

The clearness of glue, _i. e._, its freedom from undissolved
substances, is by no means a criterion of its value as an agglutinant,
since pulverulent inorganic substances (white lead) are frequently
intentionally introduced into some varieties, for instance into
Russian glue, without injury to their adhesive power. But as a turbid
appearance may also be an indication of unsoundness and decomposition,
the manufacturer endeavors by all means to obtain a clear product.

A strict distinction should be made between clearness and color.
Very dark-colored glue may be very clear, and a very pale variety
the reverse, yet both possess excellent qualities. Both properties,
clearness and light color, cannot be obtained by the same process.

Clearness will be first referred to. If the glue-stock has been
properly prepared by rendering adhering particles of blood and fat
innoxious by liming and subsequent careful washing, the separation of
the few remaining impurities, which may have passed through the straw
filter, is readily effected by allowing the liquor to stand, care
being had to keep it liquid as long as possible to give the grease
time to rise and the flocculent and fibrous impurities to settle. This
is best effected in a wooden vat surrounded by a wooden or sheet-iron
jacket, the intermediate space between jacket and vat being filled
with a non-conductor of heat, or, if required, it may be heated by the
introduction of steam. The grease is skimmed off as it rises, and when
the solid particles have settled the liquor is drawn off through a pipe
placed a short distance above the bottom of the vat.

The size of the clarifying vat depends on the size of the boiler.
It is, however, best to have two vats for each boiler, in order to
keep the first liquor, which is always clearer and more concentrated,
separate from the last run. To be able to draw the upper layers of
purer liquor into cooling boxes by themselves, the vats are provided
with faucets at different heights.

To prevent putrefaction of the liquor which readily sets in during
settling at a higher temperature, the vats should be kept scrupulously
clean, and from time to time rinsed with clean, hot water. It is also
advisable to line them with sheet-iron.

Should the above-described mechanical separation not prove sufficient,
recourse must be had to other means. Alum and sulphate of alumina have
long been used for clarifying, 1 lb. of either of them, pulverized,
added to every 300 gallons of liquor, being as a rule sufficient.
Either of these chemicals removes the albuminous and extractive
constituents of the solution, and converts the dissolved free lime into
sulphate of lime, which settles readily, and prevents putrefaction of
the glue solution while drying under unfavorable circumstances. The
quantity of alum mentioned above does not impair the quality of the
glue.

Albumen is sometimes used for the better qualities of glue, and
generally for gelatine, but a cheaper substitute is fresh blood, which
contains albumen and fibrin. Dry albumen is dissolved in cold water,
or white of egg is used direct, if procurable. Before adding either of
these substances, the liquor is cooled to 130° F., and the clarifier
well stirred in; then the temperature is raised to about 200° F., when
coagulation occurs, and the precipitate entangles the impurities and
falls to the bottom, requiring, however, from twelve to twenty-four
hours to clear. It is said that glues clarified with albumen have a
characteristic soapy smell and show a tendency to foam.

The precipitation of the lime might be better effected by oxalic acid,
and the organic substances removed as scum by adding to the boiling
mass some astringent matter, such as a decoction of oak bark or hops;
but the purification has, in either case, to be done at the expense of
glutin.

A glue liquor, which does not clarify by these means, is not sound, and
is derived either from spoiled raw materials, or such as have not been
thoroughly prepared, or has been injured in boiling.

A far more difficult matter than the removal of mechanical admixtures
is to free the liquor from the coloring substances from which
it derives its color, and to discolor it without injury to the
characteristic qualities of the glue.

The use of animal charcoal for such large quantities of somewhat
thickly-fluid solutions, which are liable to spoil at the high
temperature at which they would have to be filtered, is very
difficult, and the result not favorable, except the solutions could be
successfully deprived of their tendency to putrefy. The use of carbolic
acid is also in this case the only means of removing the great tendency
of the liquor to putrefy, and hence, if the liquor is to be discolored
by treatment with animal charcoal, it can only be done without danger
to the glue, by mixing it with carbolic acid.

The object is more easily effected by bleaching the raw materials
previous to boiling them to glue.

This is accomplished by placing the glue-stock, thoroughly limed and
while still moist, in a bath of chloride of lime, not too strong, as
otherwise the solution of the materials becomes difficult. A bath of
the proper concentration is made by dissolving about 9 ozs. of chloride
of lime in sufficient water to cover 110 lbs. of glue-stock. After one
hour add sufficient hydrochloric acid to obtain an acid reaction, which
is recognized by litmus-paper dipped in the bath turning red.

Although the glue-stock is not bleached entirely through by this
process, the thin portions and outsides of the thick material acquire
a lighter color, and the first run of glue solution will have a light
color and can then be treated further without much difficulty.

Sulphurous acid has been successfully used for the production of
colorless glue without the necessity of boiling.

Waste of hides and skins is the only available material for this
process. Place the waste in water until putrefaction sets in. When this
is the case wash the material in a bag or wicker basket in running
water. Then pour 2½ parts of sulphurous acid over 12 parts of wet
material, mix the whole thoroughly and let it stand in a hermetically
closed vessel for 24 hours. Now draw off the acid, and after washing
the material thoroughly repeat the operation. When the vessel
containing the mixture of material and sulphurous acid is opened for
the second time the foul odor should be entirely superseded by that of
sulphurous acid, this being a sure indication of the correct execution
of the process. Wash the material, and, after squeezing, throw it
into a vat large enough not to be filled by it more than two-thirds
full. After filling the vat with water allow the mass to digest at a
temperature of 109.4° F. for 24 hours. The result will be a gelatinous
solution, which is drawn off and converted into glue. The undissolved
residue is transformed into gelatinous solution by pouring water over
it and allowing it to stand at a somewhat higher temperature.

For carrying out this process and that of bleaching with chloride
of lime it is best to use a vat provided with a stirring apparatus,
somewhat like a hollander used by pape-rmakers, as being most suitable
for washing, disintegrating and mixing the material.

Glue-liquor may also be successfully bleached with sulphurous acid, and
in speaking later on of the manufacture of bone glue, a very practical
apparatus for this purpose will be described.

Glue-liquor bleached by sulphurous acid clarifies very readily and
is protected from spoiling. The resulting glue remains, however,
quite acid, and cannot be used for all purposes, especially not in
combination with colors, chemicals, etc., upon which the acid has a
destructive effect.

3. FORMING OR MOULDING THE GLUE.

After clarifying, the liquor is run into moulds of deal wood or sheet
iron, lightly joined and of a rectangular form, slightly converging
towards the bottom so as to allow the more ready detachment of their
contents. They are about 3.25 feet long, 10 inches wide at the top, and
7¾ inches at the bottom, and 5 inches deep. When very regular cakes of
glue are desired, cross grooves of the required shape are cut in the
bottoms. After being well cleansed and ranged upon a level the boxes
are filled to the brim through large funnels with strainer cloths
affixed to their barrels. It is best to place them upon perfectly clean
stone flagging slightly inclined towards a reservoir for the reception
of such portions of their contents as may run over. The apartment in
which the work is performed should be clean and airy, a dry cellar
being the best for the purpose. In place of a large number of boxes, a
shallow vessel lined with sheet-iron and capable of holding the entire
quantity of liquor is sometimes used, from which the solid jelly is cut
out in cubic masses, which are further divided.

This arrangement can only be recommended for establishments where
but one variety of glue is produced, and the different layers in the
clarifying vat are not separated according to their clearness. Before
running the liquor into the boxes the latter should be moistened with
water, or, if made of wood, coated with oil, stearine, or paraffin to
prevent the liquor from penetrating the wood and the solidifying glue
from adhering to the sides.

After the solidification of the glue, which generally takes place in
twelve to eighteen hours, the boxes are inverted upon a table with a
smooth top of wood or stone previously wetted, so as to prevent the
adherence of the gelatinous cake to its surface. To detach it from the
sides of the boxes the moistened blade of a large knife is generally
used.

Cutting the cubes of glue into commercial cakes or sheets is readily
accomplished by observing the following instructions:—

The shape of the cakes depends principally on custom. The consumer is
used to a certain variety of glue, and if it is not offered to him in
the customary shape, he might refuse it and take his custom elsewhere.
The quality of the glue is the next point to be considered. If very
dark, it is advisable to cut the glue into thin cakes, and if turbid,
into thick ones, in order to make this defect the less apparent.
Thicker cakes can also be cut if the conditions for drying them are
favorable, and thinner ones if the reverse is the case.

The mass is first divided by a steel or brass wire stretched over a
frame, like a bow saw, into horizontal layers. The size of these layers
is regulated by guides which are placed at distances corresponding with
the desired thickness of the cake of glue. Instead of one wire, as many
as the cakes of glue to be cut, can be stretched over the frame, which
is best made of iron and provided with conical pins by means of which
the wires can be tightened, in the same manner as piano strings, when
they have become slack by use.

The width and thickness of the cakes of glue are regulated by the
distance of the wires from each other, and the length by the width of
the box. The cakes thus formed are dexterously lifted from the block
with the moist blade of a large knife and placed upon nets.

Instead of using wooden or sheet-iron cooling-boxes, it is recommended
to pour a layer of liquor of the desired thickness of the glue cakes
upon large polished stone slabs, and when congealed, cut it into
sheets, which are placed upon the nets to dry. The advantages of this
method are obvious. The liquor cools more quickly by being exposed in a
thin layer upon a large surface, which reduces the danger of spoiling,
and a strong evaporation of water and consequent concentration take
place. Besides, the cakes show the smooth surface of the polished
stone, and become in a short time so hard, that when placed upon the
nets, the twine will make no impression upon them.

Liquors which in gelatinizing do not become very solid, are not run
into forming boxes, but upon glass or zinc plates, and thus spread out
in a thin layer, acquire sufficient solidity to be removed cake by cake
after being cut. The plates upon which the glue is run are placed in
frames and laid upon a table furnished with a rim about 1 inch deep.
To accelerate gelatinization of the liquor, the table is flooded with
water before placing the plates upon it.

Where cooling-boxes are used, the jelly when completely congealed is
placed upon a table with a stone plate, by inverting the boxes, and
then cut into cakes. Figs. 15 and 16 represent the tools for cutting
the jelly into cakes. The block of glue is laid upon the surface _A_,
Fig. 15, and the frame, _B_, is gently drawn along in the grooves, _a_.
In the upright portion of the frame are fixed wires at such a distance
from each other as required for the thickness of the cakes to be cut.

[Illustration: FIG. 15.]

[Illustration: FIG. 16.]

When the block of glue has been cut in this direction, it is divided
by cuts perpendicular to the former, into cakes of a size in which the
finished product is to be brought into commerce. The apparatus shown in
Fig. 16 serves for this purpose. The vertical bars, _a_, furnished with
the wire, _b b_, serve as guides. The sheets thus formed are lifted
from the block with the moist blade of a large knife, and laid upon
nets.

The machine shown in Figs. 17 and 18 is the invention of Mr. J.
Schneible, and it is for slicing and spreading glue-jelly preparatory
to drying, and it consists in the combination of a reciprocating cutter
with the jelly-box and a traveling belt-carrying frame for receiving
the slices as cut by the knife.

Fig. 17 is a partly sectional side view of the machine, and Fig. 18 is
a cross-section of the same.

[Illustration: FIG. 17.]

_A A_ are side bars of the supporting frame, fitted at the ends with
cross-shafts, _a´_, carrying pulleys, _a a_, around which are endless
belts, _b b_. _c c_ are slide-ways upon the bars, _A_, and _d d_ are
slides carrying a cross-plate, _e_, and also a plate, _f_, to which
plate _e_ is attached a knife or cutter, _g_, the cutting edge of which
is at the edge of the plate, _f_, and about the same thickness as the
slices to be cut. The cross-shaft, _h_, is fitted in boxes on bars,
_A_, and near one end thereof it is provided with cranks at its ends,
which connect by rods, _i_, to the slides, _d_.

[Illustration: FIG. 18.]

From the opposite ends of the slides, rods, _k_, pass to loose arms,
_l_, on the shaft at the opposite end of the machine, and the arms,
_l_, carry pawls, _l´_, that engage ratchet-wheels, _m_, fixed on
the shaft, so that the shaft, _h_, being revolved, the slides, with
plates, _e f_, are reciprocated, and at the backward movement of the
cutter the pawls engage the ratchet-wheels, and belts, _b_, are moved a
distance equal to the movement of the knife.

The jelly-box, _n_, is fixed to side bars, _A_, by brackets at its
ends, as shown in Fig. 18, and is placed above the cutter and the
plate, _e_, so that when the plate, _f_, is drawn out from beneath the
box the plate, _e_, takes its place for holding up the block of jelly.

In operation the block of jelly is placed in box _n_, resting on plate
_e_. A frame provided with netting—such as is used for drying glue—is
placed on belts, _b_, beneath the box, and the shaft, _h_, being
rotated by power, the cutter moves forward and cuts a slice from the
jelly. The plate, _f_, at the same time moving away, the slice passes
upon the frame, and the return movement taking place, plate _f_ is
carried beneath the jelly-block, and the belts being at the same time
moved, the frame is carried forward in position for receiving the next
slice apart from the first one. In this manner, as slice after slice
is cut, they are spread on the frame, and the frames, when filled,
are carried to the end of the machine for removal. The plate, _f_, is
adjustable, so as to vary the thickness of the slices cut.

The box may be divided into cells of any size desired, so that each
movement of the knife will cut a slice from the bottom of each cell,
and the box extending the full width of the drying frames, all the
slices cut at once will be properly spread.

In order to keep the plates, _e f_, moist, so as to prevent the
glue-jelly from sticking thereto, there are fitted at the sides of the
jelly-box, _n_, open-bottomed boxes, _o_, containing fibrous material
soaked with water, which, resting on plates, _e f_, keeps their
surfaces moist.

The machine saves the troublesome and expensive work of spreading the
jelly by hand, as has been heretofore practiced.

The knife is to be attached to plate, _e_, in any suitable manner, and
the surface of plate, _f_, may be corrugated, so as to slide on the
jelly more readily.

[Illustration: FIG. 19.]

The cutting apparatus patented by M. Devoulx, of Marseilles, is much
used in France. The machine stands upon a board or table, upon which
are fastened two uprights, far enough apart to allow of the passage of
a truck carrying the glue, which is cut into cakes by blades or wires
stretched between the uprights.

[Illustration: FIG. 20.]

Fig. 19 shows the perspective elevation of the machine with its truck.
The upper part is filled up for the reception of the glue to be cut up
into cakes. The sides are omitted in this figure in order to admit of
a better explanation of the separate parts.

Fig. 20 gives the same view, except that the truck, the upper part of
which is closed, is between the uprights, and contains the glue to be
cut.

Fig. 21 represents the moment the wires have passed through the glue
and cut it into cakes. In all the figures, _a_ is the wooden frame upon
which the machine rests, _b_ the table-plate fastened to the frame,
_c_ and _d_ are the uprights, between which the cutting wires are
stretched, and _f_ the truck carrying the glue.

[Illustration: FIG. 21.]

[Illustration: FIG. 22.]

Figs. 22 and 23 show the truck by itself, _g_ representing the bottom,
and _h_ the back, which is provided with slight grooves, into which
the wires catch to assure the entire cutting through of the block of
jelly; _i_ is the upper part of the truck, which opens by means of a
hinge, and when closed is fastened with the pin, _k_. This upper part
of the truck is fastened to the back part of the truck by means of a
screw, which allows it to be set higher or lower, according to the size
of the block of jelly to be cut; _m_ is the bar of a rack fastened to
the truck, and serves for moving the latter. The driving gear, _n_, the
shaft of which carries a crank, _o_, catches into the rack.

[Illustration: FIG. 23.]

Two boards, one on each side of the truck, serve to keep the block of
jelly in position, and guide the truck.

With this machine 120,000 to 130,000 cakes can be cut in five or six
hours.

3. DRYING THE CAKES OF GLUE.

Drying the cakes is without doubt the most precarious part of the
manufacture. The jelly contains a large quantity of water which, to
prevent decomposition of the jelly before it is converted into glue,
must be evaporated as quickly as possible. In favorable weather, drying
may be accomplished either in the open air or in covered sheds.

Drying in the open air is connected with many inconveniences, for if
the sun strikes the cakes of jelly when they still contain a large
quantity of water, they may become soft so as to run through the
meshes of the net, or they may dry so quickly as to prevent them from
contracting to their proper size without numerous cracks and fissures.
If frost supervenes, numerous cracks may be formed in the cakes from
the congelation of their water, or a shower of rain may cause much work
and damage. In consideration of all these inconveniences, it is best to
conduct the operation in a drying-room.

To insure a constant circulation of air, which is absolutely necessary
for the expulsion of the aqueous vapor caused by the evaporation of
such a large quantity of water, the drying-room should be at least 10
feet high, even if intended for summer use only, and the windows be
provided with Venetian blinds so as to shut out the sun, if necessary,
without disturbing the circulation of air.

To dry the cakes in heated rooms in winter is a more difficult matter,
as provision has to be made for the removal of the aqueous vapor, and
a current of warm dry air has to be kept up at the same time. But such
a room is an absolute necessity for the manufacturer on a large scale,
who, in order to carry on his business without interruption throughout
the entire year, must be independent of the changes of wind and weather.

[Illustration: FIG. 24.]

The size of the drying-room should be proportional to the daily
production. Constructions are fitted up with the requisite frames for
the reception of the glue cakes, and are heated by steam pipes arranged
along the walls. In the floor in the immediate neighborhood of the
steam pipes are openings, which can be opened and shut at pleasure,
for the admission of fresh dry air. The latter on entering the room
is heated, and after passing over the frames and absorbing water from
the glue cakes, escapes through openings in the ceiling to a space
above it from which it is withdrawn by means of ventilators in the
roof. A constant change of air must be kept up. The quick drying of
the glue is of the utmost importance, as otherwise the jelly putrefies
either entirely or partially, and the glue acquires a turbid and mean
appearance. Too much heat causes the cakes to bend and crack. The
cakes are laid upon widemeshed nets of twine stretched in frames 6½
to 8 feet long and 3¼ feet wide. Fig. 24 represents the form of nets
commonly used. The nets are placed upon frames, such as shown in Fig.
25, arranged around the drying-room in the neighborhood of the steam
pipes and air flues. As the cakes have to be occasionally turned upside
down upon the nets, the latter must be placed at convenient distances,
one above the other in the frames.

[Illustration: FIG. 25.]

The use of twine netting has been found to be attended with many
disadvantages, the principal ones of which are given by S. Rideal as
follows:

1. “Being freely handled in the making, the netting is almost always
impregnated with dangerous organisms which penetrate the moist glue
cakes, and cause moulding or putrefaction. When this occurs, it is
usually attributed to a state of the atmosphere, but if the cakes are
examined, the alteration will generally be found to originate along
the lines made by the netting. The fault could be cured by sterilizing
the net for an hour at 212° to 248° F. in a hot oven, but besides the
expense, the fibre is thereby weakened. Moreover, the spores of a few
bacteria, such as _Bacillus subtilis_, which is widely distributed and
has the power of liquefying gelatine, will bear a heat of 248° F. for
over an hour, and still be capable of growing.

2. “However smooth the fibre, the glue will stick in places, leaving
small remains, which being hygroscopic, become ’sour,’ and set up the
objectionable bacterial changes in the subsequent batches.

3. “Owing to sagging, rotting, scouring, or wearing into holes, the
life of cotton or hemp netting is so short that the constant renewal is
a considerable item. A whole batch is frequently spoilt by the fault
of a net. In some works, heaps of old netting are found, which become
very putrid in the rain and sun, and give rise to mysterious bacterial
inroads in the factory. In others they are regularly burnt under the
boilers.

4. “The considerable overlap or selvedge required for securing the
edges of the net involves a waste of the area, and also some difficulty
in refixing.”

For this reason metallic netting has been largely adopted. The best
material has proved to be a heavily galvanized iron-wire netting having
no less than 15 to 25 per cent. of its weight of zinc. It can be
strengthened by longitudinal and transverse wires or ribs. It must be
examined by the microscope to see that it is perfectly free from holes
or cracks, and should last at least two years in constant use.

The temperature of the drying-room requires careful regulation, and
should never be allowed to rise above 68° to 77° F., as otherwise the
glue would soften and run through the meshes of the net, or adhere so
firmly to the twine as to require the nets to be put in hot water for
its separation. Dryness of air is of far greater importance in the
drying process than a high temperature. To promote this dryness of air
and prevent the aqueous vapor from condensing, evaporating, and again
condensing upon the cold walls of the room, they are wainscoted. Thus
protected by a bad conductor, they acquire a higher temperature, and
the aqueous vapor, instead of being precipitated upon them, is carried
off by the air-currents.

As the cakes placed in the immediate neighborhood of the steam pipes
and near the floor where the dry air enters, dry quickest, the nets
containing them are shifted after some time to a higher part of the
drying-room and their former places filled with cakes still wet. When
the cakes are dry, they are finally desiccated in a room at a higher
temperature, which serves to harden and improve them.

In modern times drying-rooms have been almost entirely abandoned and
in this country long drying galleries are used, sometimes 250 feet
in length and 6 to 8 feet square, with traveling platforms on rails
carrying the sheets of glue on stout galvanized netting. Wood is found
to be a better material for the galleries than stone or brick.

Figs. 26 to 28 show an apparatus for drying glue which is the invention
of W. A. Hoeveller.

Fig. 26 is a plan section, and Fig. 27 a side elevation in section, of
this improved drying-alley. Fig. 28 is an end view in section.

The form and arrangement are as follows:—

_A B_ represent the two parts of the alley, separated by the partition
_C_, which is shorter than the alley, so as to leave a communicating
space at both ends.

At the front of section _A_, is located a blower, _D_, actuated by a
steam-engine or other motor, _E_, also located within the walls of the
alley. The whole current from blower _D_, is directed through section
_A_ of the alley, whence it turns into section _B_, and comes back
through it, to be again drawn into and forced out of the blower into
section _A_. By this means the contained air of the alley is set in
continuous motion through the two sections successively, and as the
structure is made as air-tight as practicable in such cases, the air
remains unchanged until the doors _F_, or either of them, are opened to
discharge the vitiated air and let in the fresh.

In sections _A_ and _B_, is placed the railway _a a_, to admit of the
convenient movement of the contents in process of drying, which are
generally set on cars or buggies.

[Illustration: FIG. 26.]

[Illustration: FIG. 27.]

[Illustration: FIG. 28.]

In section _A_, in front of blower _D_, is placed a steam or other
heating device, _G_, which may be of any form or design adapted to
allow the air from blower _D_ to pass through it and to heat such air
while passing therethrough. The inventor prefers the radiating coil
for such purpose, the steam entering at _b_, and emerging at _c_. At
the other end of the alley, which by the double construction is in
section _B_, just back of the blower and heating-coil, there is placed
a condensing-coil, _H_, of a construction similar to coil _G_, and
having inlet _d_, and outlet _e_. Through this condenser there is kept
flowing a refrigerating liquid or brine, which renders the condenser
very cold. The continuous current of air from the blower passes over
the contents of the cars or trays in the alley and takes up moisture in
its passage. After such passage the air is charged with moisture and
comes in contact with the coils of the condenser _H_, upon which the
charge of moisture is condensed, and the air emerges dry again, enters
the blower, and is again made the vehicle by which the moisture of the
glue or other contents is transported to and deposited on the condenser.

In drying glue by this method do not use the steam-coil at the first
stage of drying a charge, as the drying should not be effected too
rapidly; but as soon as the product begins to stiffen properly, admit
the steam to the coil _G_, and thereafter the operation is continuous,
as above described.

By doubling up the alley into two sections, as shown, the inventor is
enabled to erect the alley in a more contracted space. In a length of
ninety feet he obtains the benefit of a single alley one hundred and
eighty feet long. Section _B_ may, if desired, be located on top of
section _A_. Doors may be located wherever desired, to facilitate the
movement of the trays or cars and the placing of them in and their
removal from the alley.

[Illustration: FIG. 29.]

By the above apparatus the drying can be perfected in a very much
shorter time than can be done by the old alleys, and operations can be
conducted in hot weather without hindrance from the condition of the
atmosphere.

In cases where the atmosphere is dry enough to dispense with the
heater and the condenser, the inventor can throw the doors _F_ wide
open, extend the partition _C_ out to that end of the alley, and then
preserve a continuous forced draft of sufficiently dry air in both
alleys for the purpose. As there are many days during the year fine
enough to give reasonably dry air, operations can be conducted with
the blower alone in this way, and thus economize the steam and the
refrigerating-brine.

[Illustration: FIG. 30.]

Figs. 29 and 30 show a longitudinal section, with upper and ground
floor plans of a modern drying-house, as given by Thomas Lambert. In
the ground floor the whole of the liquors are jellied in coolers,
and then cut into cakes by the two cutting machines in the centre.
Here a hoist, _E_, Fig. 30, is placed which carries the cut cakes on
“glasses” to the floor above. This forms the drying-floor, and is
partitioned off in three divisions, running nearly the length of the
building. The two outer divisions form the tunnels proper, and at the
ends are fixed two powerful revolving fans, driven at high speed and
drawing the air through the tunnels at a high rate. At the opposite
ends of the fans are fixed a series of 6-inch pipes, heated up by
waste steam, and the air passing between is warmed up to any desired
temperature, of necessity below 78° F. In the center passage a number
of girls are employed in transferring the cut cakes to the nets, which
are built upon a carriage running on a small railway. The carriage
with the complement of filled nets is run to the end of the division,
transferred to the lower railway, _C_, by which it is carried either
to the right or left hand tunnels as desired; the glue when dried on
the nets is run to the other end and by another lower railway brought
to the middle division, and ultimately by the hoist raised to a large
store-room, seen in section, where the glue is sorted and bagged. At
the end of the store-room is placed a grinding machine, and all the
off-color and twisted cakes are ground to a powder and sold as powdered
glue. The manufacturer by varying the size of the cake, its thickness,
and its color, may make any number of grades from the same boiling.

Fleck proposes to accelerate the drying of glue by utilizing the
water-absorbing power of some salts, such as Epsom and Glauber’s salts,
ammonium sulphate, crystallized acid sodium sulphate, etc., for the
purpose of withdrawing water from the glue cakes. For the practical
application of this principal a shallow, water-tight, wooden box is
required. The bottom of the box is sprinkled with a layer of the
water-absorbing salt about half an inch deep, and covered with a moist
linen cloth. Upon this is placed the jelly cut into sheets and also
covered with a moist cloth, a layer of salt being finally scattered
over it. After standing for a few hours, the box is slightly inclined
and the salt solution allowed to drain off through a hole in the
bottom, the dropping ceasing in from 12 to 18 hours. If now the upper
cloth is taken off with its layer of salt, the glue beneath it will be
found so far deprived of its moisture that when placed in the sun or
exposed to other heat, it will become completely dry in a short time
without either melting or spoiling, and in winter may be laid upon
drying-floors with the same result. The salt-solution formed may be
evaporated to crystallization and the salt thus obtained be again used.

After the treatment with the salt, the jelly contains 70 to 75 per
cent. of anhydrous glue, while the content in jelly not thus treated
varies between 7 and 28 per cent. according to the concentration of the
liquor from which it has been derived. It is claimed that the adhesive
power of the glue is not injured by this treatment.

Commercial glue must not only be thoroughly dry, but should also
present a good appearance, showing especially lustre. However, after
drying, the glue is dull, spotted, dusty and sometimes even mouldy. To
give a good lustrous appearance the dry cakes are dipped in warm water
and replaced upon the nets to dry.

CHAPTER V.

MANUFACTURE OF BONE-GLUE.

The manufacture of bone-glue differs chiefly from that of skin-glue in
the processes employed for the conversion of the glue-yielding tissues.
This conversion may be effected by boiling the bones with water, or
subjecting them to the action of steam, or by first extracting their
mineral constituents with acid, and boiling the remaining cartilaginous
mass with water until dissolved.

When the finest quality of all varieties of glue, namely, colorless
gelatine, is to be manufactured, the bones should not be comminuted in
a stamping mill, because in consequence of the unavoidable development
of heat, they acquire a slightly empyreumatic odor which adheres to the
gelatine prepared from them, and cannot be removed.

In factories working on a small scale, the bones are comminuted by
hand, being placed upon a grate-like support of heavy iron rods
and crushed with a wooden hammer, the face of which is studded
with big-headed nails. In larger establishments the crushing rolls
previously described are used, and in order to lessen the effect of
heating as much as possible, the crushed bones are allowed to fall
directly into a vessel filled with water.

Fat being a very valuable constituent of bones, it should be gained
as completely as possible, by boiling or steaming the bones, or by
extracting them by means of a solvent, such as benzine or carbon
disulphide.

1. BOILING BONES.

This is the older and more incomplete process of extracting the fat.
The bones are placed in a boiler, covered with water so that it
stands a few inches deep over them, and the whole is boiled over an
open fire. The melted fat collecting on the surface of the water is
skimmed off. By boiling, a portion of the glue-yielding substance is,
of course, converted into glue, and passes into the water. In order not
to lose this glue, the same water is repeatedly used for boiling fresh
quantities of bones, and is finally used for feeding pigs. By this
method 4 to 5 per cent. of fat is at the utmost obtained.

The bone fat obtained by direct boiling of the bones, is, if entirely
fresh material has not been used, of very inferior quality. It is dark
yellow to deep brown and of a disagreeable odor. It is only fit for
certain purposes, and to be utilized in the manufacture of soap has to
undergo a special process of purification, whereby it is rendered white
and odorless.

2. STEAMING BONES.

In order to obtain a larger quantity of fat than is possible by
boiling, the bones are preferably steamed, _i. e._, subjected to the
action of high-pressure steam. This is effected in a closed cylinder
of thick boiler-plate, into which steam of ½ to 1 atmosphere pressure
is admitted. The cylinder is provided with a perforated false bottom
upon which the bones are placed. By steaming for two or three hours,
all the fat is extracted from the bones and collects, together with
the condensed water formed by the steam coming in contact with the
cold bones, underneath the false bottom. However, by the continued
action of high-pressure steam upon the bones, a considerable portion
of the glue-yielding tissue is converted into glue, which passes into
the resulting liquor. This, however, is no drawback if only fat and
glue are to be obtained from the bones, since by continued steaming, a
liquor still richer in glue results, and need only be evaporated. But,
as a rule, the greater portion of the bones, especially the granulated
parts, are to be utilized in the manufacture of animal charcoal, and,
hence, great care has to be observed in steaming.

Animal charcoal is produced by calcining bones in vessels from which
the air is excluded, whereby the glue-yielding tissue is converted
into carbon, which is distributed upon the bone-earth. Since the value
of animal charcoal depends on the quantity of carbon it contains, a
product prepared from bones highly steamed, will evidently be of little
value, as a considerable portion of the glue-yielding substance has
been converted into glue.

If the bones are to be used for the production of animal charcoal they
should be subjected to the action of high-pressure steam only long
enough to extract the fat, but the resulting glue-liquor is very thin
and difficult to work. The watery glue-liquor is first drawn off, and
the fat which comes last is caught by itself. The thin glue-liquor is
evaporated in vacuum.

3. EXTRACTION OF BONES.

To avoid the loss of glue-yielding substance which is unavoidable in
steaming bones, even if only for a short time, in many plants the
fat is now extracted by treating the bones with benzine or carbon
disulphide. No loss of glue-yielding substance being involved by this
process, bones thus treated yield the best quality of animal charcoal.

The fat obtained by extraction with carbon disulphide has such a
disagreeable odor as to render it almost worthless. In addition this
solvent is very volatile, consequently very inflammable, and is also
very poisonous. For these reasons its use for the extraction of fat has
been almost entirely abandoned.

Figs. 31 and 32 show an apparatus for the use of benzine which is
the invention of Messrs. Wm. Adamson and Charles F. A. Simonis,
of Philadelphia, Pa. It is for the purpose of treating animal and
vegetable substances with hydrocarbons for extracting therefrom oily,
fatty and resinous matter; and the object of this invention is to
cause hydrocarbons to trickle through such substances instead of
flooding the same, so that it will take up the oily, fatty and resinous
matter without any of the albuminous or gelatinous ingredients.

Fig. 31 is a vertical section of apparatus wherewith this invention may
be carried into effect; Fig. 32, an inverted plan view of part of Fig.
31.

[Illustration: FIG. 31.]

[Illustration: FIG. 32.]

_A_ is a vessel, preferably of cylindrical form, and containing an
upper perforated diaphragm, _a_, and lower perforated diaphragm, _b_,
the former having a central opening, through which the material to be
treated may be introduced between the two diaphragms, and this opening
having a detachable perforated cover, _d_.

On the top of the vessel there is an opening, _e_, furnished with a
detachable cover, _f_, and at the bottom of the vessel there is an
outlet-pipe, _h_, furnished with a suitable cock or valve, _i_.

Liquid hydrocarbon, preferable such as is of a volatile
character—benzine, benzole, or gasoline, for instance—is introduced
into the vessel above the diaphragm _a_ through a pipe, _H_, and
perforated ring, _I_, or otherwise, the hydrocarbon passing through
the diaphragm and falls in a shower on the substance contained in the
vessel.

The hydrocarbon will trickle through the mass, taking up whatever oily,
resinous, or fatty matter it comes in contact with until it falls
through the lower diaphragm into the space _D_, whence it may be drawn
off from time to time through the outlet-pipe, _h_.

In extracting oily, fatty, or resinous matter from vegetable or animal
substances by hydrocarbons, it has been the practice either to subject
them to hydrocarbon vapors, or to immerse or steep the substances in
hydrocarbon until the latter takes up the oily, fatty, or resinous
matter.

The vapor plan is preferable in treating wet animal substances, such as
offal; but for dry vegetable or animal matter—seeds, for instance, or
the residuum resulting from the rendering of tallow—we prefer the plan
before described.

The flooding or steeping of animal or vegetable matter in liquid
hydrocarbon results in a mixture or emulsion of gelatinous, albuminous,
and fatty or oily matter, combined with animal or vegetable tissues,
the whole forming an amalgamated mass; hence, whatever fatty or oily
matter is extracted is accompanied by more or less of the suspended
gelatine or albumen, either of which is more difficult to remove from
the oil or fat, and has a tendency to discolor the same.

This difficulty, it has been found, can be obviated by preventing the
hydrocarbon from remaining in a quiescent state in contact with the
material; in other words, by causing it to trickle through the mass,
which, by this plan, retains its granular condition, and gives out its
oil or fat to the hydrocarbon without the albuminous or gelatinous
matter.

In the apparatus before described, for instance, an occurrence of the
objectionable flooding of the material, tending to bring about the
results previously mentioned, is obviated by never permitting the
extract in the lower portion of the vessel _A_ to reach the lower
diaphragm _b_. By drawing off the extract from time to time, any
impediment to the free discharge of the hydrocarbon with such oily and
resinous matter as it has taken up, through the lower diaphragm, is
prevented, and a continuous dripping of the hydrocarbon through the
mass secured.

The extract obtained by the trickling or filtering process is much more
concentrated than that obtained by the steeping and flooding process.

_Adamson’s Method for Treating Substances with Hydrocarbon Vapor
for the Purpose of Extracting Oils, Fats, etc._ This improvement is
intended to prevent the fetid or other odors imparted to the vapor
from the substances treated from being recommunicated to the said
substances, and to the extracts obtained therefrom through the medium
of the vapor from the re-used hydrocarbon. The vapor is obtained from
benzine, benzole, etc.

Fig. 33 represents, partly in section, the apparatus whereby the
invention may be carried into effect.

_A_ is a vessel in which the substances have to be treated by
hydrocarbon vapor, the said substances being introduced into the vessel
through a manhole, _x_, and deposited on a perforated diaphragm,
_B_, the manhole being provided with a suitable cover. A steam-coil,
_D_, is placed in the vessel in a space beneath the diaphragm, and
liquid hydrocarbon is introduced into the said space, and is there
vaporized by the steam-coil. The vapor rising through the perforated
diaphragm permeates the substance upon the same, so as to extract
therefrom the oily, fatty, or resinous matter, which passes downward
through the diaphragm into the space below the same, whence it may be
drawn off from time to time through the discharge-pipe _j_. Liquid
hydrocarbon may be introduced from a tank, or from a source explained
hereafter, into the top of the vessel _A_, so that it will pass through
the material and be vaporized when it reaches the coil; the said
material being in this case subjected to a downward current of liquid
hydrocarbon and an upward current of vapor.

Previous to this invention it was Mr. Adamson’s practice to cause the
vapor, after acting upon the substances in the vessel, to pass through
a worm in a condenser, the lower end of the worm communicating with the
vessel, _A_, beneath the diaphragm, as shown in Fig. 35, p. 85, so that
the hydrocarbon was used over and over again. But in practice this has
been found objectionable in many cases for the following reason:—

In treating animal offal, for instance, for the extraction of fats,
fetid odors are imparted to the hydrocarbon vapor, and remain, to a
considerable extent, in the condensed vapor when the latter is restored
to the vessel _A_; hence, the fetid odors were recommunicated both to
the fatty extracts and to the material. The same objections have been
experienced in treating meat for preservation and vegetable matter for
the extraction of oil by hydrocarbon vapor.

This difficulty is obviated in the following manner: The vapor-pipe
_D´_ communicates with a vessel _H_ at the top of the same, and the
vapor is met by numerous small jets of cold water—in the present
instance, from a perforated tubular ring, _m_, into which the water is
forced through a pipe _n_.

Many different appliances may be used, such as roses, revolving jets,
etc., for causing a spray through which the vapor must pass, and by
which it must be condensed. The result of this will be a supply, _I_,
of tainted water on the bottom of the vessel, _H_, and a quantity, _J_,
of washed and purified hydrocarbon above the water, the latter having
taken up the fetid odors.

The washed hydrocarbon may be drawn off through a pipe, _g_, into any
suitable vessel, and thence introduced through the pipe _h_ into the
vessel _A_, or may pass directly into the latter to be again vaporized
therein, the vapor after permeating the material and passing through
the pipe _D´_ being simultaneously condensed and washed in the vessel
_H_, preparatory to being returned in the condition of purified liquid
hydrocarbon to the vessel _A_.

[Illustration: FIG. 33.]

By the practice of this process, the inventor is enabled to obtain a
purer extract than heretofore, and, at the same time, the substances
acted upon are more free from noxious odors.

Changes may be made in the apparatus shown in Fig. 33, as, for
instance, the vessel _A_ may consist of a horizontal hollow cylinder,
and the vaporizing of the hydrocarbon may be accomplished otherwise
than by a steam-coil.

[Illustration: FIG. 34.]

_Adamson’s Method for Treating Substances with Liquid Hydrocarbon for
the Purpose of Extracting Oils, Fats, etc._ This invention relates
to a method of treating animal and vegetable substances with liquid
hydrocarbons, such as benzene, benzole, etc., for the purpose of
extracting from such substances oils, fats, etc.

The object of this improvement is to prevent the fetid and other odors
imparted to the liquid hydrocarbon by the substances treated from being
recommunicated to the substances and to the extracts therefrom by the
liquid hydrocarbon when re-used.

In Fig. 34, there is shown a sectional view of apparatus whereby this
invention may be carried into effect.

_A_ is a vessel into which the substances to be treated are introduced
through a manhole, _x_, provided with a suitable detachable cover,
and through an opening in the upper perforated diaphragm, _B_, a
detachable perforated plate, _b_, being placed over the opening after
the substances have been passed through the same, the substances being
supported by the lower perforated diaphragm, _B´_, beneath which is a
space for receiving the extract and liquid hydrocarbon after the latter
has percolated through the mass in the vessel. The extract, which
occupies the lowest position in the vessel, may be removed therefrom
from time to time prior to being purified by distillation or otherwise.
The liquid hydrocarbon is permitted to pass from time to time through a
pipe, _d_, into a vessel, _D_, where it is met by jets of water from a
pipe, _f_, the hydrocarbon and water being thoroughly agitated in the
vessel by a revolving paddle-wheel, _E_. This washing of the liquid
hydrocarbon may be accomplished by different appliances. For instance,
the paddle-wheel may be dispensed with, and water forced upward into
the vessel from below in the form of numerous small jets. The water and
hydrocarbon after this washing operation are permitted to pass into
the subsiding-vessel, _H_, the hydrocarbon being above and the water
below, the fetid and other odors divided by the hydrocarbon from the
substances in the vessel, _A_, having, during the washing operation,
been transferred to the water, which may be drawn off from time to time.

The washed and purified hydrocarbon may be pumped directly through
a pipe, _m_, into the vessel, _A_, to be re-used for treating the
substances therein; or it may be pumped, first, into a reservoir, and
permitted to flow from the same into the said vessel, _A_.

More or less hydrocarbon is wasted by being drawn off with the extract,
and to make up for this loss a supply may be introduced at intervals
from a tank through the pipe, _h_.

By the practice of the process described above, the inventor is
enabled to obtain a purer extract than by the ordinary process of
treating substances with liquid hydrocarbon. At the same time the
substances treated will be much more free from noxious odors than when
the hydrocarbon is used over and over again without washing.

It is not essential strictly to adhere to the apparatus shown in Fig.
34, as the construction of the apparatus will, in fact, depend in a
great measure on the locality in which it is to be situated.

_Adamson’s Process for Removing Hydrocarbons from Substances which have
been treated therewith._ This process consists of washing from animal
and vegetable substances the hydrocarbon which they retain after being
treated therewith for the extraction of oils, fats, etc., and for other
purposes.

Different apparatus may be employed for carrying out this process, and
it may be conducted in the same vessel in which the material is treated
with hydrocarbon.

The vessel, which is shown in Fig. 35, has been found to answer well
for this purpose.

This vessel is furnished with a suitable detachable cover, _a_, and
with two perforated or wire-gauze diaphragms, _b_ and _d_, both
extending across the interior of the vessel, one near the top and the
other near the bottom of the same.

A steam-coil, _B_, communicating with any adjacent steam-generator,
is contained in the vessel below the lower diaphragm, to vaporize
the hydrocarbon, the vapor passing through the substance between the
two diaphragms and out through a pipe, _D_, which passes through a
condenser, _E_, the latter restoring the hydrocarbon to a liquid form,
in which it is reconveyed to the vessel through a pipe, _D´_.

In practicing the washing process a pipe, _m_, to introduce water
into the vessel, and one or more outlet-pipes, _n n´_, two in the
present instance, are necessary. There may also be a pipe, _p_, through
which air can be introduced into the vessel, under the circumstances
explained hereafter.

When the treatment of the material in the vessel with hydrocarbon
vapor or liquid hydrocarbon has been completed, steam is cut off from
the coil _B_, the pipes _D_ and _D´_ are closed, and the cover _a_ may
be removed.

[Illustration: FIG. 35.]

Water is now admitted through the pipe _m_ to the space in the vessel
below the diaphragm _d_, and the cocks of the outlet-pipes _n n′_ are
opened.

The water permeates the material, passes upward through the same, and
carries with it the hydrocarbon, the latter having a tendency to rise
with the water.

As the water, and whatever hydrocarbon accompanies it, pass through
the upper diaphragm, _b_, the hydrocarbon will at once rise to the
surface, and will pass through the upper outlet-pipe, _n_, into
any suitable receptacle, the water passing off through the lower
outlet-pipe.

If this mode of separating the hydrocarbon from the water is practiced,
the admission of water to the vessel should be such in respect to the
outflow that the liquid will remain at or near a uniform level, that
is, the surface of the liquid should bear the relation shown in the
drawing to the upper outlet.

The water and hydrocarbon, however, may be drawn off indiscriminately
into a suitable receptacle, and then separated by decantation; but it
is advisable in all cases that the water should extend above the mass
of material in the vessel, so that the hydrocarbon can at once rise to
the surface as it escapes from the substance.

When the material is of such a character as to be closely packed
and not easily displaced by the upwardly-flowing water (and this
is especially the case with seeds which have been treated with
hydrocarbons), it is necessary to agitate the mass, so that the water
can gain access to every part thereof. This agitation the inventor
prefers to effect by air under pressure introduced through a pipe, _p_,
although mechanical appliances may be used for the purpose.

It will be understood that the process may be conducted in a vessel
separate from which the substances have been treated with hydrocarbon.
A vessel similar to that shown, for instance, but without the coil and
pipes, _D D´_, may be used, and may be furnished with trunnions (shown
by dotted lines) and adapted to bearings, so as to be easily tilted
when its contents have to be removed; or the vessel may have an opening
near the lower diaphragm for the withdrawal of its contents, a suitable
detachable door being adapted to the opening.

_F. Seltsam’s apparatus._ In this process the solvent is boiled with
the bones, previously coarsely crushed and the dust sifted out, in a
strong closed vessel, so as to obtain a higher temperature, greater
penetration and avoidance of loss. The vapor ascending condenses in the
pores, extracts the fat and collects under the false bottom as a layer
of solution which is subsequently distilled. The apparatus is shown
in Fig. 36. The cylinder, _A_, is capable of withstanding a pressure
of 10 atmospheres, and serves for the generation of steam and as an
extracting vessel. It is filled with bones and hermetically closed.
The required quantity of solvent is then brought by means of the pump,
_B_, from the reservoir, _C_, through the pipe, _D_, into the cylinder,
_A_, and the latter is heated. The vapors formed force the air through
the pipe, _E_, into the condenser, _F_, where any vapor which may be
carried along is condensed and passes through the pipe, _G_, back into
the reservoir, _C_.

[Illustration: FIG. 36.]

When all the air has been expelled from the apparatus and the pores
of the bones, the cock on the pipe, _E_, is closed. The cylinder,
_A_, is then heated so that a pressure of a few atmospheres prevails
in it. The vapors now act energetically upon the bones, the dissolved
fat collecting upon the cylinder; the cock on the pipe, _H_, is then
opened, and the superheated fluid discharged under high pressure into
the distilling apparatus, _J_, and the solvent is distilled off from
the fat by means of steam. The vapors of the solvent pass through
the pipe, _K_, into the condenser, _F_, and from there back into the
reservoir, _C_.

When the manometer on _A_ indicates no pressure, the cock on the pipe,
_H_, is closed and the cylinder, _A_, again heated, the pipe, _E_,
being open, so that any solvent still adhering to the bones may escape
to the condenser, _F_.

[Illustration: FIG. 37.]

Figs. 37 and 38 illustrate Seltsam’s apparatus as improved by Th.
Richter, whereby the operation becomes entirely free from danger, the
vaporization of the solvent being effected by steam only, and the work
is carried on continuously.

There are two extracting vessels, _A_ and _B_, of thick boiler-plate,
and provided with false bottoms, _G_, upon which the bones are placed,
steam being admitted into the space between the true and false bottoms.
The extracting vessels are surrounded by the jackets, _C_, and are
further provided with the vacuum gauges, _E_, and the air-cocks, _F_.

There are, in addition, two other vessels, _H_ and _J_, which contain
water, a vessel, _K_, for the solvent, and an air-pump, _L_. The
operation is carried on as follows:

[Illustration: FIG. 38.]

The extracting vessels, _A_ and _B_, are charged with bones, all the
cocks, with the exception of _M_ and _N_ closed, and the air-pump,
_L_, is set in motion, whereby a vacuum is formed in _A_. When this is
sufficiently large, water is admitted from _H_ through the cock _O_
into the space _P_. The water-cock is then closed and the steam-cock,
_Q_, opened. The steam entering the space, _R_, brings the water in
_P_ to the boiling-point, and the air-pump sucks off the steam formed
after the cock, _N_, is opened. The air-pump is then stopped and all
the cocks closed, except _S_. The solvent now passes from the vessel,
_K_, into the space _P_, and after closing the cock _S_, is evaporated
by the admission of steam into _R_. The water-cock is then opened and
cold water admitted into the jacket _C_, the solvent saturated with fat
being thereby condensed in _P_. The water is then discharged from _C_
and steam introduced into _R_{1}_, whereby the solvent is evaporated
and forced into the extracting vessel _B_ by means of the air-pump,
_L_, after closing the cocks _M_ and _V_.

The process is then repeated in _B_, after a vacuum has been created in
the same manner as in _A_.

In the meanwhile the vacuum in _A_ is interrupted by opening the
air-cock _F_ and the fat drawn off through _P_ by opening the cock _U_.

The bones freed from fat are removed through the manhole _D_, and _A_
is charged with fresh material while the operation is carried on in
_B_. Thus the operation is continuous, the solvent passing without any
loss whatever from one extracting vessel to the other.

[Illustration: FIG. 39.]

Alfred Leuner’s apparatus. Fig. 39, works on the Soxhlet principle,
without pressure, using solvent and steam simultaneously. The bones are
placed in _A_ above the perforated false bottom _B_. _D_ is a steampipe
by means of which the bones are steamed as a preliminary, the surplus
steam escaping through the outlet pipe _E_. After steaming, water and
benzine are run in from the reservoir _F_, into the space under the
false bottom, and heated by the steam coil _P_. The vapors evolved
are condensed in the worm _K_, and at first run back over the bones
through the cock _L_, the vapor passing upwards to the worm through
_R_, and the condensed liquid being divided into separate streams by
the spreading plate _O_. After some time the cock _G_ is opened so that
the condensed liquid runs into the reservoir _F_, instead of flowing
back into _A_. When all the solvent has volatilized nothing but water
condenses in the worm, which is known by means of a sampling cock
attached to _A_, the draw-off cock _E_ is then opened and the watery
gelatinous solution and oily matter run off into a suitable separating
receptacle. The bones in _A_ are then discharged through a manhole, and
_A_ being refilled, the whole operation is repeated.

_Extraction with hydrochloric acid._ If the bones are to be chiefly
worked for glue, extraction with hydrochloric acid, which has been
referred to in Chapter III, under “Bones and Cartilages” may be
highly recommended, the bones being thereby freed from their mineral
constituents and the glue-yielding substance remaining behind in a
pure state. The bones are allowed to remain in contact with the acid
till they are flexible and translucent. This may be readily recognized
by laying upon the material in the vat a bone split in two. When the
latter by the treatment with acid shows the characteristic appearance
of swollen cartilage, _i. e._, has become translucent, extraction may
be considered complete.

The solution is then drawn off through a tap immediately above
the bottom of the vat into stoneware vessels, and conveyed to the
evaporating pans. The tap is then closed and enough water to cover the
cartilage is admitted into the vat, and the whole allowed to stand for
a few hours in order to extract as much as possible the solution of
bone-salts remaining in the cartilage. The fluid is then drawn off. It
is a quite concentrated solution of bone-salts and, mixed with an equal
volume of hydrochloric acid, may be used for the extraction of fresh
quantities of bones, or be mixed with the fluid first drawn off and
evaporated.

The further washing of the cartilage is effected by repeatedly pouring
water over it, the operation being continued until the water running
off shows no acid reaction. Washing has to be done very carefully,
since glue-solution obtained from cartilage containing but a very small
quantity of acid will not congeal. It is, therefore, advisable to add
to the last wash-water 1 per cent. of soda, this quantity being quite
sufficient for the neutralization of the last traces of acid.

_Sulphurous acid process._ In this country sulphurous acid is largely
employed in the manufacture of glue derived from bones. When ordinary
bones are treated with a current of moist sulphurous acid gas, they
absorb from 10 to 12 per cent. of their weight of the gas in the
course of 12 hours. The amount may increase to 15 or 20 per cent.
on longer treatment, but the excess will then disappear on exposure
to air. Messrs. Grillo and Schroeder of Düsseldorf, who patented
this process in 1894, believe that this is simply due to the calcium
phosphate present in the bones, and remark that an absorption of 11 to
12 per cent. on the gross weight amounts to 16 or 17 per cent. of the
inorganic constituents, and corresponds to the equation:

Ca_{3}(PO_{4})_{2} + SO_{2} + H_{2}O = 2CaHPO_{4} + CaSO_{3},

the sulphurous acid simply acting in the same way as sulphuric acid
does in the manufacture of superphosphate, but being a milder acid
than sulphuric, the alteration of the organic constituents which are
available for glue-stock can be almost entirely avoided. The acid
phosphate is soluble in water, therefore the bones after treatment are
easily disintegrated by boiling water when a large portion of the lime
remains in the sediment, while the gelatine is dissolved.

The process as commercially conducted is very similar to the well-known
sulphite method of treating paper pulp, and is carried on in iron
cylinders or better in close wooden vats lined with lead.

[Illustration: FIG. 40.]

The gas is usually generated in an impure form, with a large admixture
of air and carbonic acid, by combustion of pyrites and coal, of crude
sulphur, or even of only highly pyritous fuel.

On the other hand, since it is well established that the absorption of
a diluted gas is less ready, and is more wasteful than that of a gas in
a pure state, the employment of a definite quantity of sulphur dioxide
in a concentrated state, either prepared by the regulated burning of
sulphur, or the decomposition of sulphuric acid, yields more regular
results, and a product of better quality. Liquid sulphur dioxide,
which is now obtainable at a moderate price and in quantity, has the
advantage that it yields a continuous current of pure gas of any
required rapidity by simply opening a valve, and that the exact amount
used can be ascertained by taring the containing vessel before and
after the operation (S. Rideall).

The washed bones are brought into the above-mentioned cylinder or vat
and treated with a saturated solution of sulphurous acid. The duration
of the action of the acid varies according to the condition of the
material and can only be determined by experience. The result of the
process is a liquor almost as clear as water, which, after evaporation
in the vacuum pan, is equal as regards clearness and lustre, to the
best quality of glue prepared from waste of hide and skin. The fat
extracted from the bleached bones is lighter in color and has not the
disagreeable odor of ordinary bone fat, and consequently brings a
better price.

For the generation of sulphurous acid Dr. Bruno Terne, of Mass., has
constructed a very simple apparatus shown in Fig. 40. The sulphur is
burned in _S_; _A_ is the escape pipe of stone; _T_, the collecting
reservoir; _P_, the steam-pump for acid; _R_, chimney for the sulphur
burner.

4. CONVERSION OF CARTILAGE INTO GLUE.

The conversion into glue of the swollen cartilage obtained by treatment
with hydrochloric or sulphurous acid may be effected by continued
boiling in open pans or in an apparatus recommended by Wm. Friedberg,
and shown in Fig. 41.

The boiler _K_ of thick boiler-plate has a diameter equal to its
height. Underneath the perforated false bottom _S_, which serves for
the support of the bones, lies a perforated steam coil _R—D_ for the
introduction of steam. To this steam coil is fitted a branch-pipe
_d_, which reaches into the upper portion of the boiler into which
also enters the water-pipe _W_. The apparatus is further fitted
with a water-gauge, an air cock, sampling cock and manhole for the
introduction of the cartilage.

[Illustration: FIG. 41.]

The mode of operation with this apparatus is as follows: The boiler is
filled three-quarters full with cartilage. Enough water to fill the
boiler one-quarter full is then admitted through the pipe _W_, and
the steam-cock _D_ opened. The steam passing out through the numerous
perforations in the coil _R_, is at first condensed in the water, but
soon brings the latter to the boiling-point, and from this stage on
begins the formation of glue. The glue dissolves in the water, and
a sample of the solution is from time to time drawn off through the
sampling cock and tested as to its concentration. When the solution
possesses the required concentration, the admission of steam through
_R_ is interrupted, and the cock _d_ of the branch-pipe opened, as
well as the cock of the discharge pipe _H_, the latter being opened
gradually. The discharge pipe _H_ is connected with the perforated
plate _F_, which is covered with a closely-woven cloth and thus acts
as a filter, retaining all the solid particles suspended in the glue
solution.

By opening the cock _d_ of the branch-pipe, the steam-pressure acts
only upon the surface of the fluid, the latter being consequently
pressed with great force through the filter-cloth.

When the hissing noise caused by escaping steam indicates that all the
fluid has been removed from the boiler, the cock _d_ of the branch-pipe
is closed, and through a rose fitted above the boiler, water is allowed
to flow upon the latter. By this cooling the greater portion of the
steam in the boiler is condensed and water may be admitted through _W_.

[Illustration: FIG. 42.]

The operation of glue-boiling is then commenced anew by admitting
steam into the steam coil, and continued until the cartilaginous mass
has been reduced to about one-third of its original bulk, when the
apparatus is opened, fresh material introduced, and the whole operation
repeated.

In order to be able to replace the filter without having to empty
the entire apparatus, it has been given the shape shown in Fig. 42.
The upper portion of the discharge-pipe _A_ is connected with the
lower portion by the box-screw _H_. In the latter is inserted a short
cylinder, _C_, with a perforated bottom upon which is placed the
filter-cloth; the latter is kept in position by the ring _R_.

[Illustration: FIG. 43.]

For every apparatus two of the above-described filters will be
required. If, notwithstanding a full steam pressure, the glue solution
runs off sluggishly, it is indicative of the pores of the filter being
choked up. The screw-box _H_ is then removed, the filter taken out and
replaced by another one.

The glue solution discharged from the apparatus is in most cases
sufficiently clear to allow of its being immediately evaporated.
However, for the production of a particularly fine quality of glue,
it is advisable to clarify the solution by settling. As the liquor
has to be kept warm to allow of the solid particles to settle, W.
Friedberg recommends the use of the apparatus shown in Fig. 43. It
consists of an iron cylinder with a diameter equal to one-third of its
height. The front of the cylinder is furnished with a number of cocks
placed at equal distances from each other, and also with a pipe in
the slightly conical bottom. It is surrounded by a wooden jacket, the
intermediate space being filled with a bad conductor of heat. By this
arrangement the liquor is kept warm and in a liquid state for several
hours, giving ample time for the solid bodies held in suspension to
settle on the bottom. The condition of the liquor is from time to time
tested by allowing a small quantity of it to run into a glass from the
lowest cock in front. If the sample is perfectly clear, the liquor
may be drawn off. If, however, after several hours’ standing only the
upper portions of the liquor are clear, while the lower ones are still
turbid, further clarification by this means is impossible. The upper
portions of the liquor are then used for finer qualities of glue and
the lower ones for inferior grades.

By treating the cartilage with high-pressure steam, a liquor is
obtained which on cooling congeals to quite a solid jelly, and it might
be immediately brought into the forming-boxes, cut into cakes, and
dried. However, as the drying of the glue is one of the most difficult
operations for the glue-maker, it is of great advantage to obtain the
liquor in as high a state of concentration as possible in order to
obtain a solid jelly, which causes the least difficulty in drying. For
this purpose the liquors leaving the clarifying vat with a strength of
about 20 per cent. dry glue are evaporated down to a strength of about
32 per cent. in winter, and 35 per cent. in summer. Evaporation may be
effected in open pans or in vacuum.

Fig. 44 shows the arrangement of an open evaporating pan. The copper
pan _P_ has the form of a shallow cylinder with a slightly conical
bottom, in the lowest point of which is the discharge pipe for the
concentrated liquor. During the operation the discharge pipe is closed
by the ball-valve _V_, which can be raised by the lever contrivance
_M_. The pan is surrounded by an iron steam-jacket; the steam passes in
at _D_, and the condensed water runs off at _A_. _H_ is a sampling cock
for taking samples to test the concentration of the liquor.

[Illustration: FIG. 44.]

To prevent the workroom from being filled with steam arising from the
pan, the latter is covered with a hood of wood which terminates in the
pipe _S_ projecting above the roof, and a narrow pipe _R_ branching off
from the steam pipe _D_ passes into _S_.

When vapors commence to arise from the liquor, the cock on the pipe _R_
is slightly opened whereby a jet of steam is blown into the pipe _S_,
the latter then acting as an exhauster, and the vapors in the hood _C_
are carried along by the jet of steam. By this arrangement no vapor
passes into the workroom and steam is also very rapidly evolved from
the surface of the liquor.

Sufficient steam should be admitted to the pan for the liquor to give
out an abundance of vapor without, however, being brought to the
boiling-point, as in that case foam would be formed and the liquor in
cooling yield a product full of blisters. When the liquor has acquired
the proper degree of concentration, the admission of steam to _D_ and
_R_ is interrupted and the valve _V_ having been raised the liquor is
run into the cooling-boxes. The latter are of wood lined with zinc, or
better of stout zinc or heavily galvanized iron. They hold about ½ cwt.
and are of two shapes: one deep and nearly square, another long and
shallow, for quick cooling of clear liquors. Iron should not be used,
as it readily rusts and causes discoloration of the glue.

Cooling is effected by cold water where it is available, but often
merely by cold air, aided by fans or blowers, in a room protected from
heat or frost. According to S. Rideal, refrigerating machines are now
also employed, which, by the evaporation of liquid gases, such as
ammonia, sulphurous or carbonic acid, reduce a tank of brine to near
freezing-point. The temperature should not be allowed below 33° or 34°
F., for if frozen the jelly is hard and difficult to cut. The brine
circulates in iron pipes placed near the ceiling of the room; they must
be kept as clear as possible of ice and dirt, and the cooling house
should be scrupulously clean and sweet.

Spiral evaporators are recommended by Thomas Lambert as forming a ready
and economical means of evaporation. The evaporator consists of a
spiral steam coil, made of copper, and 2 inches in diameter, revolving
on a centre shaft; the lower half of the coil is covered with the
glue-liquor in the trough. The shaft rests on two plummer-blocks, one
receiving the steam, and the other discharging the spent steam and
condensed water. The shaft is hollow to the first coil, and the steam
is thus conveyed to the spiral. From the last coil to the end of the
plummer-block the shaft is also hollow, and in that portion resting on
the block two openings are made. In the inside of the plummer-block,
two openings are bored to the outside, each forming a covered channel;
as the shaft revolves, all the holes directly face each other at
intervals, and thus allow any condensed water in the coils to be blown
through. From 25 to 28 coils are generally used in each spiral. The
glue-liquors are fed into the trough at one end, and have a temperature
of 75° F.; the temperature of the evaporated liquor is 85° F. In the
rather slow passage through the trough, the liquors receiving the heat
of the revolving coils are raised in strength from 20 per cent. to 32
per cent. dry glue, at which point they are ready for jellying.

_Vacuum pans_ are much used in this country for evaporating
glue-liquors, though there are some complaints made of the great waste
owing to spray and froth being carried off in the steam. As is well
known the boiling-point is lowered by increasing the pressure on the
surface of a fluid. By enclosing water in a vessel connected with a
constantly working air-pump, it is brought to the boiling-point by
heating to between 95° and 104° F. The construction of vacuum pans is
based upon this principle, and such apparatus is largely used in many
manufacturing processes for evaporating to a certain degree fluids, for
instance, sugar solutions, which readily become decomposed at a higher
temperature. Vacuum pans are also very suitable for the evaporation of
glue-solution, especially in plants working on a large scale.

Fig. 45 represents an elevation of a vacuum pan for evaporating glue
and gelatine liquors as described by Thomas Lambert. The pan is built
of steel plates, and lined outside with wood work, and rests on a
floor constructed of rolled steel plates, supported on four columns,
with a stairway leading to the working platform. One half of the
lower part is shown in section, giving a view of the coils by which
the pan is heated. The various parts are as follows: _A_, the body of
the pan; _B_, the dome; _C_, exhaust pipe leading from the dome to
the condenser; _D_, condenser; _E_, air or vacuum pump; _F_, storage
tank for glue or gelatine liquors, warmed with steam coil; _G_, supply
pipe leading from storage tank to vacuum pan; _H_, discharge valve;
_I_, barometer gauge for indicating vacuum; _J_, inlet steam pipe
for supplying the coils; _K_, exhaust end of vacuum coils; _L_, iron
staircase; _M_, steel floor.

[Illustration: FIG. 45.]

The accessories to the pan are placed in a convenient position above
the working floor and include a steam gauge for noting the pressure in
the coils, a gauge for indicating the height of the liquor in the pan,
vacuum gauge _I_, as shown in the drawing, air-cocks and a thermometer.
The pan is also fitted with a small apparatus, by which portions of the
boiling liquor can from time to time be drawn, without disarranging the
vacuum, so that the progress of evaporation can be ascertained.

In working the pan, the storage tank _F_ is first filled with the weak
glue liquors to be evaporated; the valve on the supply pipe _G_ is then
closed, and the vacuum pump set in motion; a few strokes are sufficient
to reduce the internal pressure, and the valve of the supply pipe is
then opened, and the liquor allowed to fill up the pan to the desired
mark on the gauge. The valve is then closed, the steam-inlet valve _J_,
supplying the coils, opened. As the heat from the coils spreads through
the liquor, the vacuum pump is kept steadily at work reducing the
inside pressure to within 2 to 2½ inches of a perfect vacuum, as seen
on the barometrical scale. In this vacuum the liquor will boil at 120°
to 130° F., and the boiling is continued until the withdrawn samples,
as tested by the glue-meter, show the desired strength. The pump is
then stopped, the vacuum broken by opening the air-cocks, and the
concentrated liquor is run through the valve _H_ into suitably arranged
receiving tanks, for supplying the trays or glasses for jellying.

For economical working with large quantities of weak liquors, a
combination of two, three and even four vacuum pans, forming the
double, triple and quadruple effect evaporators, have been designed
for concentration purposes. The triple effect is, however, the system
mostly in use, and consists of a grouping of three cylindrical pans,
each connected by suitably arranged piping, by which the vapors of the
first pan are conveyed to and made to heat the coils of a second pan,
the resulting vapors from the second, passing on to the third pan, for
a similar purpose. All the pans are connected with powerful pumps,
producing a nearly absolute vacuum in each. The liquor is evaporated to
a given density in the first pan, and then passed on to the second, and
ultimately to the third, at which stage 80 per cent. of its water will
have been driven off.

To obtain in all cases a product of equal concentration, it is
advisable to have an instrument which will indicate the amount of dry
glue in the solution. (Fig. 46.)

By immersing a glass aerometer in the glue-liquor, the percentage of
glue is indicated by a scale registering from 0 to 70 per cent. with
the jelly or glue solution at a temperature of 167° F.

To measure the temperature quickly, a thermometer is added, and for
the execution of the entire test, a sheet-iron vessel consisting of
a large and two small tubes, _a_, which when not in use, serve for
the reception of the glass instruments contained in a special case.
For testing, the small cylinder is placed in the large tube, _a_, and
filled with jelly by means of the cap which serves as a cover. The
large tube is filled with hot water to bring the jelly to the required
temperature. The two instruments are then immersed in the tubes filled
with glue-liquors to be tested, and temperature as well as percentage
can be readily read off.

[Illustration: FIG. 46.]

The evaporated and cooled glue-liquor is cut into cakes and dried in
the same manner as previously described.

5. PROCESS FOR THE SIMULTANEOUS UTILIZATION OF BONES FOR FAT, BONE-MEAL
AND GLUE.

Manufacturers frequently sort the bones in such a way that materials of
different quality are obtained. Thick, compact bones are utilized for
the manufacture of animal charcoal, a comparatively small percentage
of bone-meal resulting in crushing such bones.

Incompact, porous bones, on the other hand, yield not only crummy
animal charcoal of less value, but in stamping also a larger percentage
of bone-meal than compact bones. Hence they are as a rule directly
worked for fat, glue and steamed bone-meal, no attempt being made
to convert them into such granular pieces as are suitable for the
production of charcoal.

For this purpose, the bones are first broken by a crusher or mill into
coarse pieces, and the fat extracted by a special process or together
with the glue in one operation. The latter method would seem to be the
most suitable, time and labor being thereby saved, but it must be borne
in mind that fat extracted by itself brings a much better price than
that obtained by steaming, and besides the yield of glue is larger from
steamed bones which have been previously degreased.

The crushed bones—whether degreased or not—are subjected to the action
of high-pressure steam. The apparatus, Fig. 47, used for this purpose
consists of a cylinder of thick boiler-plate, 10 to 13 feet high and 3
to 4 feet in diameter. _E_ and _A_ are manholes, which can be closed
steam-tight. The pipe _D_ leads to the steam-boiler and opposite to
_D_ is a short pipe, _H_. The cylinder is further fitted with the
perforated false bottom, _S_, and the bent pipe, _L_.

As a rule, four to six, and in larger plants even more, of such
cylinders are combined to a battery. In this case the discharge pipe,
_L_, terminates in a common collecting vessel, and the steam-pipes,
_D_, branch off from a main steampipe. The battery may be enclosed by
brickwork, but is preferably placed upon a suitable foundation and
surrounded by woodwork, the intermediate space between woodwork and
cylinders being filled with sawdust. This plan offers the best means of
keeping the heat together, and the further advantage that, in case one
of the cylinders becomes defective, it can be readily taken out and
replaced by a new one.

[Illustration: FIG. 47.]

In order to be able to fill the cylinders rapidly and with the least
expenditure of power, it is advisable to place the bone-crusher at such
a height that the crushed bones fall directly into carriages which are
run upon a small railway over the charging holes of the cylinders, and
emptied. In front of the manholes, _A_, for discharging the bones is
also a railway, so that the crushed bones can be directly emptied into
carriages and conveyed to the stamping mill.

The cylinder having been filled with bones, is closed steam-tight. The
cock, _H_, is then opened and steam admitted by opening the cock _D_.
The steam passing in at first, is cooled off by coming in contact
with the bones and condensed to water. However, the temperature in the
cylinder soon becomes so high that the steam is no longer condensed
and, having first expelled the air in the cylinder through the pipe
_H_, it escapes through the latter in the form of a powerful jet. When
this is the case _H_ is closed and high-pressure steam allowed to act
upon the bones.

The fat contained in the bones melts and trickles down. On the bottom
of the cylinder collects a fluid which contains glue, is of a milky
turbidity due to admixed drops of fat, and with a quite thick layer of
fat upon its surface. From time to time—about every hour—the cock _L_
is slightly opened. By the pressure of the steam the glue-liquor is
expelled with great force through the pipe _L_, the latter being closed
when by the peculiar noise it is noticed that only steam escapes.

Steaming and the occasional discharge of melted fat are continued until
on testing a sample of the liquor running off, it is noticed to be free
from fat. The liquor in the cylinder is then expelled by the pressure
of steam, the steam-cock _D_ closed, the manhole _A_ opened, and steam
again admitted through _D_. By the steam-pressure the greater portion
of the bones in the cylinder is expelled through the manhole _A_. The
bones coming from the cylinder are pliable and soft, and, after drying,
are readily converted by grinding into bone-meal.

For the manufacture of animal charcoal it is of the utmost importance
that steaming should be interrupted at the time when the bones are
completely degreased. If, however, only fat, glue and bone-meal are to
be produced, steaming may advantageously be continued for a longer time.

The longer the bones are subjected to the action of high-pressure
steam, the more complete the conversion of glue-yielding substance into
glue will be. To be sure, the bone-meal obtained from such bones will
contain somewhat less nitrogen than the product from bones not steamed
quite so long. However, the content of phosphates will in both cases be
the same, and on this depends, in the main, the fertilizing value of
bone-meal.

The fluid discharged from the cylinder consists of a mixture of
glue-liquor and drops of fat. It is run into a large vat, in which it
is kept warm for a few hours, when the fat rises and collects in a
coherent mass on the surface. The fat is then drawn off through cocks
in the upper portion of the vat, while the glue-liquor is discharged
from the bottom of the vat, running first upon a very fine meshed
sieve, which retains the coarser bodies held in suspension, and then
directly into the evaporator. In the latter the liquor is evaporated
to the desired strength, when it is run into the clarifying vats, and
finally into the cooling vessels.

With the above-described process, the simultaneous utilization of the
bones for animal charcoal is only possible if the crushed steamed bones
are passed through a sieve for the purpose of sorting out the granular
pieces of suitable size. However, in the process above described,
incompact bones are, as a rule, used which give but a small percentage
of granulated pieces, and the latter yield an inferior quality of
animal charcoal. It is therefore best to use the steamed bones from
which the fat and glue have been extracted for the production of
bone-meal.

For the manufacture of animal charcoal, the bones have to be carefully
sorted, fresh bones rich in organic substance being best for the
purpose, and the hardest and thickest pieces should be selected.
Previous to carbonization, the bones are degreased by extraction with
benzine or carbon disulphide, and then crushed.

Carbonization was formerly effected in iron pots having a capacity of
about 25 quarts each. However, by this process a uniform product of
good quality cannot be obtained, and, besides, the total quantity of
organic substance of the bones is lost. At present carbonization is
effected in retorts, whereby large quantities of animal charcoal are
in a comparatively short time obtained, and, besides, the products
of destructive distillation can be completely utilized. An essential
product of distillation is a large quantity of inflammable gases, which
can be used for heating the retort-furnace or for illuminating the
entire plant, it being, however, best to arrange the conduits so that
the gases can be used for either purpose.

A detailed discussion of the methods for gaining and further working
of the products of distillation is not within the scope of this work,
and only a brief description of a plant for the manufacture of animal
charcoal will here be given.

[Illustration: FIG. 48.]

Figs. 48 and 49 show the arrangement of a Belgian retort-furnace, Fig.
48 representing a vertical section lengthways, and Fig. 49 a horizontal
section. The illustrations, however, are given at different heights in
order to show plainly the arrangement of the fire-place and the passage
of the fire-gases.

The cast-iron retorts—sixteen in the apparatus shown—are placed in
rows alongside and one after another, so as to be swept as uniformly
as possible by the fire. As will be seen from Fig. 49 the firing is so
arranged that only the upper portions of the retorts are touched by the
flames. _B_ is the actual fire-place, and _A_ the ash-pit, both being
furnished with closely fitting doors so that the fire may be properly
regulated, and the retorts eventually be exclusively heated with gas.

[Illustration: FIG. 49.]

The retorts are cylindrical in form, with one end closed. At the open
end is fixed the frame or mouth-piece, which carries the door swung on
a hinge. The door has a slight projecting rim, some two inches wide,
which, with the surface of the frame, is ground perfectly true; on
closing, the joint is made gas-tight by a lever arrangement.

The fire-gases escaping from _B_ are distributed as uniformly as
possible by the flues, _a_, carried underneath the pans, _E_, and
finally pass out in the direction of the arrows through a chimney.

At the time when the extraction of fat was exclusively effected by
boiling the bones, the pans _E_ served for this purpose, and the spaces
_D_, _D__{1}, _D__{2}, etc., alongside the pans, which were also heated
by the fire-gases, were used for drying the bones. However, at present,
the extraction of fat is, as a rule, effected by means of benzine or
carbon disulphide, and it is advisable to replace the pans, _E_, by a
bonekiln, and eventually to utilize any waste heat for heating the
evaporators for glue-liquor.

Fixed to the upper portion of each retort is a pipe, and these pipes
lead into a very wide iron-pipe, _T_. The products of destructive
distillation escaping from the retorts combine in _T_, and besides
having a very large diameter, this pipe must be considerably inclined
to avoid the accumulation of products of distillation in it. To prevent
the products of distillation from depositing in a crystalline form in
_T_, the latter is covered with a bad conductor of heat.

The pipe _T_ is connected with a series of condensing vessels, _D_,
another series of vessels being placed alongside the first one, so that
the vapors may be conducted, as desired, into either one of them. Two
batteries of such condensing vessels are required, as one of them has
from time to time to be disengaged in order to be cleansed.

If the products of distillation would have to overcome the entire
pressure of the column of fluid in the condensing vessels, their escape
from the retorts would be very much retarded. To avoid this, plates are
arranged horizontally a few inches below the level of the fluid, and
the pipes dip into the condensing vessels only far enough to permit the
escaping vapors to pass under these plates. By this arrangement, the
vapors sweep under the plates and are absorbed by the fluids, a strong
pressure in the apparatus being thus avoided.

The condensing batteries may of course consist of any number of
vessels, but as a rule only a sufficient number to retain all the
ammonia is employed, five being in most cases sufficient for this
purpose. The last condenser is connected with an exhaust-pump, _p p_,
which is kept in motion by a motor, _P_.

The pump removes all the bodies remaining in the last condenser and
forces them, according to the position of the cock back of the pump,
either into a glass-bell or through the pipe _H_ and the nozzles _a_
into the fire-place where they are burned.

To obtain the various products of distillation, the condensing vessels
have to be filled with acid, and should therefore be constructed of
lead or at least of sheet-iron lined with lead. The products to be
obtained depend on the fluid used for filling the vessels; if filled
with dilute sulphuric acid, ammonium sulphate is obtained, which may
be utilized in the preparation of fertilizers. If hydrochloric acid is
employed for the absorption of ammonia, solution of ammonium chloride
is obtained, which may be crystallized by evaporation.

The products evolved in the destructive distillation of bones consist
of various hydrocarbons and appear either as badly-smelling brown
liquors—bone-tar—or as illuminating gas. The vapors contain further
considerable quantities of ammonium carbonate and cyanide of ammonium.
To obtain the latter, the last condensing vessel is filled with green
vitriol solution, the cyanogen compounds remaining behind in the
solution. If the gas escaping from the last condenser is to be used for
illuminating purposes, it is freed from the greater portion of carbonic
acid contained in it by purification with lime.

The mode of operation with Belgian retort furnaces is as follows:
The retorts having been filled with comminuted degreased bones, the
doors are closed perfectly gas-tight and firing is commenced. The pump
is set in motion until a jet of gas blows through the nozzles. When
this gas-jet burns with a luminous flame, destructive distillation of
the bones is in full blast. The pump is then run with such velocity
that the pressure in the interior of the retorts, as indicated by the
manometer, is slightly greater than the external air-pressure, and the
operation is thus continued so long as inflammable gases escape from
the pipe _H_. The pump is then stopped, and one-half of the charcoal
contained in the retorts is withdrawn to the canisters placed ready to
receive it. The lids of the canisters are then luted down with a paste
of char-dust and water, making an air-tight joint, and the charcoal is
allowed to cool.

The retorts having been partially emptied, are at once refilled to the
brim with crushed bones and closed gas-tight. There is but little or no
loss of heat between withdrawing and charging, and distillation of the
freshly-introduced bones commences immediately after charging, and is
finished in a much shorter time than in the beginning of the operation.

In making animal charcoal on a large scale there are obtained from 2000
lbs. of raw material:

Animal charcoal, 1180 to 1220 lbs.
Ammoniacal liquor, 178 to 180 lbs.
Gas, 222 to 248 cubic yards.

However, these figures refer only to bones degreased by steaming,
whereby a considerable portion of the cartilaginous substance passes
into solution in the form of glue. In working bones degreased with
benzine, larger yields than those indicated above are as a rule
obtained. The ammoniacal liquor contains on an average 10 per cent. of
ammonia. The gas freed from carbonic acid yields 2.7 times more light
than good coal-gas.

6. PROCESS FOR THE SIMULTANEOUS UTILIZATION OF THE BONES FOR FAT, GLUE
AND CALCIUM PHOSPHATE.

This process differs from the one previously described in that, in
addition to the total quantity of fat and glue-yielding substance
contained in the bones, the mineral salts are also obtained in a pure
state, and can be further utilized.

The bones are degreased either by extraction with benzine or carbon
disulphide or steaming, the operation in the latter case being
continued so long as fat is yielded by the bones. The resulting
glue-liquor is used in place of water for boiling the cartilage.

The bones are placed in large wooden vats furnished with well-fitting
lids, and hydrochloric acid of 12 per cent. poured over them so that
they are covered a few inches deep. With the use of acid of 1.04
specific gravity the greater portion of the salts contained in the
bones will pass into solution in 48 to 72 hours, when the solution is
drawn off as completely as possible from the vats.

The residue in the vats is treated with less concentrated hydrochloric
acid and left in contact with it until the bones are soft and flexible
and the thinner pieces have become translucent, this being a proof
that all the mineral salts have been extracted, and nothing but pure
cartilaginous substance remains behind. The solution is then drawn off,
and after pouring repeatedly small quantities of pure water over the
cartilage to expel the last remnants of acid liquor, it is subjected to
thorough washing until the last traces of acid have been removed.

The resulting cartilage is white, translucent, and water-soaked. If
left in this state it would of course soon putrefy, and it is best to
work it at once, or if this cannot be done it will have to be treated
with carbolic acid in the manner previously described, or dried.

Drying the cartilage is time-consuming work, and can properly be done
only by artificial heat in kilns. If carefully protected from moisture,
thoroughly dried cartilage may be kept without injury for any length
of time. However, before being worked to glue, such material has to
be again soaked in water previous to the actual boiling operation,
and this process requires considerable time. It is therefore best to
preserve it in carbolic acid solution, which only needs to be drawn off
when the cartilage is to be worked, and may be further utilized.

If boiled in open vessels with water, 6 to 8 hours are required for
the complete disintegration of the cartilage. In a closed apparatus
under high pressure solution is effected in a much shorter time and the
operation progresses very smoothly. With proper attention the glue
obtained from bones degreased with benzine and freed from bone-earth by
extraction with hydrochloric acid is, as a rule, very clear, and may be
bleached with sulphurous acid.

The extraction of the phosphates from bones may be effected in a very
suitable manner as follows: A number of vats filled with bones are
placed in terraces one above the other, and the acid is allowed to
run first into the uppermost vat. After having been for several hours
in contact with the bones it is discharged into the next vat, fresh
acid being run into the first one, and so on. By this process a highly
concentrated solution of phosphates is in a few hours obtained in the
lowest vat, solution still adhering to the bones in the other vats
being finally expelled by water.

However, the process of extraction under decreased pressure is the
most advantageous, it requiring least time. For this purpose the bones
are brought into a vessel which can be closed air-tight and the air
is expelled. When but a slight air-pressure prevails in the vessel,
the cock of a reservoir filled with hydrochloric acid is opened, the
external air-pressure now forcing hydrochloric acid into the extracting
vessel.

Bones, as viewed under the microscope, consist of a mass permeated
with numerous minute tubes or pores. When the air is expelled from
the vessel containing the bones, the air in the pores of the latter
is rarefied and the hollow spaces are filled with hydrochloric acid
whereby solution of the phosphates is effected.

The yield of glue obtained from cartilage after extraction of the
mineral constituents varies according to the compactness of the bones
used. Solid and compact bones yield, on an average, 15 per cent. of
dry glue, but a comparatively large quantity of calcium phosphate. On
the other hand, porous bones rich in cartilage yield from 20 to 25 per
cent. of dry glue. The liquor obtained by treating the bones contains,
as previously mentioned, calcium phosphate, magnesium phosphate and
calcium chloride in solution, and may be utilized in the manufacture of
fertilizers or of phosphorus.

For the first purpose which is not very remunerative, but is not
very troublesome, the liquor is treated with milk of lime until it
is slightly alkaline, whereby a finely divided precipitate of basic
calcium phosphate is obtained, whilst calcium chloride remains in
solution. The precipitate is allowed to settle, separated from the
supernatant fluid and dried. The resulting product contains, on an
average, 65 per cent. calcium phosphate, up to 20 per cent. water
and 10 to 15 per cent. calcium carbonate, quick lime and accidental
impurities. It forms an excellent fertilizer.

If the liquor is to be utilized in the manufacture of phosphorus, it
is evaporated in shallow pans of glazed stoneware. In cooling crystals
of acid calcium phosphate are formed, which are separated from the
mother-liquor. This subject will be more fully referred to in the next
chapter.

CHAPTER VI.

MANUFACTURE OF PHOSPHORUS.

In some instances the preparation of phosphorus is carried on in
conjunction with other industries, for instance, glue-boiling, the
preparation of sal ammoniac, yellow prussiate of potash, etc. Bone-ash
is the chief material used by phosphorus makers. Many manufacturers do
not burn the bones to ashes, but purchase bone-ash, large quantities
of which are brought from South America, especially from the Argentine
Republic.

The ordinary method of preparing phosphorus includes the following
operations:

1. Burning the bones and grinding the bone-ash to powder.

2. Decomposition of the bone-ash by sulphuric acid, and evaporation of
the acid phosphate previously mixed with charcoal.

3. The distillation of the phosphorus.

4. The refining and purifying the phosphorus.

_Burning the bones to ash._ The object of the ignition of the bones
is the complete destruction of the organic matter. The operation is
conducted in a kiln very similar to those in use for burning lime.
A layer of brush-wood having been put on the bottom of the kiln,
bones form the next stratum, and so on alternately. The wood having
been lighted, the combustion of the bones ensues. In order to carry
off the fumes, the smell of which is very offensive, a hood made of
boiler-plate is placed on the kiln, and either connected with a tall
chimney, or the smoke and gases are conducted into the fire of the
kiln and burnt. The white burnt bones are withdrawn through an opening
reserved in the wall on purpose, the kiln being kept continuously in
operation, as in the case with some lime kilns.

This kind of kiln, however, possesses many disadvantages, and an
improved form, as proposed by Fleck, is shown in Fig. 50.

[Illustration: FIG. 50.]

The actual combustion chamber consists of a shaft, _A_, composed of
two inverted cones. In the lowest portion of the lower cone are four
or six apertures, _b_, which terminate in inclined channels and serve
as air-flues, as well as for withdrawing the burnt bones. Through the
aperture _a_ in the upper portion of the shaft additional bones may be
introduced. This aperture is covered with a heavy iron lid.

As will be seen from the illustration, the shaft contracts towards the
top in the form of a retort and passes into a horizontal channel _B_
which is provided, near its beginning, with an ordinary fire-place _d_.
The gases and fumes escaping from the burning bones must pass over the
flame of the fire-place _d_, and are thereby so completely consumed to
water, carbonic acid and free nitrogen that no odor is perceptible even
in the immediate neighborhood of the kiln.

In order not to lose the heat yielded by the fire-place _d_ and the
burning vapors, the channel _B_ is covered with shallow pans _P_,
for the evaporation of such fluids as have to be subjected to this
treatment in the factory.

The mode of operation with a kiln of this construction is as follows:
The shaft is filled two-thirds full with bones and dry wood split in
small pieces is placed in the channels _b_ and simultaneously ignited.
Four or six long hot flames thus strike the bones, the latter becoming
in a short time so highly heated that they commence to burn briskly and
ignite fresh portions of bones introduced through the aperture _a_.

The white burnt bones in the lower portion of the kiln are withdrawn,
while in a glowing state, by means of iron hooks; the next layer of
bones sinks down and fresh material is introduced through _a_, the kiln
being thus kept continuously in operation.

The quantity of substance which remains after burning the bones depends
of course on the quality of the material used. Tubular bones of old
animals contain the largest quantity of mineral substance, and give a
much more abundant yield of bone-ash than the spongy bones of younger
animals. On an average 100 parts by weight of fresh bones yield 55
parts by weight of bone-ash. The composition of the latter is as
follows:

Basic calcium phosphate, 80 to 84 per cent.
Basic magnesium phosphate, 2 to 3 per cent.
Calcium carbonate, } 10 to 14 per cent.
Calcium fluoride, }

The bone-ash thus obtained is converted into a coarse powder by means
of machinery, a bone-mill being best suited for the purpose. Experience
has shown that the granules obtained by grinding should be the size of
lentils. With the use of larger pieces the acid, with which the ash is
treated later on, does not penetrate the entire thickness of the bone
mass and a portion of the latter remains undecomposed. If the granules
are too small, lumps are formed when the ash is brought together with
the acid, and the mass would have to be constantly stirred in order to,
make the action of the acid effective.

_Decomposition of the bone-ash by sulphuric acid._ When the basic
calcium phosphate—the constituent of the bone-ash which comes here into
consideration—is brought in contact with an acid of sufficient strength
to effect its decomposition, calcium sulphate (gypsum) is formed, and
a solution of acid calcium phosphate. If the latter be mixed with
powdered charcoal, evaporated to dryness, and the mixture exposed, with
the exclusion of air, to a strong red heat, the acid calcium phosphate
is first converted into calcium metaphosphate, water being yielded. At
this high temperature the calcium metaphosphate is by the action of the
carbon decomposed to basic calcium phosphate and phosphorus; the latter
escapes in the form of vapor and may be caught in suitable condensing
vessels.

Hence three separate processes have to be distinguished: 1. The
formation of acid calcium phosphate from the basic calcium phosphate
contained in the bone-ash. 2. The conversion of the acid calcium
phosphate into calcium metaphosphate. 3. Decomposition of the calcium
metaphosphate, phosphorus being liberated, while basic calcium
phosphate remains behind.

Expressed in chemical symbols these processes may be embodied in the
following equations:

I. Ca_{3}(PO_{4})_{2} + 2H_{2}SO_{4} = 2CaSO_{4} + CaH_{4}(PO_{4})_{2}
Basic calcium Sulphuric Calcium Acid Calcium
phosphate. acid. sulphate phosphate.
(gypsum).

II. CaH_{4}(PO_{4})_{2} = 2H_{2}O + Ca(PO_{3})_{2}
Acid calcium Water. Calcium
phosphate. metaphosphate.

III. 3Ca(PO_{3})_{2} + 10C = 10CO + Ca_{3}(PO_{4})_{2} = P_{4}
Calcium Carbon. Carbon Basic calcium
metaphosphate. monoxide. phosphate.

If the processes mentioned under II. and III. would pass off in the
practice exactly as there stated, two-thirds, or 13.3 per cent., of
the total quantity of phosphorus contained in the basic calcium
phosphate originally present would be obtained. However, besides these
processes, others take place which cause a loss of phosphorus. By the
action of the red heat upon the acid calcium phosphate, reciprocal
action takes place between the latter, the water and carbon, so that
a portion of the water is decomposed, and in addition to carbon
monoxide, phosphoretted hydrogen is formed; the phosphorus contained
in the latter must be considered as lost. Furthermore, a portion of
the phosphorus is lost in the form of vapor, even with the use of the
best condensing contrivances. In consequence of these losses the actual
yield of phosphorus is between 8 and 11 per cent.

The formation of acid calcium phosphate may be effected either cold or
with the assistance of heat, less time being required in the latter
case. The process without the assistance of heat is as follows:

The bone-ash is brought into a lead-lined wooden tank, and enough
boiling water to cover it poured in. It is then thoroughly mixed with
the water by vigorous stirring with wooden rakes, and the necessary
quantity of sulphuric acid is then run in with constant stirring. When
an intimate mixture has been effected, the tank is covered with a
well-fitting lid and allowed to stand for a few hours. As heat has been
liberated by the introduction of the sulphuric acid into the mixture
prepared with hot water, the entire mass acquires a high temperature.

Decomposition is accelerated by stirring the contents of the tank every
six hours, and the process may be supposed to be finished in 48 hours.
With the use of fresh burnt ash no special phenomena are observed, but
if the ash has been prepared for some time the caustic lime formed in
burning the bones has been completely converted into carbonate of lime,
and the carbonic acid escapes, causing a slight foaming of the mass.
In addition to carbonic acid, there also escapes a certain quantity
of hydrogen fluoride gas, which is liberated by the decomposition of
the calcium fluoride present in the ash. This gas being, even in very
small quantities, very injurious to health, the tanks should be placed
in a thoroughly ventilated room.

When decomposition is complete, enough water is admitted for the mass
to acquire by stirring a thick milky appearance, when it is allowed to
rest until it clarifies and a perfectly clear solution of acid calcium
phosphate stands over the precipitate of gypsum. The clear solution is
drawn off, and the sediment washed with water to obtain the solution
retained by it. For this purpose the gypsum is stirred up with water,
and the thick fluid discharged into a filtering tank. Upon the bottom
of the latter is a four-inch-deep layer of coarse quartz sand; upon
this is placed a false bottom, and upon the latter is spread a linen
cloth. The liquor first running off being milky is poured back into the
tank. However, it runs off clear so soon as the pores of the filtering
cloth have become somewhat contracted by the gypsum.

As a rule, the contents of several filtering vats are run into a common
filter, and the mass is repeatedly allowed to drain off. The dilute
solutions thus obtained are evaporated with the first liquor. A third
lixiviation of the sediment yields a fluid which is used instead of
water in a subsequent operation.

The residue of gypsum is taken from the filtering tanks, and may be
used as a fertilizer.

In the warm way the decomposition of the bone-ash is effected by
providing the decomposing tanks with lead pipes through which steam is
introduced, decomposition being complete in 24 hours, and the first run
of solution of acid calcium phosphate reaches the evaporating pan in a
very hot state. The lixiviation of the gypsum residue is also effected
with water heated by steam, the object of separating the acid calcium
phosphate as much as possible from the gypsum being thus obtained
more completely with a comparatively small quantity of water than is
possible by washing with cold water.

A suitable apparatus for hot lixiviation is shown in Figs. 51 and 52 in
cross section and profile. A lead-lined tank, 13 to 16 feet in diameter
and 3½ feet deep, is fitted with a stirrer furnished with two or four
paddles, and closed by a well-fitting lid. The stirrer is kept in
motion during the entire operation.

[Illustration: FIG. 51.]

[Illustration: FIG. 52.]

A lead steam pipe _D_ furnished with several narrow flat outlet
pipes placed in the direction in which the stirrer revolves, lies
about 4 inches above the bottom of the tank. _W_ is the pipe for the
admission of water, _S_ the lead pipe connected with the sulphuric
acid reservoir, and _A_ an outlet of boards for carrying off the vapor
evolved from the mass in admitting the sulphuric acid. _R_ is a wooden
hopper, which serves for the introduction of the bone-ash, and is
removed when the tank has been filled, the aperture being closed with
a well-fitting wooden lid. The bottom of the tank is furnished with a
lead discharge-cock.

Water is run into the tank, the bone-ash being simultaneously
introduced through the hopper _R_, and the stirrer allowed to revolve
slowly to effect an intimate mixture. Sulphuric acid and steam are then
at the same time admitted. The steam heats the fluid very quickly to
the boiling-point, and assists the action of the stirrer, it passing
out from the outlet pipes in the same direction in which the stirrer
revolves.

When the required quantity of sulphuric acid has been introduced,
the admission of steam is interrupted, the stirrer, however, being
constantly kept in motion. To keep the mass hot, steam is for a few
minutes admitted every hour. When the sulphuric acid has acted for 24
hours, decomposition is complete, and the liquor is discharged through
the cock on the bottom of the tank.

For the evaporation of the liquor leaden pans are used, and this
operation is continued until the fluid has attained a specific gravity
of 1.45. The pans rest upon cast-iron plates covered with a layer of
clay or sand, to prevent them from being injured by the fire gases. For
heating the pans, the fire gases escaping from the distilling furnace
or the bone kiln are utilized.

The fluid having been evaporated to the above-mentioned specific
gravity is now mixed with charcoal powder, or rather granulated
charcoal of the size of small peas, in the proportion of 20 to 25 parts
of charcoal to 100 of liquor. The mixture is then quickly dried in
shallow cast-iron pans heated by a direct fire. Much sulphurous acid is
evolved during this operation, and provision must be made for carrying
off the vapors arising from the pans.

When the mass has been dehydrated so far that it balls together, it
is taken from the pan by means of shovels and brought into a copper
cylinder which is furnished with a sheet-iron sieve-like bottom through
which it is forced into another pan. In this second pan the mass is
moderately heated until a sample of it still evolves slight vapors
and when pressed with the hand, after cooling somewhat, appears still
moist without, however, being sticky. The material is now ready for
distilling and 100 parts of concentrated solution of 1.45 specific
gravity and 20 to 25 parts of charcoal yield about 77 parts by weight
of so-called distilling mass.

It is best to bring the hot mass as taken from the pan at once into
the retorts, as it is very hygroscopic and, if allowed to lie exposed
to the air, would absorb moisture and require to be again dried. If it
cannot be immediately subjected to distillation, it is advisable to
keep it in sheet-metal boxes tightly closed.

The liquor obtained in treating bones for the manufacture of glue with
hydrochloric acid may, as mentioned in Chapter V, be advantageously
utilized in the manufacture of phosphorus. In order to obtain in
crystallized form the acid calcium phosphate contained in it, the
liquor has to be concentrated by evaporation and as during this
operation hydrochloric acid vapors constantly escape, provision must be
made for their removal from the workroom. The operation is conducted
as follows: The flue of the furnace for distilling the phosphorus,
through which the fire gases usually escape to the chimney, is made to
communicate with a long low chamber, which can be tightly closed and
connects at the other end with a high chimney. The flue is fitted with
a slide and by opening the latter, the fire gases are forced to pass
through the chamber before reaching the chimney.

In the chamber are placed large, well-glazed, earthenware vessels which
contain the liquor to be evaporated, the vapors evolved being carried
off by the fire-gases through the chimney. Evaporation proceeds quite
rapidly, and fresh liquor is from time to time introduced through an
earthenware pipe, the operation being repeated until a sample taken
from the full vessels shows on cooling the presence of an abundance of
crystals of acid calcium phosphate.

The admission of the fire-gases into the chamber is then interrupted,
and the contents of the vessels are brought into a wooden tank
furnished with a stirrer, which is kept in constant motion so that
when the liquor cools, only small crystals will be formed. When
crystallization is complete, the mother-liquor is drawn off and again
evaporated. By this operation more crystals of acid calcium phosphate
are obtained, which are, however, less pure than those from the first
liquor. The mother-liquor drawn off from this second yield of crystals
might, on being again evaporated, give more crystals which, however,
would be too impure to be used to advantage.

To obtain the calcium phosphate contained in the last mother-liquor,
the latter is exactly neutralized with burnt lime, a white precipitate
of basic calcium phosphate being thereby obtained. The precipitate is
repeatedly washed in water and allowed to settle, and added in small
portions to the acid liquors obtained by extracting the bones. As these
liquors always contain a considerable quantity of hydrochloric acid in
excess, the basic calcium phosphate, being in a finely divided state,
is readily and completely dissolved.

The crystals of acid calcium phosphate are removed from the
crystallizing tanks by means of wooden shovels and brought into baskets
covered inside with stout sack-cloth. They are left in the baskets
until no more mother-liquor drains off, when the cloths are folded
together and the crystals further freed from liquor by pressure. They
are then heated, with constant stirring, in shallow stoneware pans
until they are so dry as to crumble of their own accord. In this manner
small crystals of a mother-of-pearl lustre are obtained, which feel
like sharp quartz sand and consist of pure acid calcium phosphate.

This mass is mixed with 25 per cent. of its weight of granulated
charcoal. The mixture is heated until it is pulverulent, and then
treated in the same manner as the distilling mass from bone-ash.

In place of stoneware vessels, shallow lead pans may be used for
evaporating the liquor containing calcium phosphate. To prevent the
melting of the lead the pans are bricked in under a very flat arch, so
that the fire gases are forced to pass close over the liquor, the pans
being kept constantly full. When crystallization is complete the liquor
is drawn off and the pans are refilled.

In the manufacture of phosphorus there is left after every distillation
a residue of basic calcium phosphate, and it is advisable to decompose
it with hydrochloric acid, this being effected in a vat lined with lead
or coated with paraffine. The mass is completely dissolved, and the
black sludge remaining on the bottom of the vat consists of charcoal,
which had been added to the distilling mass.

_Distillation of the Phosphorus._—The distilling mass consists of
acid calcium phosphate, charcoal and about 4 to 6 per cent. water. By
heating in the retorts, the acid calcium phosphate is first converted
into calcium metaphosphate, water being eliminated, according to the
following equation:

CaH_{4}(PO_{4})_{2} = Ca(PO_{3})_{2} + 2H_{2}O.

By further heating to a white heat the calcium metaphosphate is so far
reduced as to yield two-thirds of its content of phosphorus, while
one-third remains behind as calcium phosphate, corresponding to the
following equation:

3Ca(PO_{3})_{2} + 10C = Ca_{3}(PO_{4})_{2} + 10CO + 4P.

The mixture of acid calcium phosphate and charcoal is distilled in
glazed fire-clay retorts, 12 to 18 of them being placed on each side of
a so-called galley-furnace. The bodies of the retorts are placed on the
side of the fire, while the necks pass through openings in the walls
of the furnace, those portions of the wall being only lightly bricked
up, as the retorts, after distillation is finished and the furnace
cooled, have to be removed in order to clear out the residue and
introduce fresh mixture. Between each pair of retorts is left a space
of 5 to 6 inches for the passage of the flames.

[Illustration: FIG. 53.]

Experience, however, has proved the advisability of modifying the
galley-furnace by reducing its length and increasing its height, and
placing the retorts in two or three rows, one above the other. Two
such furnaces are placed together with their narrow sides, so that the
fire-gases of both meet in a common chamber, and are conducted from
the latter under the evaporating pans. Four such furnaces may also be
arranged in the form of a cross, and their fire-gases conducted into a
common chamber. By arranging the furnace, as is most frequently done,
for three double rows of seven retorts each, it will hold 42 retorts, a
double furnace 84, and one in the form of a cross 168. The arrangement
of a double furnace is shown in Fig. 53.

The wall _C_, which separates the two fire-places, serves for
supporting the lowest row of retorts, while the second and third rows
rest upon intermediate pieces. The fire gases pass through flues into
the space over the furnace, the top of which may be directly formed
by the evaporating pans. It is, however, more suitable to place the
evaporating pans on one side and not run the collecting chamber for
the fire gases directly into the chimney. For the introduction of the
retorts into, and their removal from, the furnace, a narrow door is
provided between each two vertical rows of retorts. After placing the
retorts in the furnace, this door is closed with stones and the joints
luted with clay.

Every three retorts lying one above the other have a common receiver,
_p_, for the collection of the phosphorus distilled off. The necks,
_r_, of the retorts terminate in the collecting pipe, _o_.

The galley-furnaces, previously described, require the use of a fuel
which yields a very long flame, and can, therefore, be heated only with
wood or very fat coal.

In order to render possible the use as fuel of coal yielding a short
flame, and especially of coke, furnaces have been constructed which
hold only a small number of retorts, generally five, placed in two
rows, by twos and threes, one above the other. The retorts are
cylindrical in form, and have a capacity equal to that of several
smaller retorts.

The _receivers_ for collecting the phosphorus distilling over from the
retorts are made of clay, and should be well glazed and smooth inside.
Each receiver consists of two parts, one of which is a cylindrical
vessel open at the top, into which the other part fits, and is fixed
by means of a rim, which is prolonged so as to form a neck, between
which and the first part is inserted a tube fitted on the neck of the
retort, while the other end of this tube dips for about 4 inches into
the receiver, the latter being filled with water.

Under certain conditions enameled cast-iron may be used as a material
for receivers, but the enamel must be of such a nature as not to be
attacked by the phosphorus vapors, otherwise the receivers would in a
short time be destroyed.

The retorts having been filled with the required quantity of mixture
are placed in the furnace and the brickwork is restored. The fire is
then kindled and kept up very gently for some time in order to dry
the fire clay used in joining the bricks. The receivers are filled
with water and fitted to the retorts. In each receiver a small iron
spoon is placed fastened to iron wire which serves as a stem. After
six to eight hours of firing the heat has been so much increased as to
cause the expulsion of any moisture left in the material placed in the
retorts, while quantities of hydrocarbon gases and oxide of carbon are
formed and expelled with the sulphurous acid. Subsequently other gases
are given off, and because they contain some hydrogen phosphide are
spontaneously inflammable. As soon as this phenomenon is observed the
joints of the receivers and apparatus connecting it with the retorts
are luted with clay, care being taken to leave, by the insertion of
an iron wire, a small opening for the escape of the gases, which are
as speedily as possible removed by well arranged ventilators from the
building in which the furnace is placed. The appearance of amorphous
phosphorus at the small opening indicates the commencement of the
distillation.

The spoon is then placed in the receiver in such a direction that any
phosphorus coming over may collect in it. During the progress of the
operation, and as long as any phosphorus distils over, the evolution
of combustible gases continues, and consequently a small blue-colored
flame is observed at the opening in the lute. The water in the
receiver is kept cool during the operation. After forty-six hours,
with greatly-increased firing, a full white heat is reached, and the
quantity of phosphorus coming over has decreased so much as to make
a continuation of the ignition process wasteful. The receivers are
therefore disconnected from the retorts.

The receivers are taken to a special room and entirely submerged
in large wooden troughs filled with water in order to drive off
inflammable gases still contained in them and to cover the phosphorus
with water. They should be opened only after this has been done, and
every manufacturer should rigidly enforce the rule of carrying on the
operation in the above-described manner. Crude phosphorus is very
inflammable, and when carelessly handled by the workmen may inflict
horrible burns and, as the phosphorus as a rule causes blood-poisoning,
such injuries generally cause death.

The phosphorus is then removed from the receivers (always under water).
The trough in which this operation is effected should be provided, a
few inches above the actual bottom, with a perforated false bottom upon
which the receivers are placed. The larger pieces of phosphorus taken
from the receivers are collected, under water, in special vessels,
while the smaller pieces fall through the perforations of the false
bottom to the actual bottom. When all the receivers have been emptied,
the water in the trough is discharged into a large barrel in which it
remains until the particles of phosphorus have subsided. The water is
then drawn off, with the exception of a sufficient quantity to cover
the phosphorus in the barrel.

The water from the receivers as well as from the troughs shows a quite
strong acid reaction due to phosphoric acid, which has been formed by
the combustion of phosphorus and passed into solution. In order not
to lose this phosphoric acid, the water is partly used for filling
the receivers and partly for mixing the bone-ash before adding the
sulphuric acid.

Crude phosphorus is a mixture of crystalline (ordinary) phosphorus with
amorphous phosphorus, the reddish color of the mass being due to the
latter. It further contains phosphorus in various stages of oxidation,
free carbon, and if impure sulphuric acid has been used, arsenic in
combination with phosphorus.

_Refining and purifying the phosphorus._ The crude phosphorus was
formerly purified by forcing it through the pores of stout wash leather
by means of a machine. The crude phosphorus contained in a tightly
tied piece of wash leather is placed on a perforated copper support
situated in a vessel filled with water at 122° to 140° F. As soon as
the phosphorus is molten, there is placed on the wash leather a wooden
plate which by the aid of a mechanical arrangement and a lever can be
forced downwards so as to cause the fluid phosphorus to pass through
the pores of the leather, the impurities being retained. The phosphorus
in the form of a slightly yellowish fluid collects on the bottom of
the vessel and is immediately moulded into the shape in which it is
brought into commerce. The residue in the wash leather consists chiefly
of charcoal dust and amorphous phosphorus. The wash leather can, as a
rule, be only used once, and only small quantities of phosphorus can be
worked at one time.

A more suitable process of purification is as follows: Porous, unglazed
porcelain or earthenware plates are fixed in an iron cylinder connected
with a steam boiler. The cylinder having been hermetically closed is
placed in a vessel containing water at 140° F. When the phosphorus
is molten, steam of a few atmospheres’ pressure is admitted into the
cylinder, the phosphorus being thus forced through the earthenware
plates.

The phosphorus obtained by either of these methods is free from
mechanically admixed particles of charcoal and amorphous phosphorus,
but it is by no means pure, as all the substances dissolved in it
(oxides of phosphorus) pass through the filter. The loss of phosphorus
amounts to from 5 to 6 per cent. of the weight of the crude product.
The masses taken from the filter plates are therefore collected
and subjected by themselves to distillation in order to obtain the
phosphorus contained in them.

To obtain pure phosphorus, the crude product has to be subjected to
distillation, this operation being carried on in iron retorts of a
peculiar make, and shaped like the glass retorts used in chemical
laboratories. The necks of these retorts dip to a depth of ½ to ¾ inch
in water contained in a basin filled to the rim so that any phosphorus
which is discharged into this water causes it to overflow. The crude
phosphorus having been fused under water is next mixed with 12 to 15
per cent. of its weight of moist sand, and this mixture placed in
the retorts, the object of the mixing with sand being to prevent the
phosphorus becoming ignited during the filling of the retorts.

[Illustration: FIG. 54.]

Fig. 54 shows a distilling apparatus. In consists of a cast-iron
retort, _K_, fitted with a cast-iron dome, _H_, the joint being made
tight by means of clay and screws. The dome, _A_, tapers to a cone and
terminates in a wide glass tube, _R_, bent at a right angle, and having
at the mouth a diameter of about 2⅓ inches.

This dome, _A_, dips ¾ inch deep in water contained in the copper
gutter of the receiver filled to the brim. The copper receiver, _P_,
stands in water. It contracts below in the form of a funnel, and
terminates in a pipe closed by a cock, _G_, to which is fitted a glass
tube bent at a right angle.

The retort having been filled with the mixture of crude phosphorus and
sand, the dome, _H_, is placed in position and the apparatus brought
into the furnace. The dome is then connected with the condensing
apparatus.

The fire is so regulated that the retort is uniformly heated from all
sides in order to evaporate as quickly as possible the water still
adhering to the phosphorus mixture, since at a higher temperature the
water acts upon the phosphorus, and phosphoretted hydrogen is formed.
It being scarcely possible to entirely avoid the formation of the
latter, the receiver has been given the above-described form, so that
the disagreeable vapors formed by the ignition of the phosphoretted
hydrogen cannot escape into the workroom. The gas escapes through the
conical dome. _A_, and the glass pipe, _R_, into the open air, where it
burns without molesting the workmen.

At first steam only escapes from the retort, while later on
phosphoretted hydrogen passes off. The evolution of the latter,
however, soon ceases almost entirely, and the phosphorus distils
uniformly over. Heating is continued until the retort shows a slight
red heat, all the phosphorus having by that time passed over. The
residue in the retort consists only of sand and charcoal.

The phosphorus passing over in the various stages of distillation shows
different qualities. The portion which passes over first is perfectly
pure, and when cold presents the appearance of bleached wax; the
portions passing over later on are of a yellowish-red color, while the
last portions are colored brick-red by amorphous phosphorus, and have
to be collected by themselves. They are again brought into the retort
in the subsequent operation.

In order to be able to separate the phosphorus passing over according
to quality, the receiver for the melted mass is fitted with a conical
bottom furnished with a glass tube which can be closed by the cock _G_.
This glass pipe leads to a tank filled with warm water, in which the
collecting vessel is immersed. The phosphorus collecting in this vessel
is from time to time allowed to run into a vessel filled with water,
another vessel being substituted when the phosphorus commences to show
a yellowish color.

_Moulding the refined phosphorus._ It has long been the custom to
mould phosphorus into the shape of sticks formed by the aid of a glass
tube open at both ends, one of these being placed in molten phosphorus
covered by a stratum of warm water. The liquid phosphorus is sucked by
the operator into the tube until it is quite filled. The lower opening
of the tube being kept under water is closed by the finger of the
operator; the tube is instantly transferred to a vessel filled with
very cold water by which the phosphorus is solidified. It is removed
from the glass tube by pushing it out with a glass rod or iron wire
while being held under water.

Independent of its danger, the method of moulding above described
is not suitable for the manufacture on a large scale, and various
contrivances have been introduced for this purpose; the apparatus
constructed by Seubert being much used. It consists of a copper boiler
fitted on a furnace. To the flat bottom of this boiler is fitted by
hard solder an open copper trough communicating with a water-tank. In
the boiler is fitted a copper funnel provided with a horizontal tube.
This portion of the apparatus is intended for the reception of the
phosphorus. At the end of the horizontal tube is placed a stopcock,
while the portion of the projecting mouth of the tube beyond the
cock is widened out and fitted by means of bolts and nuts, with a
flange-like copper plate, into which are inserted two glass tubes.
Into the copper trough is let a wooden partition, which serves the
purpose of supporting the glass tubes as well as of preventing the
communication of the hot water in the boiler and a portion of the
trough with the cold water of the tank and the portion of the trough
nearest to it. The phosphorus having been introduced in the boiler, the
water is gently warmed so as to cause the fusion of the phosphorus.
As the warm water reaches to the wooden partition, it is evident that
on opening and closing the cock at the end of the horizontal tube,
some phosphorus will pass through and flow out of the glass tubes, but
that remaining in these tubes will solidify, and on opening again the
cock at the end of the horizontal tube, the solid sticks of phosphorus
may be removed from the glass tubes by taking hold of the piece of
projecting phosphorus, the phosphorus being immediately immersed under
water in the tank, and kept there protected from the action of the
light.

Notwithstanding its apparently very practical arrangement, Seubert’s
apparatus possesses many disadvantages, the principal drawback to its
use being that the phosphorus-sticks frequently stick so firmly in the
glass tubes that the operation of moulding has to be interrupted, the
tubes removed, and the phosphorus stick pushed out with a stout wire.
Furthermore, the melted phosphorus in flowing in frequently causes the
glass tubes to crack.

Hence many factories have returned to the old method of moulding by
sucking the fused phosphorus into glass tubes. To render this operation
perfectly free from danger, the apparatus shown in Fig. 55 has been
devised, by means of which a larger quantity of phosphorus can in a
short time be moulded into sticks.

A hollow prism, _P_, of stout sheet-iron is fitted at its lower end
with 8 to 12 short tubes. In the latter are inserted air-tight, by
means of rubber, 12 glass tubes, _G_, each about 3¼ feet long and
somewhat contracted at the lower end. Two iron rods, _E_, are fitted
to the prism and, by means of suitably-shaped pieces of cork, serve
to hold the glass tubes in their proper position. To the back of the
prism is secured a rubber tube, _L_, which communicates with a small
air-pump, and to the upper surface of the prism is fixed a handle.

[Illustration: FIG. 55.]

The phosphorus to be moulded is fused in a shallow vessel of such a
shape that a portion of it is covered only about 2 inches deep with
water. The glass tubes are placed in the fused phosphorus and the air
is sucked from them by means of the air-pump; the external air-pressure
forcing the fused phosphorus into the glass tube.

The tubes are now sufficiently raised to allow of a rubber plate being
pushed under their mouths in the shallower portion of the vessel. The
rubber plate is pressed against the tubes and the entire apparatus
placed in a vessel filled with cold water. The phosphorus solidifies
very rapidly in the lower narrower portions of the tubes, and the
latter are immediately detached from the prism and replaced by others.
The phosphorus when entirely cold is pushed from the glass tubes by
means of a wire or wooden stick.

In some factories the phosphorus is moulded in wedge-shaped sheet-metal
boxes. In packing two such wedges are laid together with their
longitudinal sides so as to form a prism.

Phosphorus is stored either in strong sheet-iron tanks or in wooden
boxes lined with tinned sheet-iron and covered with a stratum of water
fully 1¼ inches deep. For shipping smaller quantities of phosphorus,
the sticks are packed in tinned sheet-iron boxes and the latter having
been filled up with water, the lid is soldered on. To prevent the water
from freezing in winter, it is advisable to mix it with spirits of wine.

_Manufacture of phosphorus with the assistance of electricity._ Readman
and Parker have recently devised a process for the manufacture of
phosphorus on a large scale in a continuously working apparatus by
means of a powerful electric current, such as is yielded by a larger
dynamo. The mixture used for the operation differs from the ordinary
one of calcium phosphate and charcoal, in that it contains in addition
a slag-forming body—a flux—silicic acid (quartz sand) being at first
used for the purpose. Numerous experiments, however, have shown kaolin
or pipe clay, _i. e._, aluminium silicate, to be more suitable.

When a mixture of calcium phosphate, charcoal and aluminium silicate
is exposed to the action of the voltaic arc the following process
takes place: By the extraordinarily high temperature prevailing in the
proximity of the arc, the reduction to phosphorus of the phosphoric
acid contained in the calcium phosphate is very rapidly effected. The
liberated calcium combines immediately with the aluminium silicate to
a calcium-aluminium-silicate, _i. e._, to a glass fusible with the
greatest difficulty which, however, at the high temperature possessed
by the voltaic arc becomes fluid like water.

The apparatus employed is, generally speaking, similar to the electric
furnaces now in use. The mass to be treated is contained in a carbon
crucible in which the two electrodes are placed opposite to one
another, so that the electric current must pass through the mass.
However, since the phosphorus at the moment of liberation would, on
coming in contact with oxygen, immediately burn again to phosphorus
pentoxide, the apparatus has to be so arranged that the entire process
passes off in an entirely indifferent gas, and the condensation of the
phosphorus vapors takes place under the same conditions.

Fig. 56 shows the apparatus employed for the electrolytic manufacture
of phosphorus.

[Illustration: FIG. 56.]

The carbon crucible, _a_, is enclosed by a clay jacket, which serves as
an insulator of heat, and is closed by a graphite cover, _c_. Through
the bottom and the cover of the crucible pass the two electrodes, _k
k_, which conduct the current, and between which the voltaic arc is
formed. To prevent the upper electrode from becoming too highly heated
during the operation, it is constantly cooled by water admitted at _g_,
and running off at _f_. Through the pipes _h_ and _l_ an indifferent
gas—as a rule, illuminating gas—is conducted into the apparatus and
escapes together with the phosphorus vapors through the pipe _d_.

In operating with the apparatus, the reduction soon takes place, and
the phosphorus vapors escape through _d_, while a thinly-fluid slag
remains behind in the crucible. The slag is discharged through a pipe
not shown in the illustration, and a fresh charge of the mixture
brought into the crucible _a_, the process of reduction being thus
carried on without interruption. The phosphorus vapors escaping from
_d_ are conducted through a cooled pipe and condense to a liquid in
water heated to between 122° and 140° F. contained in a receiver.

Although the electrolytic method of manufacturing phosphorus is of
quite recent origin, a considerable portion of the phosphorus brought
into commerce is now prepared in that manner, it being cheaper than the
older processes which involve a very large consumption of fuel.

CHAPTER VII.

METHODS OF BLEACHING GLUE.

Many experiments have been made to bleach glue, _i. e._, to obtain
masses as colorless as possible, or at least slightly colored, the
resulting product being more valuable than the dark-colored one.

a. _Bleaching in the Air._

The principal requisite for obtaining a beautiful bleached glue is that
the unbleached product is clear, _i. e._, transparent, even if of a
dark color, this being the best criterion of well-made glue.

Glue may be bleached whilst being prepared, or the finished cakes may
be subjected to the bleaching process.

For the purpose of obtaining pale-colored glue from skin or cartilage
it is advisable to expose the materials in thin layers to the direct
action of the sun. Moist oxygen when acted upon by the sun is converted
into ozone, which exerts an extraordinary bleaching effect upon organic
substances.

b. _Bleaching with Chlorine._

The powerful bleaching effect of a solution of chlorine in water upon
organic matter is well known; the water is decomposed, and bleaching is
effected by the oxygen which is liberated. Hence skin and cartilage may
also be bleached by placing them in a vessel filled with weak solution
of chlorine in water and leaving them in contact with it until the
fluid shows no longer an odor of chlorine. When bleaching is finished
the materials are suspended in a certain quantity of hydrochloric acid,
which has finally to be removed by repeated treatment with water.

c. _Bleaching with Animal Charcoal._

Animal charcoal is distinguished by its great power of absorbing
coloring as well as odoriferous matter, and may also be used for
discoloring glue-liquors. This may be done by allowing the thin liquor,
as it comes from the glue-boiler, to run through a filter filled with
animal charcoal, or with the use of charcoal dust.

In the latter case the glue-liquor is collected in a clarifying vessel
and a quantity of charcoal dust amounting to about 3 to 4 per cent. of
the weight of the glue in the liquor stirred in. The finely divided
charcoal sinks slowly down, carrying with it the solid particles
suspended in the liquor, and collects on the bottom of the clarifying
vessel in the form of a black slime.

In order to discolor the glue-liquor as much as possible, when working
on a large scale, it is recommended to use a number of cylinders filled
with animal charcoal. These cylinders are connected one with the other
in such a manner that the glue-liquor runs into the first cylinder from
the top, passes out from the lower end of this cylinder through a pipe
into the second cylinder, traverses this from bottom to top, passes
into the third cylinder from the top, and so on. The animal charcoal
in the first cylinder loses its discoloring power first. The cylinder
is then disengaged, freshly charged and placed last in the series of
filters, the process being the same with the second cylinder, and so
on, so that after a certain time all the cylinders have alternately
occupied the first and last places in the series of filters.

By the use of animal charcoal it is even possible to render very dark
and badly-smelling glue, entirely colorless and free from odor. The
darker the glue is, the longer it must, of course, be subjected to the
action of the animal charcoal.

d. _Bleaching with Sulphurous Acid._

Bleaching of the glue-liquor itself by means of sulphurous acid is
best effected in the clarifying vat. For this purpose, the latter is
fitted with a lead pipe reaching to the bottom and terminating in a
perforated coil. Through this pipe gaseous sulphurous acid, generated
in a suitable sulphur-burner is forced through the liquor by means of a
force-pump.

The sulphurous acid is dissolved in the glue-liquor, the latter being
thereby bleached. When the liquor has acquired a much paler color and
a strong odor of sulphurous acid is perceptible in the air over the
vat, the introduction of gaseous sulphurous acid is interrupted and the
liquor allowed quietly to clarify, the acid dissolved in it exerting
during this time a further bleaching effect. By this means ordinary
brown joiners’ glue of good quality may be converted into a pale-yellow
product similar to the variety known as gilder’s glue.

[Illustration: FIG. 57.]

For bleaching finished glue, solution of sulphurous acid in water may
be used, the apparatus shown in Figs. 57 and 58 being suitable for the
purpose.

The apparatus for the production of the acid solution consists of the
sulphur-burner _O_, the wash-vessel for the gas _W_, and the vessel _T_
for dissolving the gas in water.

The sulphur-burner _O_ is a small brick vault of sufficient size to
hold a vessel _S_ having a capacity of a few quarts. In front the
sulphur-burner is provided with a well-fitting door _J_, which is
furnished with a small aperture for the introduction of an iron pipe
into the burner. The lead-pipe _R_ leads from _O_ to the bottom of the
wash-vessel _W_, and from the lid of the latter rises a pipe _R_{1}_,
and runs along the bottom of the trough filled with water. This trough
is provided with a wooden lid and the cock _H_, and by means of the
latter the fluid can be discharged into the vessel _G_.

[Illustration: FIG. 58.]

The trough _T_ is filled with water and _W_ is also filled
three-quarters full. In the burner _O_ is placed a dish _S_ filled with
sulphur, and the latter ignited. The door is then closed and air blown
in through _A_ by means of a bellows, the joints of the door _J_ being
at the same time luted with clay.

In contact with air, the sulphur burns to sulphur dioxide. The latter
is freed in the wash-vessel from sulphur vapor which has been carried
along, and passes from _R_{1}_ through the numerous perforations into
the water in _T_ where it is dissolved to sulphurous acid.

Saturation with sulphurous acid of the fluid in the trough is complete
when the suffocating odor of the acid is perceptible in the proximity
of _T_. The fluid is then discharged, replaced by water, which is again
saturated with sulphuric acid, and so on.

The cakes of glue to be bleached are placed in a trough (Fig. 58), in
which are arranged several frames, _B_, covered with linen. The cakes
of glue are placed upon these frames and the trough is filled with
sulphurous acid so that it stands a few inches deep over the uppermost
frame. The cakes of glue swell up rapidly in the solution of sulphurous
acid, and yielding up their salts become bleached. After twelve hours
the fluid is discharged through the cock, _H_, and if glue of a
particularly fine appearance is to be produced the cakes are treated
twice more with solution of sulphurous acid.

When bleaching is finished the trough is filled with clean water, in
which the glue is allowed to remain for a few hours, when the frames
are lifted out and the cakes dried.

By this method glue may be bleached to such an extent as to render it
fit as a substitute for gelatine for many purposes, for instance, for
the imitation of thin plates of ivory.

Dr. Bruno Terne’s apparatus (Fig. 40), previously described, may also
be used for the generation of sulphurous acid for bleaching purposes.

CHAPTER VIII.

DIFFERENT VARIETIES OF GLUE AND THEIR PREPARATION.

Besides the broadly-distinguished forms of skin-and bone-glue, the
trade recognizes a large number of varieties, distinguished either by
their value or their fitness for special purposes.

_Joiner’s Glue._—This variety is without doubt the oldest in use and
most in demand, and its principal requisite is its great adhesive
power. It is used for joining wood, leather, paper, etc., and varies
very much in quality and price.

The best variety is prepared from scraps of hide and skin. A light
color not being especially demanded, there existing rather a prejudice
in favor of a dark-colored article, waste of cattle and horse skins and
tendons can be used for its manufacture.

Joiner’s glue, which is generally preferred in thin cakes, is chiefly
manufactured in regular glue factories, though to be able to compete
with the bone-glue turned out by the large establishments, the
glue-boiler generally mixes skin and bone-glue, and is thus enabled to
turn out a tolerably good quality. The price paid for the different
varieties of joiner’s glue varies very much, being generally higher in
winter than in summer, and is frequently more regulated by the external
appearance of the article than by its actual value. Glue without gloss,
very much warped and of a very dark color, may, notwithstanding its
faulty appearance, possess excellent qualities.

Nothing need be said about the manufacture of joiner’s glue, since what
has been said about the manufacture of glue in general suffices for the
purpose.

_How to make and use glue._ Break the glue into small pieces, put it
into an iron kettle, cover it with water, and allow it to soak twelve
hours; after soaking boil until done. Then pour into a box which can be
covered air-tight; leave the cover off until cold, then cover up tight.
As glue is required, cut out a portion and melt in the usual way.
Expose no more of the made glue to the atmosphere for any length of
time than is necessary, as the atmosphere is very destructive to made
glue.

All glue, as received from the factory, requires the addition of water
before it will melt properly, and every addition of water (while
the glue is fresh made) will, up to a certain point, increase its
adhesiveness and elasticity. Some glues will bear more water than
others, but all will bear more water than usually falls to their share,
and that, too, with a greater improvement in the quality of the work.
For glue to be properly effective, it requires to penetrate the pores
of the wood, and the more a body of glue penetrates the wood the more
substantial the joint will remain. Glues that take the longest to dry
are to be preferred to those that dry quickly, the slow-drying glues
being always the strongest, other things being equal. Never heat made
glue in a pot that is subjected to the direct heat of the fire or a
lamp. All such methods of heating glue cannot be condemned in terms too
strong. Do not use thick glue for joints or veneering. In all cases
work it well into the wood in a manner similar to what painters do
with paint. Glue both surfaces of your work excepting in the case of
veneering. Never glue upon hot wood, as it will absorb all the water in
the glue too suddenly, and leave only a very little residue, with no
adhesiveness in it whatever.

_Holding power of glue._ 1. Glue exerts a far greater hold on surfaces
of wood cut across the grain than on those that have been split, or cut
with the grain.

2. When two surfaces of split wood are laid together, the hold of the
glue is the same whether the fibres are laid parallel or crosswise to
each other.

3. The holding power of glue on different woods estimated in
kilogrammes per square centimeter (0.155 square inch) is as follows:

Cut across the grain. Split.
Beech, 155.55 (342.21 lbs.) 78.83 (173.42 lbs.)
Hornbeam, 126.50 (278.30 lbs.) 79.16 (174.15 lbs.)
Maple, 87.66 (192.85 lbs.) 63.00 (138.6 lbs.)
Oak, 128.34 (282.34 lbs.) 55.16 (121.35 lbs.)
Fir, 110.50 (243.10 lbs.) 24.16 (53.15 lbs.)

_Cologne glue._ The variety of glue known under this name is prepared
from selected scraps of hide and skin, and is consequently very pure,
and possesses great adhesive power. It is of a light-brown color,
and comes into commerce in short thick cakes of great hardness. It
is an excellent quality of glue, and is preferred to all others by
bookbinders, workers in leather, etc. There are many imitations of this
variety, bone-glue being frequently sold as Cologne glue.

The genuine article is manufactured from refuse of hide, which, after
liming, is carefully bleached in a bath of chloride of lime, the
concentration of which depends on the darker or lighter color of the
glue-stock. For 220 lbs. of glue-stock, it is generally customary to
use 1 lb. of chloride of lime mixed with sufficient water to cover the
stock.

After thorough impregnation of the glue-stock, which generally requires
about half an hour, add sufficient hydrochloric acid to impart an acid
taste to the bath of chloride of lime. To be able to mix the mass
thoroughly, it is best to use a vat provided with a stirring apparatus.
After allowing the acid to act for a quarter of an hour, remove every
trace of it by careful washing.

To obtain a jelly as clear as possible, the gelatinous liquor is drawn
off as soon as the thin portions of the glue-stock and the outside of
the thicker ones are dissolved, they being more thoroughly bleached
than the rest. The residue is worked into darker glue.

_Russian glue._ This variety is of a dirty white color, and, like
Cologne glue, is brought into commerce in short, thick cakes. Its color
and opaqueness are imparted to it by an addition of 4 to 8 per cent. of
white lead, chalk, zinc white, or permanent white (sulphate of baryta).
It has been claimed that the superior adhesive power of Russian glue
is due to this addition of mineral substances, but the results of many
experiments fail to substantiate this claim. In case the glue turns
out turbid, it may be of advantage to make it opaque by an addition of
coloring matter, but the quality of the glue remains unchanged. The
best time to add the coloring matter is shortly before drawing the
glue-liquor from the clarifying vats into the cooling boxes, as the
jelly is then of sufficient consistency to prevent the substances from
settling on the bottom. Skin-glue, as well as bone-glue, is sold under
the name of Russian glue.

Quite a considerable quantity of Russian glue brought into commerce in
the form of brownish-white sheets is prepared from bones, the latter
being degreased by boiling, steaming or extraction, and the solution of
the mineral constituents effected by means of hydrochloric acid. The
treatment with acid is, however, continued only till the bones commence
to become soft and flexible. The solution of phosphates is then drawn
off, and the softened bones are washed and in the usual manner worked
to glue.

By this incomplete treatment with hydrochloric acid, a certain quantity
of the phosphates remains in the cartilage and is inclosed in the
glue prepared from it, the finished product acquiring thereby a dirty
whitish color, which is by many considered an evidence of its quality.
This mechanical admixture of phosphates, however, does not affect the
adhesive power of the glue, neither increasing or decreasing it. Such
white and opaque glue is manufactured to answer the demand in certain
quarters of the trade, and, as above mentioned, heavy white substances
are often intentionally incorporated with skin glue, as well as bone
glue, to give it the appearance of Russian glue. These heavy powders
add to the weight of the product, though when incorporated with it in
small quantities do not injure its adhesive power, but large quantities
render the product weaker.

_Patent glue._ This term is applied to an indefinite number of
preparations, but particularly refers to a very pure variety of bone
glue of a deep dark-brown color not showing net marks. It is very
glossy, and swells up much in water. To satisfy the demand for thick
cakes, they must be cut from very concentrated jelly to insure their
drying.

_Gilder’s glue_ is found in commerce in very thin, pale yellow cakes
tied up in packages weighing about 2 lbs. each. It is a variety of skin
glue bleached with chloride of lime, and dissolves with difficulty in
water. The first runnings from the boiler are used for its manufacture.

A very superior article of gilder’s glue is obtained by cutting
rabbit skins into fine shreds and boiling in water, then turning the
mixture into a basket through which the liquid passes, leaving the
refuse behind. About 100 grammes (3.52 ozs.) of sulphate of zinc and
20 grammes (0.705 oz.) of alum are then separately dissolved in pure
boiling water and poured into the first-mentioned liquid, and the whole
well stirred together while hot. The mixture is then passed through a
sieve into a rectangular box, in which the jelly remains twenty-four
hours in winter, or forty-eight in summer. The solid mass is taken from
the box, cut into slices of proper thickness, and dried upon nets.

_Size glue and parchment glue_ are manufactured in the same manner.
Both are skin-glues, and can be readily produced by following the
directions given for the manufacture of skin-glue.

_Paris glue_ is used for sizing. It is brown, opaque, and almost always
soft. Being very hygroscopic, and imparting a suitable flexibility to
the felt, it is better adapted for hatter’s use than any other variety.
For its manufacture only the generative organs, or the thick tendons
of the legs of cattle and horses, are used, or other waste and fleshy
parts, and substances mixed with small bones, which, if thoroughly
cleansed, might yield a good quality of glue, but are intentionally
transformed by too long-continued boiling, whereby the gelatinous
solution is largely deprived of its adhesive power, and yields a
hygroscopic product.

_Liquid Glues._ These are chiefly combinations of glue with some
ingredients added to destroy the gelatinizing property and yet not
impair its adhesiveness. They remain for a long time clear and syrupy,
and are used for a variety of purposes. Below are given a few receipts
for such glues.

1. Dissolve 38 parts of glue in small pieces in 100 parts of acetic
acid. Solution is promoted by exposing the vessel to the sun or placing
it in hot water.

2. Dissolve 50 parts of light-colored glue in 50 parts by weight of
hot water, in which 14 parts of fused magnesium chloride have been
dissolved. The solution on cooling does not gelatinize, but remains
syrupy, the density varying according to the quantity of water used. In
the preparation of printing inks it can be used as a substitute for gum.

3. Dilute 10 parts of strong phosphoric acid with an equal weight of
water, and then gradually add 4 parts of ammonium carbonate in the dry
state. When the effervescence has subsided, add a further 5 parts of
water and warm on the water-bath or steam-chest to 158° F. Now add 20
to 40 parts of glue, according to the consistency required, and stir
until all is dissolved. Cool.

4. Dissolve 20 parts of glue in an equal weight of hot water, then
cautiously pour in, stirring constantly, 4 parts of strong nitric
acid, warm until the nitrous fumes have been driven off, filter, if
necessary, through fine shavings, and allow to cool.

5. Dissolve 3 parts of glue in small pieces in 12 to 15 parts of
saccharate of lime. By heating, the glue dissolves rapidly and remains
liquid, when cold, without loss of adhesive power. Any desirable
consistency can be secured by varying the amount of saccharate of lime.
Thick glue retains its muddy color, while a thin solution becomes clear
on standing.

The saccharate of lime is prepared by dissolving 1 part of loaf sugar
in 3 parts of water, and after adding one-fourth part of the weight of
sugar of slaked lime, heating the whole to between 149° and 185° F.,
and allowing it to macerate for several days, shaking it frequently.
The solution, which has the properties of mucilage, is then decanted
from the sediment.

The solution of the glue in saccharate of lime is readily accomplished,
even old gelatine, which has become insoluble in water, dissolving
without difficulty. This variety of liquid glue possesses great
adhesive power, and admits of many uses.

6. Dissolve 8 parts of glue in 16 parts of hot water, then add ½ to 1
part of hydrochloric acid, and 1½ parts of sulphate of zinc. Keep the
mixture for 8 hours at 158° F., then filter through fine shavings, and
allow to cool.

_Steam glue._ Under this name several varieties of liquid glue are
brought into commerce. They are prepared as follows:—

1. _Russian steam-glue._ 100 parts of a good quality of glue, 100 to
110 parts of warm water, and 5.5 to 6 parts of commercial nitric acid
of 36° B.

2. _Pale steam-glue._ 100 parts of glue, 200 of water, and 12 of nitric
acid of 36° B.

3. _Dark steam-glue._ 100 parts of glue, 140 of water, and 16 of nitric
acid of 36° B.

Soak the glue in cold water, then pour the necessary quantity of warm
water over it, and heat gently on a water-bath until all the glue is
dissolved. Next add gradually the nitric acid with constant stirring,
and to the Russian steam-glue 6 parts of finely pulverized sulphate of
lead, which will impart to it the white color.

_Chrome glue._ This preparation is very permanent and durable. To
prepare it add to a moderately concentrated solution of 5 parts of
glue 1 of dissolved acid chromate of lime, this salt being considered
better for the purpose than the bichromate of potash usually used. The
glue thus prepared becomes, after exposure to the light, insoluble
in water in consequence of a partial reduction of the chromic acid.
This preparation can be used for cementing glass articles, liable to
be exposed to boiling water, the treatment being the ordinary one of
applying the glue to both surfaces of the fractured object, and then
binding them together until dry, and exposing them for a sufficient
length of time to the light, after which boiling water will have no
effect upon them. It is suggested that this preparation is better
adapted to cementing the covers on glass slides than any now in use.
The same preparation can be applied for making fabrics water-proof,
especially sails, awnings, etc., where no great flexibility is
required. Two or three applications of the glue, either by immersion
of the object in it, or by the use of the brush, will answer the
purpose. Roofing paper is also rendered impervious, even when exposed
to long-continued rains.

_Glue for attaching leather to metal._ A method of affixing leather to
metal, so that it will split before it can be torn off, consists in
digesting a quantity of nutgalls, reduced to powder, in eight parts of
distilled water for six hours, and filtering it through a cloth; then
dissolving one part by weight of glue in the same quantity of water,
and allowing it to remain twenty-four hours. The leather is moistened
with the decoction of nutgalls and the solution of glue applied to the
metal, previously roughened and heated. The leather is then laid upon
it, and dried under pressure.

_Glue for leather, paper, etc._ The following process affords an
unusually adhesive paste, adapted to fastening leather, paper, etc.,
without the defects of glue, and if preserved from evaporation in
closed bottles will keep for years. Cover 4 parts, by weight, of glue
with 15 parts of cold water, and allow it to soak for several hours;
then warm moderately till the solution is perfectly clear, and dilute
it with 65 parts of boiling water, intimately stirred in. Next prepare
a solution of 30 parts of starch in 200 of cold water, so as to form
a thin homogeneous liquid free from lumps, and pour the boiling glue
solution into it with thorough stirring, and at the same time keeping
the mass boiling.

_Glue for parchment paper in making sausage skins._ The supply
of intestines soon being exhausted by the enormous quantity
of pease-sausages manufactured for the German army during the
Franco-German war, the necessity arose for a substitute. This consisted
of a tube of parchment glued together. Millions of these tubes from Dr.
Jacobsen’s factory were tested by the government, and found to answer
the purpose admirably. They were even boiled for hours without either
the glued seam or the paper itself being injured by the operation.
The secret of the composition of the glue employed for fastening
the parchment paper seems to be well kept, but the one given in the
following is equal to it in all respects, if not indeed identical:
Add to one quart of a good adhesive solution of glue ¾ to 1 oz. of
finely powdered bichromate of potash. Warm the mixture slightly on a
water-bath when about to use it, and before applying it moisten the
parchment paper. The latter, when glued with this preparation, as in
the formation of the small cylinders for sausages, must be rapidly
dried on a hurdle, and then exposed to the light until the yellow glue
becomes brownish. The cylinders are then slowly boiled in a sufficient
quantity of water to which two or three per cent. of alum has been
added, until all the chromate is dissolved out, and they are then
washed in cold water and dried, and will look very inviting, especially
if white glue has been used. A similar result may be reached by using
a concentrated solution of cellulose in ammoniacal oxide of copper.
Thus if cylinders of unsized paper are formed with this paste, and
when thoroughly dry drawn through a parchmentizing solution (a cooled
mixture of 2 volumes of fuming sulphuric acid and 1 volume of water),
they will be beautifully parchmentized, and after the neutralization
of the acid, washing, etc., it will present a striking resemblance to
natural intestines.

_Tungstic glue._ This preparation offers an acceptable substitute for
hard India rubber. It is made by mixing a thick solution of glue with
tungstate of soda and hydrochloric acid, by means of which a compound
of tungstic acid and glue is precipitated, which, at a temperature of
86° to 104° F., is sufficiently elastic to admit of being drawn out
into very thin sheets. On cooling, this mass becomes solid and brittle,
and on being heated is again soft and plastic. It can be used for all
purposes to which hard rubber is adapted.

_Indestructible mass for the manufacture of ornaments, toys, etc._ A
mass, which is to have the hardness of horn, consists of 50 parts of
glue, 35 of wax or rosin, 15 of glycerine and the required quantity of
a metallic oxide, or mineral color. A soft mass consists of about 50
parts of glue, 25 of wax or rosin, and 25 of glycerine. The glue is
melted in the glycerine with the assistance of steam, and the wax or
rosin added. The latter in melting mixes with the glue and glycerine,
and finally the mineral color is added. The mass is poured in a liquid
state into moulds of plaster of Paris, wood, or metal. The degree of
hardness of the mass is increased by an addition of 30 to 35 per cent.
of zinc white, or other mineral color, according to the color the
article is to have.

_Compound for billiard balls._ Allow 80 parts of Russian glue and 10
parts of Cologne glue to swell up in 10 parts of water; then heat over
a water-bath, and when dissolved, add 5 parts of heavy spar, 4 parts
of chalk and 1 part of boiled linseed oil. Of a portion of the mass
form small sticks, dip them in the remainder, and allow the adherent
portion to dry, and repeat this process until a crude ball has been
formed. This is placed in a dry room for three or four months, and when
thoroughly dry, it is turned. The finished ball is placed in a bath of
sulphate of alumina for one hour, dried, and polished like an ivory
ball.

_Coloring glue._ Common black or dark glue, while possessing all the
adhesive and other essential qualities of fine colored glue, has
heretofore, owing to its color, been confined in its use to such
purposes in the arts where color was not essential.

The object of the following process, which is the invention of G. J.
Lesser, of Frankfort, Germany, is to color such glue so that it is both
refined and tinted, and may be used for various purposes in the arts.
It is especially applicable in the manufacture of sizing and finishing
compounds for paper hangings, compounds for the manufacture of elastic
rolls, for glue and size compounds for finishing yarns, textile
fabrics of silk, cotton, etc., for the manufacture of calcimines and
wall-coverings, for glue to be used with colored woods, and for all
other purposes where a fine, strong-colored glue is required.

For coloring common black or dark glue take a pound and a half of
liquid extract of lead and mix it into the water in which the glue has
been soaked, as follows: Thirteen pounds of glue, sixty-three and a
quarter pounds of water. Allow the glue to soak for about twenty-four
hours, then dilute it by a slow fire, and when heated gradually pour in
one and a half pounds of the extract of lead and mix it well together.

The extract of lead is a well-known commercial article, and it is well
suited for this purpose; but the inventor does not limit himself to
this particular preparation, as there are a larger number of neutral
and basic compounds of lead that may be so modified as to produce
results similar, if not identical, with the results obtained by the
formula above given. Gelatine may be treated instead of glue.

_Compositions for printing rollers._ All such compositions contain
gelatine or glue. The following receipts are used:

| I. | II. | III.| IV.| V. | VI. | VII.| VIII.
-------------+-----+-----+-----+-----+-----+-----+-----+-----+
Glue | 8 | 10 | 4 | 2 | 32 | 2 | 1 | 3
Molasses | 12 | — | 8 | 1 | 12 | 6 | 2 | 8
Paris white | 1 | — | — | — | — | — | — | 1
Sugar | — | 10 | — | — | — | — | — | —
Glycerin | — | 12 | — | — | 56 | — | — | —
Isinglass | — |1½ ozs.| — | — | — | — | — | —
India rubber| — | — | — | — | 10 | — | — | —
in naphtha

A patent roller composition is thus made: Gelatine 32 lbs. and glue
4 lbs. are softened in cold water and melted in a glue boiler. To
this are added 4 lbs. of glucose, 72 lbs. of glycerine, and 1 oz. of
methylated spirit. The whole is then digested for four to six hours
and cast into rollers. This composition is claimed to be unaffected by
temperature, to retain its elasticity, and not to shrink.

In practice it is found that all these compositions from the cleansing
and remelting become gradually sticky and useless. To partially
overcome this difficulty, formaldehyde is added to the roller
composition, which renders the glue insoluble in water, and thus
prolongs the life of the roller.

_Size._ This product is simply an undried glue and is used, not
for adhesiveness, but as a body for filling porous surfaces, such
as wood or plaster, stiffening and weighting textile fabrics, in
paper manufacture, and as a foundation for oil paints and varnishes.
According to Thomas Lambert, many firms who have a good selling
connection for size, do not go to the expense of erecting clarifying
plant and drying house for treating the glue-liquors, but prefer to
stop the process half way, as it were, and marketing the resulting
product as size. Others, again, with a complete glue plant at hand,
convert only a portion of their liquors into size, to meet trade
demands, the bulk going for the manufacture of glue. Size varies
in quality to suit the requirements of different trades. Cardboard
box-makers prefer a strong skin size, which is manufactured red or
yellow as preferred. A strong yellow size made from bone is used by
calico-printers, paper-stainers, wall-paper manufacturers, and in the
straw-hat and carpet trades.

In the preparation of skin-glue, the first and second liquors are used
for that purpose; the residual mass is then treated with water and
steam, which practically exhausts the gelatinous matter. This, the
third liquor, is used solely for size. During the boiling, samples
are taken at intervals, cooled, and the condition of the jelly noted.
The strength is also taken by the glue meter, which registers the
percentage. At a strength of 8 to 10 per cent. the liquor is run off,
passing through a filter of fine shavings or cloth, to remove any
suspended matter, into a wooden vat fitted with a steam coil, then
heated with a moderate charge of sulphurous acid to bring up the color,
and evaporated to a strength of 36 to 38 per cent., as may be desired,
and then run into casks to jelly. If skin-glue is not made, the three
runnings are used entirely for size.

An outline of a simple process used in an English factory devoted to
making tub-size, as given by Samuel Rideal, may be interesting.

The material is obtained from the tanyard ready limed and freed from
hair, and consists mainly of “faces” of bullocks or cows, the noses
being cut off as food for dogs. It is soaked again in weak lime water
and re-washed, then placed in coppers made of wrought-iron wielded
in one piece, and holding about 10 to 20 gallons, enclosed in outer
jackets of the same material containing water which is kept well
boiling. There are six coppers, about five feet high by three feet in
diameter. The charge of each is about ½ cwt. The material is covered
with water and well stirred with sticks for two hours, the scum and
dross being occasionally skimmed off and thrown away as useless. At the
end the size is ladled on to sieves, from which it runs into cooling
vats, and is filled while moderately hot into clean tubs.

The liquor is clear and of a light brown color for the best XX quality,
and darker for the common. The coolers or setting-backs are of wood or
zinc, and the liquid is not kept hot longer than it can be helped, as
it is liable to turn sour.

Bone-size is, according to Thomas Lambert, prepared as follows: The
bones are first degreased by the naphtha process, and then passed
through the cleanser direct into the glue-boilers and steamed, as in
the manufacture of glue. The resulting liquors are forced up to the
clarifying vats and partially bleached with a current of sulphurous
acid, passing through bag-filters to the evaporating troughs, and
concentrated from 30 to 38 per cent., as required, and then jellied in
casks.

The manufacturer with no benzine or glue plant at his disposal washes
the bones in a revolving drum, and, after crushing, they are fed into
a boiler and subjected to an alternate current of steam and water, the
latter coming from a spray pipe fixed at the top of the boiler. The
liquors are generally drawn in two portions, having a strength of 14 to
16 per cent. of glue. After separating the fat, which is refined and
sold to the soap-maker, the liquors are run into a large wooden vat
about 8 × 6 × 4 feet, fitted with a steam coil, partly bleached with
liquid sulphurous acid, and then boiled down to the required strength.

For a common size the bones are crushed but unwashed, and are fed
direct into the boiler and treated as above. The liquors are not
bleached, and boiled to a strength of about 25 per cent. glue. The
composition of the different grades may be given as follows:

Common size. 25 per cent. glue, 75 per cent. water, etc.
Medium size. 30 per cent. glue, 70 per cent. water.
Best size. 38 per cent. glue, 62 per cent. water.

A concentrated size is now prepared by many manufacturers. It is a
bone-size, and is sold at a Baumé strength at 122° C.

No. 1. 15° Bé. at 122° C., 40.5 per cent. glue.
No. 2. 20° Bé. at 122° C., 44.5 per cent. glue.
No. 3. 25° Bé. at 122° C., 49 per cent. glue.

Under the name of concentrated size also are sold a series of powdered
glues of different qualities. They are the off-color and twisted cakes,
sorted out in the warehouse, and ground to a fine condition by passing
through a mill, and their value is based on the quality of the cake
ground.

Size rapidly ferments and becomes sour and mouldy unless some
preservative is added. Sulphate of zinc is mainly used for this purpose.

_Bookbinders’ Size._—I. Water, 2 quarts; powdered alum, 1 oz.; Russian
isinglass, 2 ozs.; curd soap, 40 grains. Simmer one hour, strain
through linen or a fine sieve, and use while warm.

II. Water, 2 gallons; best glue, 1 lb.; alum, 4 ozs. Prepare and use as
above.

III. Water, 2 quarts; isinglass, 5 ozs.; alum, 240 grains.

_Water-proof Glue._—Solution of glue by itself or mixed with pigments
is used in painting walls in distemper. A water-proof coat is obtained
as follows: Boil 1 part of powdered gall-nuts and 12 parts of water
until the mass is reduced to two-thirds of its bulk. Then strain
through a cloth and apply the solution to the dry coat of distemper
paint, the latter becoming thereby as solid and insoluble as oil-paint.
The tannin of the gall-nuts acting only upon soft glue, the solution
has to be applied so the lower layer of glue becomes thoroughly soaked
through.

To render _wrapping paper_ water-proof the following glue-solution may
be used: Dissolve 24 parts of alum and 4 parts of white soap in 32
parts of water in one pot, and in another 2 parts of gum arabic and 6
parts of glue in 32 parts of water, and mix the two solutions. Heat
the mixture, immerse the wrapping paper in it, and pass it through hot
rolls, or dry upon twine stretched in frames.

_Fabrics may be rendered water-proof_ with glue and tannin. The process
is based on the fact that by the action of tannin or bichromates,
compounds insoluble in water are formed. It is, however, of first
importance that both solutions—tannin and glue—should fully penetrate
the fabric. If the latter is dipped directly into strong solution of
glue and then of tannin, the glue will only become insoluble on the
outside, and that which has penetrated deeper into the fibre will be
unchanged, having been protected by the superficial insoluble layer.
Hence, the treatment is commenced with a very weak solution of glue,
prepared by leaving glue broken small in hundred times its weight of
water for twenty-four hours. By that time the glue will have swelled
up, and the whole is boiled, whilst being constantly stirred, so as
to get a perfectly clear solution in which the fabric is boiled for
10 to 15 minutes. This time is no more than necessary for complete
penetration. The fabric is then well wrung between two rollers placed
over the glue-bath so that excess of solution runs back into it. The
fabric is then hung up, and when nearly dry is passed through a tannin
solution. The latter may be made from tannin itself, or from a tannin
extract, or by boiling galls or oak bark in water. The tannin solution
can be used fairly strong, as only so much of it is taken up as
corresponds to the glue present, and it can be used over again as long
as it can supply the tannin required, and can then be reinforced with
more tannin as required.

It is not necessary for the fabric to stay long in the tannin, as it
reacts quickly with the glue. The tanned material is again hung up
to dry, and when quite dry is washed in plain water to remove any
excess of tannin. The whole process from the beginning is then twice
repeated. After this second repetition there is so thick a layer of
tannate of gelatine on the fabric that the dry cloth has acquired
considerable solidity and a smoothness which recalls that of leather.
The fabric is now passed through a stronger glue solution, using three
or even four parts of glue per hundred of water, but never exceeding
the latter limit. After the glue-bath the fabric goes through the
tannin bath, whereby it becomes quite thickly coated with tannate of
gelatine. By repeatedly treating with glue and tannin alternately,
this coating can be made as thick as desired, and finally masses are
obtained in which the texture of the fabric is entirely hidden, and
especially after the fabric has been calendered under heavy pressure
after water-proofing. The color acquired by goods thus water-proofed is
a more or less dark leather-brown.

Muratori and Landry treat the fabric with a solution made in three
separate operations:

1. Potash alum 100 lbs. dissolved in 10 gallons of boiling water.

2. In another vessel 100 lbs. of glue are soaked in cold water till the
glue has trebled in weight. The remaining water is poured off, and the
glue liquefied by the application of heat. When the glue is boiling, 5
lbs. of tannin and 2 lbs. of soda water glass are put in it.

3. The two solutions are boiled together, being stirred constantly.

When the mixture is complete, it is allowed to cool to a jelly. To
water-proof the goods some of the jelly is boiled with water (1 gallon
to 1 lb., or a little over) for three hours, adding water to compensate
for evaporation, so as to keep the volume of the solution constant,
as shown by tests of its specific gravity with a hydrometer. The bath
is then allowed to cool to 176° F., and the fabric is soaked in it
for half an hour and then stretched out horizontally for six hours
to drain. The fabric must be kept horizontal, so that the solution
remains uniformly distributed through it. The drainings are collected
to be used over again. The fabric is then dried in the open air or in a
drying room, still in the horizontal position. If a drying room is used
the temperature of it should not exceed 122° F.

Muzmann and Krakowitzer dissolve 10 lbs. of gelatine and 10 lbs. of
tallow soap in 30 gallons of boiling water, and mix the solution in
4 gallons of water in which 15 lbs. of alum have been dissolved. The
whole is boiled for half an hour, and then allowed to cool to 104°
F. At that temperature the fabric is thoroughly soaked in it, dried,
rinsed, again dried, and finally calendered. In this process the alum
partially decomposes the soap, forming either free fatty acid or an
acid alumina soap. The gelatine forms an insoluble compound with the
alum. The free fatty acid or acid soap is mostly carried down on the
fibre by the precipitate formed by the alum and the gelatine.

_Glue for Joints in Leather Driving Belts._—Soak equal parts of good
hide glue and isinglass in water for 10 hours, and then boil with pure
tannin till the product becomes sticky. The surfaces to be cemented
together should be roughened and the glue applied hot.

According to another method 2 lbs. of best glue are dissolved at a
moderate heat in 3 lbs. of water and about 3 drachms of carbolic acid
stirred into the hot solution. The mixture is poured into shallow iron
pans to congeal, when it is cut in pieces and dried in the air. For use
the glue is liquefied by adding a small quantity of vinegar and applied
with a brush to the leather. The joint is finally pressed between iron
plates at a temperature of about 77° F.

_Hectograph Mass._—Soak a good quality of glue for 24 hours in
sufficient cold water to cover it. Then take the swelled glue from
the water and melt it in an enameled pot over a moderate fire. When
perfectly liquid add the required quantity of glycerine (see formulas
below) and intimately mix both by continued stirring.

The vessel containing the mixture should for some time be kept hot, so
that the mass remains thinly fluid. The purpose of this is to allow
the air-bubbles formed by stirring to rise to the surface. If any scum
is formed on the surface, remove it carefully with a shallow spoon.
The composition is then ready to be poured into the vessel intended
for its reception, which may be made especially for the purpose, or a
shallow baking pan of tin may be used. When the pan is filled with the
composition place it perfectly level in a cool place free from dust and
allow to remain at least for several hours.

_Formulas for Hectograph Masses._—I. Gilder’s glue, 100 parts;
glycerine of 28° Bé., 500.

The glue is allowed to swell in water, as described above, then melted,
mixed with the glycerine, and evaporated to the required consistency.

II. Gilder’s glue, 100 parts; glycerine of 28° Bé., 400; water, 200.

CHAPTER IX.

MANUFACTURE OF GELATINE, AND PRODUCTS PREPARED FROM IT.

Gelatine, like glue, is produced from hides and skins, and bones. It is
distinguished by its purity, has a slight yellowish tint, and is very
hard and elastic. In cold water it softens, swells up, becomes opaque,
but does not dissolve. In hot water it dissolves completely, and on
cooling for several hours, an almost colorless, transparent and very
firm jelly results. This property of becoming jellied is in part lost
if the solution is for some time exposed to a temperature higher than
212° F.

The chemical constitution of gelatine is entirely changed by
concentrated sulphuric or nitric acid. Concentrated acetic acid, on the
other hand, renders softened gelatine transparent, and then dissolves
it; the solution does not become viscid, but preserves its adhesive
property. Dilute acids have no appreciable effect either on the
coagulating or the adhesive power.

Tannin is a valuable and delicate test of the presence of gelatine.
When added to a solution containing only 1/5000th part of gelatine,
nebulosity is immediately apparent. When more concentrated gelatinous
liquors are treated with tincture or infusion of nut gall, a dense,
white, caseous subsidence occurs which, on desiccation, becomes
brownish-yellow, agglutinates, and forms a hard, brittle mass easily
reduced to powder.

Gelatine is much used for culinary and medicinal purposes, and for
fining beer, wine and other liquids. Considered medicinally, it is
emollient and demulcent, and for this end is dissolved in water or
milk, and rendered palatable by the addition of acid and sugar. In
pharmacy, it is used for the formation of capsules intended to conceal
the nauseous odor and taste of medicinal preparations inclosed in them.
It is likewise employed for coating pills.

SKIN GELATINE.

But few changes have been made in the process of manufacturing skin
gelatine since the method introduced and patented, in 1839, by George
Nelson. This patent relates to the preparation of a transparent
gelatine from waste of calf skins, and of an inferior variety from
other skins freed from hair, wool, and fleshy and fatty matters. The
mode of procedure is the same in both cases, and is as follows: The
cuttings being washed are macerated in solution of caustic soda or
caustic potash at a temperature of 60° F., until they are partially
softened. Ten days is the average period required to effect this.
They are then placed in closed vessels and permitted to remain until
a thorough softening is effected. They are now washed in a revolving
cylinder, through which a current of water passes to free them from
adhering alkali; exposed in a well-closed chamber to the action of
sulphurous acid, and finally submitted to pressure to remove the
adhering water. The softened mass bleached by sulphurous acid is then
placed in a suitable vessel and subjected to the action of steam until
it is, as far as possible, dissolved. The liquor is then strained
and set aside at a temperature of 100° to 120° F. for the impurities
which may have remained to subside. The clarified solution is poured
upon slabs of slate or marble to the depth of about half an inch and
allowed to remain there till sufficiently solidified, when it is cut,
and washed to remove all traces of acid. It is subsequently redissolved
by means of a steam bath at a temperature of 95° F., finally again
solidified, and dried by exposure to dry air upon nets.

Messrs. J. and G. Cox, of Edinburgh, patented in 1844, a process by
which a perfectly pure substance, superior to that prepared from
isinglass is obtained. Shoulders and cheeks of ox-hides are preferred
by the patentees. They are thoroughly cleansed in water, after which
they are cut into pieces by a machine similar to that used for cutting
straw, and then subjected to the action of a paper-maker’s pulp-mill.
By this process the gelatinous fibre is well washed and cleansed, as
a stream of water flows through the mill during the whole operation,
carrying off all the impurities. The comminuted material is next
pressed between rolls, mixed with fresh water, sufficient to effect its
solution, and heated to a temperature varying from 150° to 212° F. The
resulting gelatine-solution is then allowed to cool to 150° F., and
mixed with fresh bullock’s blood—1 part of the latter to 700 parts of
solution. At a somewhat increased temperature the albumen of the blood
coagulates and rises in the form of foam to the surface, or subsides
in the shape of flakes, carrying with it the impurities, and thus
clarifying the liquor. The latter is allowed to stand for some time,
when it is poured upon stone slabs and allowed to solidify.

G. P. Swinborne’s improved patented process for the preparation of
gelatine from hides, skins and glue pieces, relates mainly to the
cleansing of the raw material. The latter is reduced by means of
suitable instruments to shavings or slices, and soaked in cold water,
which is drained off and replaced by fresh water three times a day,
until no odor or taste is perceptible. The shavings are then heated
with water, not above boiling, strained through filter cloths, and the
liquor is then run on to slate or other material to dry.

The modern process of preparing skin gelatine is, according to Thomas
Lambert, carried out as follows: The first treatment the cleansed skins
undergo is the “steeping” process with caustic soda or milk of lime.
In some factories a mixture of caustic (slaked) lime and soda ash is
used, in the proportion of 6 lbs. soda ash and 6 lbs. slaked lime to
every hundred-weight of skins treated, the chemical change being that
the whole of the carbonate of soda (soda ash) is converted into caustic
soda by its equivalent of caustic lime, the excess of the latter
remaining as such. The equation representing this is—

Na_{2}CO_{3} + CaH_{2}O_{2} = 2NaHO + CaCO_{3}
Soda ash. Caustic lime. Caustic soda. Carbonate of lime.

This steeping is conducted in large wooden vats, each having a length
of 12 feet, width 8 feet, and depth 3 feet, and fixed with a slight
gradient to the overflow, which is placed at the most convenient corner
of the vat and protected by perforated boards. The skins in the vat
are nearly covered with water, and then the solution of caustic soda,
or the slaked lime mixed in water to a cream, is sprayed equally over
the mass, the whole being intimately mixed with long stirring poles.
The water is renewed twice during a period of 12 days, the time allowed
for the skins to soak. They are now removed to a chamber, in which a
moderate increase of heat facilitates the saponification of the fat and
the dissolving of the fleshy matter. The chamber is a brick building,
with a cemented floor, on which the skins are spread to a uniform depth
of about six inches and is heated by steam pipes running round the
building. At a temperature of about 70° F. the skins are exposed two
or three days, with frequent turning. They are now transferred to the
washing machine and washed until the effluent is practically free of
soda or lime. The skins then undergo a bleaching process to whiten, and
thus destroy any injurious coloring matter. For this purpose the washed
skins are removed to a number of vats fitted with folding covers, and
treated to a solution of sulphurous acid of ½° Twaddell strength for 24
hours, each vat being well stirred at intervals to allow the “bleach”
to permeate equally the mass.

In some factories this process is carried out with dry sulphurous
acid, the gas being generated in a sulphur burner and, after washing,
passed into a chamber containing the skins. The vats are now drained,
then filled up with water, well stirred, and the water run off. This
is repeated until the effluent is practically free of any sulphurous
smell, and the work of dissolving the gelatine is proceeded with.
The digesting of the skins is carried on in stoutly built, circular
wooden vats, each having a size, generally of 4 feet 6 inches diameter
and 6 feet deep, and fitted with 2¼ inch copper steam coil. The vats
are provided with a double wooden bottom to divide the heat. They
are arranged on the first floor of the building, the liquors running
through a shallow filter of fine copper gauze to the clarifying vats
beneath. The skins are raised by an elevator and fed direct into the
vats by suitably-arranged troughs, then covered with water, and steam
is sent through the coils. The temperature is frequently taken by the
thermometer and should never exceed 177° F. During the digestion,
any unsaponified fat and dirt comes to the surface as a scum, and is
carefully skimmed off from time to time. Samples are also drawn of the
liquors, cooled, and the appearance and strength of the jelly noted.
After five to six hours’ heating, the first liquors are run off to the
clarifying vats, at a strength of about 17 per cent. gelatine.

The vats are refilled with water, and a second digestion made, the
liquor running to the clarifying vats at a strength of 12 per cent.
In the third digestion the temperature is raised a few degrees to
practically exhaust the gelatinous matter, and can either be clarified
to form an inferior gelatine, or concentrated for size. The exhausted
matter is taken to the manure-shed for mixing purposes. The clarifying
of the first and second liquors—and if used for gelatine the third
liquor—is done separately in the clarifying vats. The clearing agent
used is alum, to the extent of ½ per cent., or a little blood diluted
with water; both are mixed with a small portion of the hot liquors in
a bucket, and then well stirred in the vats. The liquors are raised
to 177° F. to coagulate the impurities, and then lowered to 149° F.
and allowed to stand for two hours. During this time the coagulated
matter rises to the surface, and is skimmed off. On leaving the vats,
the liquors are filtered through fine copper gauze into a receiver from
which is fed the vacuum pan.

Gelatinous liquors being peculiarly sensitive, especially as regards
color, to high temperatures, it is found advisable to evaporate them in
vacuo; and this method is adopted by all continental makers. The three
grades of the liquors, concentrated to the required strength, are run
on to squares of glass, 4´ × 4´, fixed in a wood framing, to a depth
of ½ inch for cake and ¼ inch for leaf gelatine, then placed perfectly
level on racks for jellying. In 24 hours the jelly is firm, and can
be easily cut to the desired size of cake or leaf wanted. A very fine
gelatine is produced by cutting the jelly into small pieces, washing
well with cold water, and remelting at a temperature of 176° F., and
poured again on the glasses for jellying.

The drying is carried on by exposing the cut cakes, on nets fixed to
a framework of wood, to a rapid current of dry air in the tunnels, as
described in the drying of glue.

BONE GELATINE.

The materials used for this purpose should be of the best description,
the most suitable bones being calves’ feet, waste of turners and button
makers, the bony cores of the horns of the ox and cow. Such bones do
not require comminution, but if large bones of oxen, horses, etc., are
to be used, it is recommended to break them as small as possible by
means of a wooden mallet, and to avoid the use of iron stampers, as the
bones become heated by the heavy blows and friction to which they are
subjected during the process, and acquire an empyreumatic odor which is
retained by the gelatine.

The next step in the process is the solution of the glue cartilage.
This was formerly effected by the use of steam and water. The crushed
bones were placed in a wire basket or cage and this inserted in a small
cast-iron cylinder and steam introduced. The apparatus is connected
with a steam boiler, and provided with an air-tight lid, and a pipe
and a rose connected with a water reservoir for pouring water over
the bones in order to promote the solution of the glue cartilage. But
this process is very slow, 20 hours being required without completely
exhausting the bones.

The resulting gelatinous liquor is drawn off every hour, the first run,
which contains the dirt and grease, being, of course, kept separate
from the rest.

[Illustration: FIG. 59.]

As will be readily understood this process consumes much fuel, and
leaves a residue which, though not completely exhausted, cannot be
further utilized for the preparation of gelatine. In fact the entire
process is obsolete, but as it is still in use in some localities,
a description is here given, for the sake of completeness, of the
apparatus and improved manner of manufacture employed in the factory of
D. J. Briers, which is well known for the beautiful product turned out.

Fig. 59 shows a longitudinal section of the entire apparatus.

Fig. 60 is the horizontal section of the boiler.

_a_, is the cylindrical boiler 6 meters (19.68 feet) long, and 2
meters (6.56 feet) in diameter. It is made of strong boiler plate
doubly riveted, and capable of resisting a pressure of six or seven
atmospheres.

_b_, is the manhole. It is closed by an oval lid secured by two iron
rods and two bolts, so that after placing the lid in position, the
boiler is hermetically closed by tightening the nuts upon the bolts.

_c_, is a cast-iron fork with two safety valves with levers graduated
from 1 to 100 atmospheric degrees.

[Illustration: FIG. 60.]

_d_, is a float upon the surface of the water, and provided with a
wheel graduated from Nos. 1 to 6. Its object is to indicate during the
operation how much water is lost and how much remains in the boiler.
Care must be had not to allow the indicator of the wheel to get below
No. 1. This figure indicates that the water has reached the highest
point in the boiler exposed to the fire, which is consequently the
lowest point which the water can be allowed to reach. On the other hand
the indicator must not move above No. 6, as the water when standing
too high in the boiler and too close to the pipes conducting the steam
into the various apparatuses might mix with the steam and spoil the
operation carried on in the drum, _e_, Fig. 60.

_f_, Fig 60, is a manometer, which indicates the degrees of pressure
exerted by the steam in the interior of the boiler. It consists of
a wrought-iron pipe bent double, and is filled with mercury 1.22
meter (4.002 feet) high counted from its base. One end of the pipe
communicates with the boiler, while the other end is provided with a
small brass wheel. Upon the latter is a thread of twisted silk, to
the end of which is suspended an iron cylinder of somewhat smaller
circumference than the bore of the pipe, so that it can move up and
down in it without friction. This cylinder rests always upon the
mercury. To the other end of the thread is fastened an indicator of
somewhat less weight than the cylinder, which, by sliding in a groove
in a graduated board placed alongside the pipe, indicates the degrees
of steam pressure.

_g_ is a cast-iron pipe for heating the drying room, and

_h_ another cast-iron pipe for heating the store-room for the bones.

_i_ is the forcing pump for feeding the boiler with water.

_k_ is a sheet-iron reservoir placed close to the end of the boiler.
It is filled with water, which is heated by the heat lost in the
fire-place in consequence of the draught, and by allowing the smoke
to circulate under the reservoir before passing into the chimney. The
reservoir communicates with the forcing-pump by means of a pipe and
stopcock, so as to avoid feeding the boiler with cold water.

_l_ is the fire-place, consisting of the grate, door and cast-iron
frame.

The drum, _e_, is a spherical vessel of strong sheet-iron doubly
riveted. It is 3 meters (9.84 feet) in diameter, and capable of
resisting a pressure of six to seven atmospheres. It serves for
softening the bones with the assistance of steam passed into it from
the boiler, _a_. It is provided with a manhole similar to that of the
boiler.

_n_ is a wrought-iron shaft passing horizontally through the drum and
revolving in the brasses, _o_.

_g_, Fig. 61, is a gearing with a crank, by means of which the drum _e_
is revolved. The power of the gearing must be so calculated that one
man can turn the wheels when the drum is filled with water.

[Illustration: FIG. 61.]

_r_ is a false bottom perforated in its entire length with holes 12
millimeters (0.47 inch) in diameter, and is placed about 15 centimeters
(5.9 inches) above the true bottom of the drum. It consists of two
pieces, and is secured by two nuts, so that it can be easily removed
and replaced. Its object is to prevent the bones from clogging up the
pipe _s_, and the cocks _t_, _u_.

_a_, _a_, Fig. 61, are angular iron points inside of the drum _e_.
Their object is to facilitate the shifting of the bones when the drum
is revolving.

_x_, Fig. 59, is a cock near the manhole. It is opened about 2
millimeters (0.079 inch) during the operation in the drum. It serves
also for the escape of the steam from the drum when the operation is
finished.

The cocks _t_, _u_, placed in the lower part of the drum, serve for the
escape of steam condensed during the operation.

The steam pipe _p_, Fig. 59, conducts the steam from the vessel _a_
into the drum _e_.

_y_, Fig. 59, is a cock graduated into eight equal parts and placed
on the steam pipe _p_, to conduct the steam from the box _z_, into the
stuffing box _a´_, and from there into the pipe _s_, then under the
false bottom _r_, into the drum _e_.

The lid of the cast-iron box _z_, is provided with a safety valve
loaded with a weight corresponding to the pressure of one atmosphere.

The wooden vessel or box _d_, the ground-plan of which is shown in Fig.
62, serves for boiling the comminuted bones in order to extract the
jelly. This box consists of the following parts:—

[Illustration: FIG. 62.]

_n_, are cast-iron steam pipes occupying the entire surface of the box,
being placed at equal distances from each other, and connected on their
ends by semicircular pieces. The steam, which is allowed to circulate
in the pipes in order to boil the liquid, enters through one of the
ends which rises up vertically and is connected with the cock _h´_,
Fig. 59. The other end is secured to the inner side of the box, which
is perforated for the admittance of the cock _o´_. Upon the steam pipes
lies a wooden framework with linen nailed upon it, the object of which
is to prevent the comminuted bone substance from falling under the
pipes. The frame must, of course, fit closely into the box.

The cock _h´_ graduated in eight equal parts serves to admit steam into
the pipes _n´_, and is opened either entirely or half, or one-quarter,
or one-eighth, according to the stronger or gentler ebullition to be
produced.

To prevent the steam from becoming stagnant in the steam pipes _n´_,
a small jet is allowed constantly to escape through the cock _o´_. The
latter serves also to run off the condensed steam when it no longer
possesses the heat required to keep up ebullition.

_p´_, Fig. 62, is a cock in the bottom of the box _d´_ for drawing off
the gelatinous solution from the residue. The box _e´_, Fig. 62, a
ground-plan of which is shown in Fig. 63, serves for evaporating the
gelatinous solution, which is effected by circulating steam through
several tubular pieces of cast-iron which form the bottom of the box
and are connected in a similar manner as the pipes in the box _d´_.

The cock _i_ is graduated and similar to _h´_.

[Illustration: FIG. 63.]

The cock _r´_, Fig. 63, is similar to _o´_, Figs. 59 and 62.

_s´_, Fig. 63, is a cock for drawing off the evaporated gelatinous
solution.

The wooden box _f´_, Fig. 59, a ground-plan of which is shown in Fig.
64, serves for the reception and settling of the evaporated gelatinous
solution. Its bottom is constructed in a manner similar to that of the
box _e´_.

[Illustration: FIG. 64.]

The cock _n´_, which is placed 14 millimeters (0.55 inch) above the
bottom of the box, serves for running the gelatinous solution into the
wooden cooling-boxes.

The bones as received in the factory are sorted by throwing out the
spongy material, etc. They are then steeped in lime-water for a few
days to free them from adhering particles of flesh, after which they
are dried and stored away for future use.

The boiler _a_, is filled two-thirds with water, and heated until the
manometer indicates a pressure of 30°. In the meanwhile the drum _e_,
is filled seven-eighths with perfectly dry bones, and steam is then
admitted from the boiler _a_, through the graduated cock _y_. The fact
that the bones in the drum are exposed to the proper temperature of
250° F. is recognized by the thermometer _b´_, placed between the cock
and the drum.

To prevent the stagnation of the steam in the drum, _a_ small jet of
it is allowed constantly during the operation to escape through the
cock _x_. The cock must not be opened wider than is necessary to keep
the temperature at 250° F. By opening it wider, this degree would be
exceeded, and the gelatine-yielding substance would, in consequence,
undergo alteration. A quarter of an hour after admitting the steam into
the drum, the cock _t_, is opened, and again closed after allowing a
small portion of the condensed steam to escape to the cock _u_, and,
through this, into a box. This operation is repeated every quarter of
an hour.

To change the position of the bones, the drum is revolved twice every
half hour, by means of the gearing _q_, of course closing the cock _x_
during the operation.

By carefully following the above rules, the bones will be thoroughly
reduced in four hours. If, for instance, steam has been introduced into
the drum at 5 o’clock a. m. the operation will be finished at 9 a. m.
The cock _y_, is then closed, and the steam allowed to escape through
the cock _x_. After the escape of the steam, the drum is emptied, by
removing the lid and turning it upside down. It is then refilled with
entirely dry bones, and the operation continued in a like manner, day
and night, if necessary.

After the bones have been taken from the drum, they are spread out
under a shed, and, when dry, ground in a suitable mill. The resulting
flour, which contains the jelly-yielding substance, is brought into
the vessel _d´_, which, in the meanwhile, has been furnished with
sufficient water to cover the flour 65 centimeters (25.59 inches) deep.
The mixture is boiled for three-quarters of an hour, being constantly
stirred to prevent the flour from forming a heavy and dense mass
which would hinder the quick extraction of the jelly. Ebullition is
then interrupted by closing the cock _h_, and the fat floating on the
surface skimmed off. After allowing the gelatinous solution to settle,
it is drawn off by means of a faucet placed above the level of the
flour. Thirty bucketfuls of the gelatinous solution are then at once
poured into a vat and mixed with the condensed steam drawn off by means
of the cocks _t u_, during the reduction of the bones in the drum.
After allowing the mixture to cool to 160° to 155° F., 20 kilogr. (44
lbs.) of pulverized alum are added at once and as quickly as possible.
When the gelatinous solution has become transparent, it is drawn off
into the box _e´_, and a few bucketfuls of hot water are poured upon
the sediment in the vat in order to extract the remaining jelly, which
is effected by thorough stirring and allowing to settle until the water
is entirely clear.

After disposing of the 30 bucketfuls in the manner mentioned,
the remainder of the gelatinous solution is evaporated. This is
accomplished in the box _e´_, which is filled 8 centimeters (3.15
inches) deep with gelatinous solution, and steam is then admitted
into the tubular bottom pieces. To promote evaporation and keep the
fluid constantly in motion, the cock _i´_ is only opened far enough
to keep up gentle ebullition. During evaporation the solution should
be frequently stirred with an implement resembling a rake. The nearer
the required degree of concentration is approached, the greater care
must be exercised to prevent the solution from boiling too strongly.
The proper degree of consistency is obtained when half a saucer full
of the solution placed in a shady place in the air acquires in a short
time such a consistency that when touched with the finger no impression
remains. The cock _i´_ is then closed, and the jelly is drawn off into
the box _d´_, which contains the 30 bucketfuls of clarified jelly,
care being had to mix the two solutions as quickly as possible. After
evaporating all the gelatinous solution and mixing it in the box _d´_,
the whole is heated to 158° F., by admitting steam through the cock
_k´_, care being had not to forget closing it as soon as the above
temperature has been reached. The solution is then thoroughly stirred
and permitted to settle for three hours to allow of the precipitation
of the lime salts decomposed by the alum. The fluid, which is now
perfectly transparent and of a beautiful dark-yellow color, is then
drawn off into wooden cooling boxes 2 to 2.5 meters (6.56 to 8.2 feet)
long, 20 centimeters (7.87 inches) wide, and 16 centimeters (6.30
inches) deep. The following day the gelatine is cut into leaves 25
centimeters (9.84 inches) long and 12 centimeters (4.72 inches) wide,
which are dried upon nets. When quite dry, the drying process is
finished by bringing the leaves into the drying-room which is heated by
the pipe _g_. (Fig. 59.)

The bone flour remaining in the box _d´_ still contains much jelly,
which is extracted by pressure. This is accomplished immediately after
running off the gelatinous solution into the evaporating vessel. The
liquid which has drained through the cloth frame previously mentioned,
is drawn off by opening the cock _p´_, Fig. 62, while the residue
in the box _d´_ is placed in coarse bags and the jelly extracted by
subjecting the bags to strong pressure under an iron screw-press.
Before mixing the extracted fluid with the solution in the evaporating
vessel, it is recommended to allow it to settle, as it is always more
or less turbid. The residue remaining in the bags is an excellent
manure.

The modern process of preparing bone gelatine, which is now almost in
general use is as follows: Clean bones are selected for the purpose,
and the operation commences with the extraction of the fat by means
of benzine, though some manufacturers prefer carbon disulphide as a
solvent, because it is claimed that by reason of its low boiling-point
it does not injure the gelatine in the same manner as benzine, and
besides it leaves no smell in the degreased bones. It is advisable
to bleach the degreased bones, spread out in thin layers and kept
constantly moist, by exposure to the action of air and light. The
bleached bones are conveyed to large vats for the purpose of extracting
their mineral constituents by digestion with hydrochloric acid. If
the gelatine is to be used as an article of food, or for medicinal
purposes, only the purest hydrochloric acid obtainable should be used,
while the ordinary article suffices for that for technical purposes.

The vats are filled three parts full with bones and the latter covered
with a solution of hydrochloric acid of 10 per cent. strength.
Digestion is carried on until the bones become soft, flexible and
semi-transparent. The acid water is now drained off, and a supply of
fresh water added, and then discharged. This is repeated until the last
water is entirely free of acid, which is known by adding a few drops of
silver nitrate, the absence of any white precipitate indicating that
the water is entirely free of acid.

The bones are now bleached in the manner as described under
skin-gelatine, preferably with solution of sulphurous acid, the
process with gaseous sulphurous acid being difficult to carry out and
considerable time is required for the gas to completely permeate the
cartilaginous mass. The bleached bones are then conveyed to the boiling
vats and the resulting liquors treated in the same manner as described
under skin-gelatine.

As bone-gelatine solidifies with a larger content of water than the
product from skins, evaporation of the liquors may be early interrupted
and the resulting jelly cut into thin leaves which are finally dried.

COLORED GELATINE.

Cakes or leaves not entirely colorless may be utilized for colored
gelatine which is employed for various purposes. Coloring is effected
by simply dissolving and distributing uniformly a suitable quantity
of coloring matter in the clarified gelatine liquor previous to
solidifying; of course only water-soluble coloring matter should be
used.

Colored gelatines are frequently used by confectioners and in the
household in the preparation of jellies, and the use of poisonous
colors should under all conditions be avoided. Sufficient attention is
not paid to this, because many of the aniline colors which are now so
much used for the purpose are at least open to suspicion, while others,
especially picric acid, which yields a beautiful yellow color, are
decidedly poisonous.

The following coloring matters are perfectly harmless and yield good
results in coloring gelatine:

_Yellow_: Caramel or sugar color. A still more beautiful yellow is
obtained by the use of an aqueous extract of saffron.

_Red_: Extract of cochineal.

_Blue_: Indigo-carmine solution.

_Green_: Mixture of indigo-carmine and caramel.

_Violet_: Mixture of extract of cochineal and indigo-carmine.

While gelatine colored with the above-mentioned coloring matter does
not present such a beautiful appearance as the product colored with
aniline colors, it is entirely harmless and suitable for culinary
purposes.

Leaves of gelatine colored with aniline colors exhibit beautiful colors
and are used for many technical purposes. The following colors may be
employed:

_Yellow_: Picric acid soluble in hot water.

_Red_: Fuchsine or eosine.

_Blue_: Water-soluble blue.

_Green_: Iodine green.

_Violet_: Methyl violet.

_Gelatine for Fining Purposes._

For fining beer, wine, etc., gelatine in leaves or in powder is brought
into commerce. For the preparation of leaves, gelatine particularly
well dried is carefully melted over a water-bath and then ladled into
sheet-metal moulds, and allowed slowly to solidify.

The product brought into commerce under the name of _Gelatine Lainée_
which commands a high price is in many cases nothing but thoroughly
purified bone-glue of a dark honey-yellow to brown color.

Fining powder for wine and beer is made by grinding off-color gelatine
cakes and freeing the resulting powder from coarser pieces by sifting.
The powder is white.

_Liquid fining gelatine._ This preparation consists of
gelatine-solution suitably prepared, and represents a colorless, or at
the utmost slightly opalescent, product just sufficiently concentrated
to remain liquid.

Skin-liquors can only be used for the preparation of liquid gelatine,
as bone-liquors already gelatinize when they contain scarcely more than
1 per cent. of glue. The skin liquors are concentrated so far as to
remain liquid at a temperature of from 60° to 68° F.

A product answering all demands is obtained as follows: A good quality
of gelatine of a pale color is dissolved in a sufficient quantity of
water, the solution, in case it shows a slight odor, filtered through
animal charcoal, and then brought into bottles. To prevent putrefaction
the liquid gelatine is sterilized as follows:

The filled bottles being placed in a boiler filled to a proper depth
with water, the latter is slowly brought to boiling which is kept up
for 15 to 20 minutes. The bottles are then closed with corks previously
boiled in the water.

_Preparation of Gelatine from Ordinary Glue._

For this purpose ordinary pale-colored glue is allowed to swell up
for two days in cold strong vinegar. The vinegar is then drained off
and the glue which is now almost colorless, is placed upon a sieve and
allowed to float in a vessel filled with water for 10 to 12 hours. It
is then placed upon a linen cloth, stretched in a room heated to at
the utmost 68° F., allowed to drain and dry to such an extent that
on heating it to between 158° and 167° F., a thick clear liquid is
obtained. This liquid is carefully poured upon plates of glass or
marble, so as to avoid the formation of air bubbles and when solidified
the leaves are removed and completely dried in the air. The product
thus obtained being entirely tasteless and almost colorless may be used
in the preparation of jellies, as well as for foils for pictures, etc.

_Preparation of Gelatine for Photographic Printing and for Photographic
Purposes in General._

Gelatine suitable for this purpose should be colorless and free from
all salts, since the latter would exert a disturbing effect upon the
chemical processes which take place during the photographic operation.
For the removal of the salts the gelatine is treated as follows:
Colorless gelatine of the best quality is broken into small pieces and
covered with 10 to 12 times the quantity of water, the latter being
changed every 15 to 20 minutes until the last water shows no trace
of lime, which is known by adding to the water solution of oxalate;
the absence of turbidity indicates that the water is free from lime.
The white of an egg is now mixed with five drops of ammonia and twice
the volume of distilled water and shaken to froth in a bottle. This
quantity suffices for 6 to 8 ozs. of gelatine. The washed gelatine is
next melted in a dish and mixed with the white of egg. One part of
glacial acetic acid mixed with 250 parts of water is then added drop
by drop, stirring constantly until sensitive litmus paper shows an
acid reaction. The liquid is now rapidly brought to the boiling-point,
whilst stirring constantly, and then filtered in a warm place to avoid
gelatinization. The gelatine now contains only the salts of the white
of egg, some ammonium acetate and free acetic acid. For their removal
the solidified gelatine is cut into pieces, which are placed in water.

_Gelatine Capsules for Medicinal Purposes._

Considerable use is made of gelatine in medicine. To disguise the
disagreeable taste of some medicines they are either mixed with
gelatine solution or inclosed in gelatine capsules. To prepare the
latter, dissolve 8 parts of gelatine, 2 of sugar, and 1 of gum-arabic
in 8 of water in a water-bath, and dip the pear-shaped ends of iron
rods into the lukewarm solution. To facilitate the detaching of the
gelatine film from the rods, grease the pear-shaped ends with oil. The
capsules are dried by placing them in holes of a corresponding size
in boards. When dry they are filled with the respective medicine, and
closed with a drop of the same solution.

_Court Plaster._

Gelatine or isinglass 155 grains, alcohol 13½ fluid drachms, glycerine
15½ grains. Water, tincture of benzoin, each a sufficient quantity.
Dissolve the gelatine in a sufficient quantity of hot water to make the
solution weigh 4½ ozs. Spread one-half of this in successive layers by
means of a brush upon taffeta stretched upon a frame so as to present
a level surface, waiting after each application until the layer is
dry. For the first two applications the gelatine solution should be
warmed merely to above its congealing point, so that when spread out
it may rapidly solidify and at the same time adhere to, but not pass
through the fabric. Mix the second half of the gelatine solution with
the alcohol and glycerine, and apply it in the same manner. Then
reverse the taffeta, coat it on the back with the tincture of benzoin
and allow it to become perfectly dry. The tincture of benzoin applied
to the reverse side leaves a thin layer of resin which in a measure
renders the plaster water-proof; it is, however, advisable to repeat
this application once or twice. The addition of glycerine to the last
portion of the gelatine solution prevents the plaster from breaking,
and preserves its flexibility for a long time. When the plaster is dry
it is cut in pieces of suitable length and preserved in well-closed
vessels.

_Gelatine Foils._

Large quantities of gelatine foils, which are leaves of gelatine about
as thick as a sheet of paper, are produced in England and France where
their manufacture forms a special branch of industry. They are either
simply colored or printed with neat designs in gold or silver.

The fabrication is quite simple. Cover pure gelatine with water, and
after swelling up, pour off the water and dissolve the jelly over a
water-bath. After allowing the solution to cool somewhat, add the
coloring matter previously dissolved in water.

In place of pure gelatine, a solution of ordinary bone-glue may be
used. In order to clarify it add O.14 oz. of oxalic acid dissolved in
water to every 5.5 lbs. of glue. To make the foils more flexible add
also one-half pint of spirit of wine and O.28 oz. of rock candy or a
small quantity of glycerine.

Aniline colors soluble in water are best adapted for coloring the
foils; for _red_, fuchsine, eosine or ponceau, for _blue_, _blue de
Parme_, for _green_, aldehyde green, for _yellow_, picric acid, and for
the various shades, mixtures of the above colors.

A durable blue is also produced by indigo solution, yellow, by
decoction of saffron, green, by mixing blue and yellow, red, by a
solution of carmine in spirit of sal ammoniac, and violet, by mixing
blue and carmine.

The gelatine solutions are poured upon ground-glass plates, previously
polished with elutriated rouge, and rubbed with Spanish chalk. The
foils are so smooth upon the glass side that when dry they can be
detached without much difficulty. If both sides are required to be
smooth, the foils are dried between two glass plates. In many respects
their manufacture resembles that of “Gelatine Veneers.”

Gelatine foils are used for printing sacred images, visiting cards,
labels, in the manufacture of fancy articles, artificial flowers, etc.

For the manufacture of artificial flowers very soft and flexible sheets
are made by adding ½ part of glycerine to 1 part of gelatine and mixing
intimately in dissolving the gelatine.

Such gelatine sheets brushed over in addition with Peruvian balsam can
also be advantageously used for tying up wounds instead of gutta-percha
cloth which tears easily and rots soon. They form an air-tight bandage
which clings closely to the parts of the body, and beside the glycerine
contained in them exerts a beneficial cooling effect and acts as an
antiseptic.

_Gelatine Veneers._

Franchi, as far back as 1814, prepared artificial ivory by mixing
gelatine solution with earthy substances. This idea has been again
taken up in modern times for the manufacture of veneers imitating
not only ivory, but also avanturin, lapis lazuli, malachite,
mother-of-pearl, and tortoise shell. These imitations are much liked by
manufacturers of fancy articles, workers in leather, cabinet-makers,
etc. They are prepared as follows:—

The process may be divided into five principal operations: 1.
Preparation of the glass and marble plates; 2. Preparation of the
glue solutions; 3. Pouring the colored solutions upon the plates; 4.
Transferring the layer of glue to the layer of gelatine; and 5. Drying
the veneers and detaching them from the plates.

1. _Preparation of the plates._ Both marble and glass plates are used
for imitations of marble, but glass plates only for imitations of
mother-of-pearl. The glass plates must be ground, but need not exceed
O.11 to O.15 in. in thickness, and only require careful washing and
drying for imitations of mother-of-pearl. For imitations of marble
they should be rubbed with an oiled linen rag. Other glass plates,
after being washed and polished with elutriated rouge and water, are
wiped with a soft rag to remove any particle of the polishing powder.
The polished surface is then gently rubbed with a rag dipped in pure
Spanish chalk, and the excess of chalk carefully dusted off.

2. _Preparation of the glue solutions._ For one dozen plates, each 10¾
square feet, soak 2 lbs. of good, colorless glue in water for 24 hours,
pour off the water and melt the glue in a water-bath and stir in 3½
ozs. of glycerine. For imitating marbles of two colors, compound 20 to
24 fluidounces of this glue solution with the quantities of thoroughly
ground mineral colors given below; the rest of the glue solution is
mixed with 6.34 ozs. of zinc white ground very fine. For imitating
marble of three colors mix 14 fluidounces of the glue solution with
one of the coloring matters and 14 fluidounces with the other coloring
matter, and the remainder with zinc white. For imitating marble with
four colors, take 10 fluidounces of the glue solution to each of the
three coloring matters, and mix the rest with 4½ ozs. of zinc white.

The proportions by weight of the mixtures for 10 different varieties of
imitations of marble and enamel are as follows:—

_a._ Mix 20 fluidounces of the glue solution with 1¾ ozs. of rouge and
2½ ozs. of zinc white, and the rest of the glue solution with 6⅓ ozs.
of zinc white.

_b._ Mix 20 fluidounces of the glue solution with 1¾ ozs. of rouge, and
the rest of the glue solution with 5¼ ozs. of zinc white.

_c._ Mix 14 fluidounces of the glue solution with 1¼ ozs. of zinc white
and 1 oz. of rouge, 14 fluidounces of the glue solution with 1 oz. of
yellow ochre, and the rest with 5¼ ozs. of zinc white.

_d._ Mix 14 fluidounces of the glue solution with 1 oz. of rouge, 14
fluidounces of the glue solution with ¾ oz. of sepia, and the rest with
5¼ ozs. of zinc white.

_e._ Compound 20⅓ fluidounces of the glue solution with 1 oz. of quite
concentrated and filtered solution of aniline black, and the rest with
6⅓ ozs. of zinc white.

_f._ Mix 10 ozs. of the glue solution with 0.8 oz. of rouge, 10
fluidounces of the glue solution with 0.8 oz. of yellow ochre, 10
fluidounces of the glue solution with 0.8 oz. of sepia, and the rest
with 4¼ ozs. of zinc white.

_g._ Mix 20.3 fluidounces of the glue solution with 1.41 ozs. of
lampblack. For gray add sufficient zinc white to produce the desired
shade. The rest of the glue solution is mixed with 6⅓ ozs. of zinc
white.

_h._ Mix 10 fluidounces of the glue solution with 0.8 oz. of umber, 10
fluidounces of the glue solution with 0.8 oz. of bole, 10 fluidounces
of the glue solution with 0.8 oz. of ochre, and the rest with 4½ ozs.
of zinc white.

_i._ _For enamels_ mix 20.3 fluidounces of the glue solution with 1 oz.
of ultramarine, and the rest with 6⅓ ozs. of zinc white.

_k._ Mix 20.3 fluidounces of the glue solution with 1.41 ozs. of chrome
green, and the rest with 6⅓ ozs. of zinc white.

For imitating mother-of-pearl veneers, 0.42 oz. of silver bronze, which
need not be genuine, is ground with a little glue solution or water and
intimately mixed with the above solution of glue. The bronze powder
must not be in a dry state when stirred into the glue, as lumps would
be formed and the veneers become spotted. In place of bronze, essence
of fish scales, which is of course far more costly, can be used.[2] The
glue solution thus prepared is then compounded with different aniline
colors according to the tint desired.

[2] This preparation is also known by the name _Essence d’Orient_. The
material for its production is furnished by a small white fish very
common in the rivers of continental Europe. It accompanies the scales
of this fish, and is detached when the scales are triturated for a
considerable time and thrown into a vessel of water. To collect the
essence the water is poured off upon a fine hair sieve, which retains
the scales and allows the water and the product sought to pass through.
The latter sinks to the bottom, and is obtained pure by decanting the
water. A little ammonia is added to prevent decomposition.

_a._ For yellowish veneers no coloring matter is required, or the
desired shade is obtained by an addition of some solution of picric
acid.

_b._ For colorless veneers or those of slightly reddish tints a smaller
or greater number of drops of a concentrated solution of fuchsine are
added in order to counteract the yellowish color of the glue solution.
For these imitations of mother-of-pearl veneers, concentrated solution
of gelatine compound with 15 per cent. of glycerine can be employed,
especially when essence of fish scales is used.

_c._ For _blue_, the glue solution is compounded with _bleu de Lyons_,
care being had not to use too much, as otherwise the imitation becomes
indistinct. The proper degree of coloring is tested by allowing a few
drops of the colored glue solution to fall upon a glass plate.

_d._ For _red_, solution of fuchsine or carmine is used, the latter
being obtained by dissolving commercial carmine powder in alcohol.

_e._ _Orange colors_ are produced by an addition of solution of
_chrysaniline_ generally sold under the name of Victoria orange, and
_violet_ by adding aniline violet. For these, as well as for the
solution colored with fuchsine, the plates must _not_ be rubbed with
oil, as even the smallest trace of the latter discolors these colors in
drying, or at least the veneers will show spots without color.

3. _Pouring the colored solutions of glue upon the plates._ For
imitations of marble and enamel, the glass plates, after rubbing with
oil, are placed, rubbed surface up, in a perfectly level position.
The proper portion of the white ground-mass, after becoming somewhat
thickish, is then poured upon the plates, and the gaps left free in
pouring filled in and smoothed with a knife-shaped tool of horn or
bone. Upon this white ground the respective colored glue solutions
are then poured in a zigzag form, and in conformity with the desired
design, drawn through the ground-mass with a glass rod. If several
differently colored glue solutions are to be applied, as given, for
instance, under 2_f_, they should be poured in quick succession, so
that the succeeding color runs into the preceding, and a white strip
or spot remains between each color. The whole is then intermingled
by the glass rod, according to the design. If the latter is to have
sharply defined lines and spots, the respective colored solution of
glue is used somewhat thicker, but if, on the other hand, the design is
to be somewhat blended, the glue solutions are used somewhat warmer,
and consequently more thinly fluid. After solidification of the glue
solutions the plates are placed in a cool room for two or three hours.

Imitations of malachite are prepared in a similar manner. Four glue
solutions of different shades of green from the darkest to the lightest
tint are prepared and poured upon a slightly greenish ground, so as
to imitate the characteristic curves and veins of malachite, which
are then further traced with a comb with teeth standing at unequal
distances from each other.

The glass plates set aside to be used for imitation of mother-of-pearl
are now taken in hand. The solutions of glue are kept warm over a water
bath and thoroughly stirred every time before pouring them upon the
plates. The formation of a film on the surface of the glue solution
must be strictly avoided.

For pouring out the solutions it is best to use a porcelain vessel
provided with a spout and handle, and having a capacity of about 6¾
fluidounces. The portion of glue solution required for each plate
(1¾ flu. oz.) is then measured into one of the porcelain vessels,
and, after standing a short time, poured upon the plate and uniformly
distributed. The production of a mother-of-pearl design requires some
skill and practice. A comb with teeth set ½ inch apart is used. It is
held in a somewhat oblique position, the teeth are gently pressed upon
the glass plate, and, with frequent turnings of the comb at a right
angle, cycloidal motions executed. The operation is carried on from the
front to the back edge of the glass plate, and when the glue begins to
thicken on the edges, continued at the softer places until the desired
design is produced, care being had not to touch places which have
already acquired a certain degree of solidity, as this would mar the
pattern. After treating all the plates in this manner, they are set
aside in a cool room for two or three hours.

4. _Transferring the layer of glue to a layer of gelatine._ For each
dozen of veneers soak 2½ ozs. of gelatine, and then melt them in a
water-bath, and after adding glycerine equal to 10 per cent. of the dry
gelatine, let the mixture settle.

The glass plates treated with rouge and Spanish chalk are now placed in
a perfectly level position, and after pouring 5½ fl. ozs. of gelatine
solution upon each of them, the gaps left in pouring are filled in
and smoothed with the glass rod. The front edge of a plate covered
with a colored layer of glue is now, glue side down, placed upon the
front edge of a gelatine plate, while the back edge of the former is
gradually lowered until the glue plate lies firmly upon the gelatine
plate.

It may here be remarked that the gelatine solution must only be allowed
to cool off sufficiently to prevent the melting of the glue plate on
touching it. If it is cooler the veneers will have blisters. It must
further be looked to that, before placing the first plate upon the
gelatine plate, no gelatine escapes, and that any excess only runs off
after the back edge of the glue plate touches that of the gelatine
plate.

The plates are now allowed to rest quietly until the gelatine is
congealed, when they are removed to a cool place where they remain five
or six hours.

Imitations of mother-of-pearl are treated in the same manner with the
exception that the gelatine solution is colored with the same coloring
matter as the glue solution. For colorless or yellowish veneers the
gelatine solution is not colored.

After six hours the first glass plate is detached from the layer of
glue by loosening the latter around the edges with a knife blade, and
the plate gradually lifted off commencing at one corner. With some care
and skill, this operation is readily accomplished without detaching the
gelatine mass.

5. _Drying and detaching the veneers._ The veneers with the gelatine
layer still adhering to the glass plate are now dried. This is done
in a heated room in which the veneers are arranged upon frames so
that they stand almost perpendicular. The hot air for heating the
room enters near the ceiling while the moist air is drawn away near
the floor. The temperature of the lower zone where the fresh plates
are placed should not exceed 68° F. The plates are moved up higher
every day until, on the third or fourth day, they have become entirely
dry. Before removing the veneers from the drying-room they should be
tested in regard to their dryness. They are sufficiently dry, when, on
pressing the finger nail upon the glue, no impression is made.

After removal from the drying-room the plates are allowed to cool off
for at least two hours before detaching the veneers. The operation
begins by detaching the gelatine layer on the edges with a very thin
knife blade. The operator then takes hold of one corner of the veneer
and draws it gradually and carefully from the glass plate. After
trimming the edges the veneers are ready for use.

If the veneers are required to resist the action of water, mix with the
solution of gelatine compounded with glycerine ⅓ fl. oz. of a solution
of 5 parts of chrome-alum in 100 of water to every plate, and immerse
the veneers for a short time after they have been detached from the
first plate, in a similar solution of chrome-alum.

Veneers prepared by these methods can be used for various purposes in
architecture and in the manufacture of furniture. Tennessee and other
marbles have been so closely imitated, that when used for table plates,
etc., the fact of their being imitations could only be detected by the
closest scrutiny. The veneers are also much used for fancy and inlaid
work, for coating columns, etc. To prevent their blistering and coming
off, it is recommended to add one-quarter of its weight of glycerine to
the glue with which they are to be attached to the articles.

_Formo-Gelatine._

This product is used as a dressing in surgery, and, according to
Samuel Rideal, is obtained as follows: Gelatine in aqueous solution is
precipitated by formaldehyde H.COH, or CH_{2}O, as a substance which on
drying is a white powder, neutral, inodorous, and insoluble in water
and dilute chemical agents. In commerce formaldehyde is met with in
aqueous solution as “formalin” containing 40 per cent. of formaldehyde.
If 1 Cc. of formalin be added to 200 Cc. of a 5 per cent. gelatine
solution, the latter is changed into a gelatinous mass, not melted by
heat nor reduced by water. If a smaller quantity of the formalin is
added (1 in 1000; the jelly is said to be meltable, but with a higher
tenacity) when dried it becomes insoluble in warm water. Formalin in
less proportion, though it does not prevent the dried gelatine from
dissolving in warm water, is said to improve the “body” of the jelly
and its keeping qualities, and also the tenacity of the glue. The
results of investigation show that with up to 1 per cent. of formalin
the solidity of the jelly increases; above that it declines. Up to
0.02 per cent. (1 in 5,000) it redissolves in water after drying.
Even with this small proportion the firmness of the jelly is sensibly
increased. The English patent, 4,696, 1894, claims the addition of
formalin during the manufacture of size and glue in such proportion
that the product shall liquefy in warm water.

In examining commercial sheet gelatines for printers’ and photographic
use, they were often found to contain small quantities of formalin.
It seems to improve the quality, a very small percentage increasing
the tenacity, flexibility and keeping qualities, while not affecting
the transparency or rendering the material acid. When applied to
articles that may be used as food, a strength of 1 in 50,000 in the
final prepared product is not injurious to health, but should not be
exceeded. (Rideal and Foulerton, _Public Health_, May, 1899, p. 568.)

Zimmermann applies dilute formaldehyde mixed with glycerine, vaseline,
oil or yolks of eggs, with or without flour, to the surface of
photographic films which are claimed to be thereby rendered more
pliable and not so hard as when the formalin is applied by itself.

It will be seen that formaldehyde in more than traces renders gelatine
insoluble; the product, moreover, is almost unaffected by water, is
more or less hard and elastic and, owing to the antiseptic properties
of the formaldehyde is nearly imperishable.

_Use of Gelatine in Bacteriology._

Gelatine fit for this purpose must be clear and bright, fairly neutral
and of high gelatinizing power. For bacteriological purposes a 10 to 20
per cent. solution of gelatine in sheets or strips is made with meat
broth, and this nutrient jelly, which is obtained by clarification with
albumen perfectly clear and bright, forms a most useful medium for the
cultivation of micro-organisms.

_Artificial Silk from Gelatine._

For the production of textile threads, Millar utilizes the property of
gelatine solution mixed with potassium dichromate, becoming insoluble
on exposure to light. For this purpose a clear solution of gelatine is
mixed with solution of potassium dichromate in the proportion of 100
parts of gelatine to 2 or 2½ parts of potassium dichromate. The fluid
should be of such a consistency as to allow of its being drawn out into
fine threads which on exposure to light become insoluble. Silk woven
from such threads is equal in appearance to the genuine article but of
course is not so strong. It is affected by moisture, becoming limp, but
regains its normal strength when dry.[3]

[3] For further information on this interesting subject, the reader is
referred to “Cellulose and Cellulose Products.” By Dr. Joseph Bersch.
Henry Carey Baird & Co., Philadelphia, 1904.

CHAPTER X.

ISINGLASS AND ITS SUBSTITUTES.

Isinglass is obtained from the air-bladder or sound, as it is sometimes
termed, of different kinds of fishes, especially of the sturgeon,
species _Acipenser_. It is used for culinary purposes, fining beer and
other liquids, for making court-plaster and stiffening silk, though a
good quality of gelatine is practically equal to it for these purposes.
A good quality of isinglass should be pure white, semi-transparent,
dry and horny in texture, and free from odor. It should dissolve in
water of 95° to 122° F., without leaving any residue, and, on cooling,
should yield an almost colorless jelly. From gelatine imitations it
is distinguished by soaking it in warm water and examining under
the microscope, when true isinglass will show a net-work of long,
curling fibres, while gelatine will be simply hyaline. Isinglass is
often imitated with the intestinal membranes of the calf and of the
sheep. This spurious article may be readily recognized because it does
not exhibit, like isinglass, a sort of shining appearance when held
before the eye and daylight, and because, although inodorous, it has
a saltish flavor. If it be torn asunder it will be observed that it
may be rent in all directions, while true isinglass cannot be divided
otherwise than in the direction of its fibres. If a piece of artificial
isinglass be macerated in water it swells, but instead of retaining
its shape as is the case with the genuine article, it becomes divided
into several pieces, forming a sort of curdy precipitate; and if
treated with boiling water, about one-third of its weight is left in an
insoluble state, and the liquor does not form a good jelly. Isinglass
is frequently adulterated with gelatine, which is inserted between the
leaves and rolled up with it. The best indication of this adulteration
is the amount of ash; isinglass yields only 0.9 per cent., while
gelatine yields 4 per cent., and adulterated isinglass 1.5 per cent. or
more.

1. _Russian isinglass._ Russia produces the best and most isinglass.
It is chiefly obtained from several varieties of sturgeon, species
_Acipenser_, which inhabit the Caspian and Black Seas, and their
tributary rivers. The _Acipenser Gueldenstaedtii_, Br. yields the
finest, best and whitest isinglass. It is known by the name of
_Patriarch_, and consists of small horseshoe-shaped pieces rolled
tightly together. It is quite scarce and expensive. When the bladder is
merely dried in sheets, it constitutes _leaf isinglass_. When several
bladders are put together and folded before they are completely dry,
they form _book isinglass_. Each bladder may also be rolled up and
folded around a few pegs in the form of a horseshoe, heart, or lyre, in
which shape it is dried. The latter is the _staple isinglass_, which,
according to its dimensions, is again divided into _long and short
staple_.

Long staple isinglass of fine quality is produced in the Oural. It is
imported in loose leaves, and at times it is twisted like ropes, this
kind being preferred, as it is inferior in quality only to Patriarch.

_Siberian_ purse isinglass is of moderately good quality and is in
general demand. A small kind of strings in a necklace form is sometimes
imported.

A very good sort of Russian isinglass comes into commerce in leaves
and books, and is known by the name of _Samovey_ leaf. It is obtained,
according to the statements of Russian merchants, from the common
sheath-fish (_Siluris Glanis_). The pieces are as large as a hand,
of the thickness of pasteboard, very solid, not very flexible and
of a white-yellowish color. It is inferior in quality to Astrakhan
isinglass, which is one of the best kinds.

In _Russia_ the isinglass is generally prepared by boys under the
supervision of elder experts. The swimming bladder is first placed in
water and left there for some days with frequent changes of the water
and removal of all fatty and bloody particles. The warmer the water
the more rapidly the operation is completed. The bladders are finally
removed and cut longitudinally into sheets which are exposed to the
sun and air, being laid out to dry, with the outer face turned down,
upon boards of linden or bass wood. The inner face is pure isinglass,
which, when well dried, can with care be removed from the external
lamellæ. The finer sheets thus obtained are placed between cloths to
protect them from the flies, and are then subjected to a heavy pressure
so as to flatten them out and render them uniform. After this they
are assorted and tied up in packages. The packages composed of the
isinglass of the large sturgeon usually contain from ten to fifteen
sheets and weigh a pound and a quarter; those of the other contain
twenty-five sheets weighing a pound. Eighty of these packages are
usually sewed up in a cloth bag, or sometimes inclosed in sheet lead.

The outer lamellæ of the air-bladder, after the isinglass has been
removed, also contain a considerable quantity of glue which, when
softened in water, is scraped off with a knife and moulded into little
tablets of about the size of a silver dollar, and then dried.

2. _North American or New York Isinglass._ It is in thin strips
several feet long but ½ to 1½ inch wide. It is less soluble than
Russian isinglass, and yields frequently a dark-colored solution. It
is prepared, according to Dr. J. V. C. Smith’s statements, from the
air-bladder of the common hake (_Gadus merluccius_), which is macerated
in water for a short time, cut open and subjected to pressure between
iron rollers, by which it is elongated to the extent of half a yard
or more. It is then carefully dried, packed and sent to market. The
air-bladder of the common cod (_Gadus morrhua_) is prepared in a
similar manner, but yields a poorer kind of isinglass.

3. _East India Isinglass._ It would seem that for a long time this
has been exported from _Calcutta_ to _China_, but has only lately
attracted the attention of European dealers. It is prepared from the
air-bladder of the _Polynemus plebejus_, and comes into commerce either
in the form of leaves or purses which seem to consist of the unopened
air-bladder. East Indian isinglass has a disagreeable fish odor, due
very likely to careless preparation, which makes its use impossible for
many purposes, and, of course, depreciates its commercial value. The
oval-oblong purses are about nine inches long, three and a half inches
wide, weigh about 7 ozs. and have a dark-yellow color. East India leaf
isinglass, _i. e._, the opened and dried air-bladder, consists of
yellowish-colored leaves eight to nine inches long, six to seven inches
wide, and about three-tenths of an inch thick. The leaves are sometimes
rolled out into long ribbons about one-tenth of an inch thick, the
surface of which is covered in places with a thin film of lime.

What is known as picked East India isinglass is brought into commerce
in small shreds about two to three inches long, and tapering at the
extremities.

A variety of isinglass very white and pure and scarcely inferior to
Samovey leaf is brought from Manila. The fish which yields it is caught
on the coast of the Philippine Islands, especially at Luzon.

4. _Hudson Bay Isinglass._ It is brought into commerce in the purse
form. Some specimens measure twelve inches in length and three and
a half inches in diameter, and weigh one and a half ounces. It is
of light-yellow color, nearly transparent, without odor or taste.
The inner lining of the sac, which can be readily stripped off, is
insoluble in water, while the remaining portion dissolves to a slightly
colored jelly. We have been unable to ascertain from what species of
fish this isinglass is procured.

5. _Brazilian Isinglass._ This is imported from _Para_ and _Maranham_,
and is also called _Cayenne_ isinglass. For a long time there existed
a doubt from what species of fish this isinglass was procured, but it
is now settled that it is prepared from the air-bladder of _Silurus
Parkerii_, a fish which is frequently found in the muddy waters of the
rivers in the province of Grao Para, where these waters mingle with the
sea.

_Brazilian_ isinglass comes in the form of pipe, lump and honeycomb.
On account of its dark color it is not in much demand for ordinary
use, but is frequently employed in England for clarifying glue. When
digested in water it leaves much insoluble substance behind, being in
this respect also inferior to Russian isinglass.

6. _German Isinglass._ Under this name we may mention the mucous
membrane of the sturgeon (_Acipenser sturio_), prepared in Hamburg.
When boiled with water it leaves 16 per cent. of insoluble substance.

It is said that an excellent isinglass can be made from the scales of
shad and herring, which are first freed from their silvery coating.
This may furnish a useful hint to persons who are near some of the
great fishery establishments of the country, at _Gloucester, N. J._,
and _Alexandria, Va._, for instance, where thousands of shad are scaled
and salted every year.

To give inferior qualities of isinglass a better appearance and make
them more salable, they are frequently bleached with sulphurous acid.

_Ichthyocolle Française._ Under this name, Rohan has introduced a
substitute for isinglass. The material used for its manufacture is
blood fibrin, which, after washing in running water, is thoroughly
kneaded and, after draining, digested at 59° F. with dilute sulphuric
acid of 8° to 10° Bé. for eight days, after which the mass is freed
from acid by washing in running water.

The fibrin freed from acid becomes transparent and gelatinous by
treating with weak soda lye of 3° to 4° Bé. at 59° F., whereby it
swells up and increases hourly in volume. After twenty-four hours
it is taken from the soda lye, and after removing the free soda by
washing, heated to 212° F, in a water-bath. The fibrin dissolves and
becomes so thinly fluid that it can be filtered. 75 to 80 per cent. of
the water is then evaporated, and the fibrin thus prepared can be used
as a substitute for isinglass for fining purposes. Ichthyocolla swells
more quickly in cold water than isinglass; 15 to 20 per cent. divided
in water forms a thickly fluid substance, which on heating dissolves to
a perfectly clear fluid. For fining beer with ichthyocolla add 2 to 10
per cent. of pure tannin, which does not injure its power of dissolving.

_Isinglassine._ Under this name is known an isinglass substitute
prepared from the gelatinous material from calves’ feet and other
sources. The material is reduced by machinery to a pliable homogeneous
mass, rolled out into sheets, dried, pressed and shredded.

_Chinese isinglass_ is identical with the _Japanese Agar-Agar_, and is
obtained by cleansing and boiling certain species of algae found in
Chinese and Japanese waters. This isinglass, or gelatine, possesses the
following properties:

Placed in cold water it softens without dissolving like gelatine, and
forms a structureless tubular mass which is not sticky. By boiling,
it dissolves more readily than isinglass, but with greater difficulty
than gelatine. A 1 to 2 per cent. solution is easily filtered through
paper or linen, and when cold forms a solid jelly clear as water and
without taste or odor. Jelly prepared with one-half per cent. of
Chinese gelatine is more solid than one prepared with 4 per cent. of
French white gelatine, retains its consistency longer, and will stand a
temperature of 86° to 122° F. before becoming liquid. Used for jellies,
or mixed with other foods, it does not impart to them a glue taste
never wanting in bone gelatine. When decomposed by long standing, it
does not acquire a disagreeable odor, while decomposed isinglass or
gelatine exhales a putrid smell.

Agar-Agar contains, according to analyses: Cellulose, starch, gum,
dextrine, vegetable mucus, vegetable wax, resin, chlorophyll, albumen,
a peculiar acid, and several mineral substances.

_Irish moss_ (_Chondrus crispus_) which grows on rocks of the American
and European shores of the Atlantic Ocean, yields a jelly which has
been employed as a substitute for isinglass, as a size, for thickening
colors in calico printing, and in stiffening silk. In a fresh or
softened state the plant is cartilaginous, of a brownish or purple, or
frequently yellow or green color. After washing in water and drying in
the sun it turns whitish or yellowish, and becomes somewhat translucent
and of a horny appearance. It has a slight seaweed-like odor and a
mucilaginous, somewhat saline taste. One part of it boiled with 20
parts of water gelatinizes on cooling.

_Fish Glue._

This product, which is prepared in many localities from fishes, must
not be confounded with isinglass, though the purer varieties may serve
as substitutes for the latter or for gelatine.

Jennings gives the following process for the preparation of fish glue.
The fishes are treated with dilute sulphuric acid until the skin can
be detached. The acid water is then drained off and replaced by milk
of lime to neutralize adhering sulphuric acid as well as to saponify
the fat. The milk of lime is several times drained off and renewed, the
mass thoroughly washed, cut up in a hollander and treated cold with
solution of sodium hyposulphite, common salt and alum. After a few days
the liquor is drawn off and replaced by a mixture of alum solution,
dilute sulphuric acid and nitric acid in which the mass is allowed
to remain for a few days. Fishes with dark skins are treated with a
mixture of hydrochloric and sulphuric acids. After washing, the skin
is removed and the fibres which have become detached from the bones
are separated by digestion in dilute solution of mercuric chloride and
alum. Adhering fatty parts are removed with warm milk of lime, the lime
is neutralized with hydrochloric acid, and the mass boiled with water
for the formation of glue. The resulting glue-liquor is clarified with
sulphurous acid and alum, and when all the impurities have subsided,
compounded with acid sodium carbonate till all the acid is neutralized.
The finished solution is concentrated so that it gelatinizes on cooling
and can be cut in cakes which are dried in the usual manner.

Fish scales, especially those of carps, are treated in a similar
manner. The bone-earth is extracted with hydrochloric acid, the
extracted material thoroughly washed, and then boiled in soft water
till it can be readily stirred. The liquor is drawn off from the horny
sediment, clarified with alum, evaporated, and after all the impurities
have subsided, poured into moulds and treated like ordinary glue.

Considerable quantities of fish glue are produced on the Norwegian
coast from waste obtained in the preparation of codfish. The fish when
caught are cut open and the air-bladders removed, which are dried and
brought into commerce as isinglass. The head is then cut off and the
bones detached in one piece. The flesh is dried in the air, and forms
the codfish of commerce. The heads and bones are first treated with
hydrochloric acid or directly boiled under slight pressure in water,
and the resulting liquor concentrated so that it will gelatinize.

A substitute for isinglass, also for gelatine and glue, is prepared by
C. A. Sahlströhm, of Stockholm, according to his patent, from fish and
fish waste by treatment with bleaching powder, potassium permanganate,
and nitrous and sulphurous gases.

For this purpose the fishes, or portions of fishes, are first well
washed in fresh water and then left for from three to four hours in a
solution of bleaching powder (in the proportion of 2 lbs. of bleaching
powder to 300 quarts of water). After washing they are treated for
about 30 minutes with a solution of potassium permanganate (in the
proportion of 1¾ ozs. of potassium permanganate to 250 or 300 quarts of
water), and then exposed to the action of the nitrous gas, produced by
heating 10 to 15 ozs. of nitric acid for every 88 lbs. of raw material.
This gas may be first absorbed by water, as in the manufacture of
sugar, or sulphur dioxide may be used instead of nitrous gas. The
former would be obtained by burning about 7 ozs. of sulphur for every
88 lbs. of raw material.

The material, after this treatment, is washed. Those portions intended
for the production of isinglass substitute are freed from their outer
skins and dried and pressed at a gentle heat. The portions destined to
produce gelatine or glue are, on the contrary, exposed to a temperature
of from 104° to 122° F. for from ten to twelve hours, by which the
material is mainly dissolved. The mass is then forced through a
strainer or sieve, and the liquor allowed to gelatinize by standing for
some hours. The jelly is finally dried, as is usual in the manufacture
of glue or gelatine.

_Whale glue_ is, according to Culmann, obtained in the Russian island
Jeretike from the liquor remaining in the boilers after the extraction
of the oil by means of superheated steam. By reason of the raw and
moist atmosphere which prevails in that locality, even in summer,
drying the glue is not practicable, and for this reason it is brought
into commerce in the form of a compact jelly mixed with a preservative
and packed in tin boxes. The commercial article contains 41.65 per
cent. water. It is liquefied by placing the can in boiling water, and
melts at 176° F. As shown by mechanical tests, it possesses great
tenacity, and two pieces of wood glued together lengthwise cannot be
separated at the joint but break alongside of it.

CHAPTER XI.

TESTING GLUE AND GELATINE.

It is of importance that the manufacturer as well as the dealer should
know how to test the quality of a glue. This may be done by chemical
means and in a mechanical way.

_Determination of moisture._ For this purpose a weighed quantity
of the sample, finely powdered, is for fourteen hours exposed to a
temperature of 217° to 230° F. It is then cooled under the dessicator
and reweighed. The content of moisture is then calculated from the loss
in weight.

_Determination of ash._ The origin of a sample of glue may be traced
by examining the ash for phosphates of lime and magnesia, bone-glue
containing both, while skin-glue is free from phosphates. Reduce
a portion of the sample to a fine powder, and weigh it in a tared
constant crucible. Heat slowly over a Bunsen flame until carbonized,
then remove the crucible to the muffle, and heat to bright redness for
10 hours. Cool under the dessicator and weigh. The increase in weight
of the crucible is the ash of the sample. This will vary from 1 to 2
per cent. in a gelatine, 2 to 3 per cent. in a good glue, 6 to 8 per
cent. in a common quality.

_Determination of Acidity._ Kissling elsewhere determines the acidity
by suspending 30 grammes of the sample in 80 Cc. of cold water for 10
to 12 hours in a flask connected with a condenser. The volatile acids
are then driven over by a current of steam into a graduated cylinder.
When the distillate amounts to 200 Cc., distillation is interrupted,
and the distillate treated with standard decinormal alkali. When the
distillate contains sulphurous acid, a known quantity of the standard
alkali is previously added to the cylinder.

An undue quantity of acid may be detected by the taste. Glues may be
alkaline from the addition of excess of lime in the manufacture to
correct the sourness of the jelly. For uses where colors are concerned
the glue must be neutral to litmus; for adhesive uses this does not
matter unless the alkalinity or acidity is due to defective preparation
(Samuel Rideal).

_Determination of Glutin._ The percentage of glutin in a glue solution
is determined by precipitating it with tannin. The dense white
precipitate formed is thrown on to a tared filter, washed with hot
water, dried and weighed. The calculation is made on the basis that the
tannate of glutin has a percentage composition of 42.74 per cent. of
glutin and 57.26 per cent. of tannin.

Bisler-Beumat while employing the same principle prepares two
solutions: _a._ 10 grammes of pure tannin to the liter. _b._ 10 grammes
of pure isinglass and 20 grammes of alum to the liter. The ratio in
which the tannin is precipitated by the isinglass solution, which
Risler considers as pure glutin, is then determined by titration. The
tannin solution is then diluted so that exactly an equal volume of glue
solution is precipitated by it.

In order to test a sample of glue, dissolve 10 grammes of it together
with 20 grammes of alum in a liter of water, heat being applied if
necessary. Next 10 cubic centimeters of the tannin solution are taken
to which an equal bulk of glue solution is at once added, as one may be
sure that this quantity is not sufficient for the precipitation of the
measured quantity of tannin, because no glue found in commerce is as
pure as isinglass. The vessel containing the mixed liquids being well
shaken and the precipitate having subsided, another cubic centimeter of
glue solution is added to the tannin solution which is next filtered
through a moist cotton filter. If _one_ drop of the glue solution still
produces a precipitate in the clear filtrate, another cubic centimeter
is added to the tannin solution, and then again filtered, these
operations being repeated until the filtrate is no longer rendered
turbid by the glue solution.

With the known relation of the tannin solution to pure glue
(isinglass), a conclusion may be formed from the number of cubic
centimeters of glue solution used as to the content of glutin in the
sample examined.

The percentage of glutin varies, of course, according to the quality
and origin of the glue. Bone glue of good quality contains from 50 to
52 per cent. and skin glue from 65 to 75 per cent.

S. Dana Hayes analyzed two samples of American glue of best quality and
obtained the following results:

a. b.
Water (escaping at 212° F.) 16.70 16.28
Glue substance 79.85 80.42
Calcium carbonate 1.42 1.33
Calcium sulphate 0.41 0.34
Magnesium phosphate 0.35 0.31
Alkaline salts 0.17 0.12
Silica, ferric oxide, etc. 0.09 0.08
Zinc oxide 1.01 1.12

The chemical modes of testing glue give only the quantity of glutin
contained in it, but do not prove that the substance combined with
tannin corresponds to the actual adhesive power of the glue, for it is
possible that a glue containing a large quantity of glutin may possess
but little adhesive power, and a jelly from which the glue is formed
may contain an equal amount of glutin with the latter, but not possess
an equal power of adhesion.

It is certain that the determination of the glutin alone is not a
criterion of the quality of glue. In the absence of a reliable method
of direct analysis, attempts have been made to deduce the quality of
glue from indirect properties.

One of these methods consists in immersing the sample of glue in a
large quantity of water at 59° F. for a considerable time. The glue
swells up, absorbing 5 to 16 times its own weight of water. The
more consistent and elastic the glue in this state is found to be,
the greater its adhesive power, and the larger the quantity of water
absorbed the more economical the glue will be in use. This method does
not give thoroughly reliable results, and should only be employed with
bone-glue, as skin-glue does not behave in a similar manner.

[Illustration: FIG. 65.]

A more reliable method is to test the strength of a glue by the method
first proposed by Lipowitz, which is based on the weight-sustaining
power of a jelly of known strength and temperature. The test is
executed as follows: Soak 5 parts of the sample in water, then dissolve
it in sufficient hot water to make the weight of the solution equal
to 50 parts, and allow to stand for 12 hours at 64.4° F. in a glass
cylinder of uniform width to gelatinize. Cover the glass cylinder with
a tin cap perforated in the centre, Fig. 65. Through the perforation
is passed freely a stout iron wire, at the lower end of which is
soldered a piece of tin shaped like a saucer, the convex side of it
resting on the surface of the jelly. To the upper end of the wire,
which together with the tin saucer should weigh 5 grammes, is soldered
a funnel weighing 5 grammes, and capable of holding up to 50 grammes
of fine shot. The apparatus is gradually loaded with shot until the
saucer-shaped piece of tin is forced into the jelly. The greater the
strength of the jelly, the heavier will be the weight required. From
the determined weight of the shot used, the relative value of the glue
as to its adhesive power is determined.

The following results have been obtained by comparative experiments
with this apparatus:

Variety of Glue. Weight required to force
the saucer down.

Breslau 1704 grammes = 3.74 lbs.
Russian 1446 grammes = 3.18 lbs.
Cologne 1215 grammes = 2.67 lbs.
Muhlhausen I. 727 grammes = 1.599 lbs.
Nördlingen 724 grammes = 1.592 lbs.
Muhlhausen II. 387.5 grammes = 0.85 lbs.

The results of these experiments agree to a remarkable degree with the
market prices of the varieties of glue, which is not the case with
glues tested by the methods previously mentioned. The results of these
tests are given in the table below:

Table Key:

Variety of Glue.

1. Best White isinglass in three qualities
2. Translucent yellowish bone glue in tablets and easily soluble
3. Pale yellow glue similar to No. 2
4. Brown-reddish, brittle in fracture and soluble
5. Clear translucent glue of medium brown color
6. Brown-yelow glue in thick tablets and possessing but little
translucency
7. Pale brown-yellow glue, readily soluble and elastic before breaking
8. Pale amber-colored glue with but little translucency
9. Brown glue, solution turbid
10. Amber-colored glue, opalizing and readily soluble
11. Thich tablets or dark-brown glue, solution very turbid
12. Dark horn-like glue with little translucency
13. Very translucent glue of a light brown color and very clean
solution
14. Translucent dark-brown glue, giving a very clear solution

----+----------------+--------------+------+-------------+-------------
|Loss of water | 100 parts |Glutin| Water |A 100 per cent.
|in drying for | of glue are | per | absorbed in |solution of
|several hours at| precipitated |cent. |24 hours by 5|glue will bear
|239° to 248° F. |by tannic acid| |parts of glue|a weight of
----+----------------+--------------+------+-------------+-------------
1. | 20 to 21 | 74.62 | 55.69| — |
| | | | |
2. | 13.2 | 76.2 | 56.8 | 40 |64 grammes
| | | | | (2.25 ozs.)
3. | 13.0 | 70.0 | 52.2 | 35 |60 grammes
| | | | | (2.11 ozs.)
4. | 10.0 | 71.0 | 52.9 | 12 |Does not
| | | | | gelatinize.
5. | 11.0 | 71.5 | 53.3 | 20 |20 grammes
| | | | | (0.705 oz.)
6. | 12.5 | 68.0 | 50.7 | 27 |15 grammes
| | | | | (0.52 oz.)
7. | 13.0 | 66.6 | 49.7 | 30 |36 grammes
| | | | | (1.26 oz.)
8. | 9.5 | 68.5 | 51.1 | 33 |60 grammes
| | | | | (2.11 oz.)
9. | 10.0 | 82.0 | 53.7 | 30 |50 grammes
| | | | | (1.76 oz.)
10.| 9.5 | 73.0 | 54.4 | 35 |56 grammes
| | | | | (1.97 oz.)
11.| 13.5 | 64.0 | 47.7 | 18 |23 grammes
| | | | | (0.81 oz.)
12.| 9.0 | 72.6 | 54.2 | 29 |12 grammes
| | | | | (0.42 oz.)
13.| 13.5 | 70.0 | 52.2 | 30 |40 grammes
| | | | | (1.41 oz.)
14.| 15.0 | 66.0 | 49.4 | 25 |42 grammes
| | | | | (1.48 oz.)
----+----------------+--------------+------+-------------+-------------

This table shows the following facts:

1. The percentage of water in the 14 dry varieties of glue examined
varies between 9.0 and 21. The loss of water from isinglass is
surprisingly large, especially as it cannot be explained by an
artificial admixture of water, since the six varieties examined
reabsorbed the same percentage of water from the air. The percentage of
water in the other varieties of glue differs but little.

2. The various varieties of glue required different quantities of
tannic acid for their precipitation, the amount for 100 parts of glue
varying between 66 parts and 76.2, or calculated to per cent., between
49.4 and 56.8.

3. Placed in cold water, glue swells up and absorbs from 12 to 40 parts
of water. The behavior of the various varieties differs very much in
this respect, and in most of the experiments, with the exception of
variety No. 4, the percentage of glutin is in exact proportion to the
quantity of water absorbed.

4. The strength of the gelatinized glue varies between 12 grammes
(185.18 grains) and 64 grammes (987.67 grains) for a 10 per cent.
solution. This property corresponds neither with the absorption of
water nor the percentage of glutin.

Variety No. 4, in the table, contains 52 per cent. of glutin, but does
not gelatinize, its strength being therefore equal to 0, while variety
No. 14, with 49.4 per cent. of glutin, therefore less than No. 4,
shows a strength of 42. As no close connection between the properties
mentioned in the table can be recognized, it is best not to be guided
by these properties alone, but to test also the behavior of the glue in
practical use. Such test consists in estimating the adhesive power of
the glue from the weight required to tear asunder two pieces of wood
glued together and dried. But as the results obtained by this purely
practical test must necessarily vary on account of the impossibility of
having two surfaces of wood always exactly alike, and the uncertainty
of applying every time the same quantity of glue, Weidenbusch’s method
may here be given. It is based upon the principle that sticks of
plaster of Paris cast of exactly the same material and of uniform size
break under the same weight when placed upon two supports and loaded in
the centre. If now such plaster sticks be saturated with glue solutions
prepared according to the same method, but from different qualities
of glue, a greater force will be required for breaking them, and this
force will be the greater the better the quality of glue is.

The plaster sticks are prepared as follows: Reduce pure crystallized
gypsum to a fine powder, pass the latter through a sieve having 324
meshes per square centimeter and heat it to between 284° and 302° F.
For casting the sticks moulds of soap-stone are used. The moulds are
made by boring in a piece of soap-stone, at a distance of about 1
centimeter from each other, holes with a diameter of 6 millimeters on
top and 7½ millimeters on the bottom.

The gypsum is weighed off in portions of 1 gramme each, mixed with 1
gramme water and cast in the moulds. The solidified sticks are first
dried at a moderate heat and then over calcium chloride, and kept for
use in an air-tight vessel.

[Illustration: FIG. 66.]

The glue solution is prepared as follows: The glue dried at 212° F. is
weighed, soaked over night in water, then melted in a small glass in
the water-bath, and finally enough water is added so that the solution
contains 10 per cent. of dry glue.

The plaster sticks are for one or two minutes immersed in the glue
solution heated to 212° F., and then placed vertically upon a glass
plate until superficially dry, when they are completely dried at 212°
F. It is recommended to color the glue solution with indigo, the
uniform saturation of the sticks being thereby more easily recognized.

The apparatus for testing the strength of the sticks consists of a
brass ring _a_, Fig. 66, having two notches to receive the stick, and
its diameter is divided into two equal parts by an indicator. The ring
is supported by a pin, by means of which it is secured in a stand. The
apparatus is completed by an iron or glass cup which is suspended by
three cords, _i_, and the hook _f_ to the plaster stick _b_. The hook
_f_ is placed in the position indicated by the indicator. Mercury is
now poured into the cup until the plaster stick commences to break. The
weight required is recorded and compared with a standard glue. During
the experiment the cup is suspended by the three cords _h_ to the ring
_a_, and is thus caught when the plaster stick breaks. On the lower end
of the cup is a clip for emptying the mercury into a vessel so that
none of it is lost.

The “Artillery Werkstätte” at Spandau has adopted the severing strain
of two blocks of wood glued together. The test is executed as follows:
Three parts of glue (but not less than 250 grammes) are mixed with
6 parts of water and boiled in a steam bath until the weight of the
boiled glue amounts to only 5/9 of the original mixture. The reason for
this continued boiling is to ascertain whether the glue to be tested
retains the required adhesive power even after six hours continued
heating in a steam bath as frequently happens in the workshop. With the
glue thus prepared the following breaking test is made:

Blocks of hard or soft wood 420 millimeters long and 40 × 40
millimeters cross section are cut in two, so that each piece thus
obtained is 210 millimeters in length. These two pieces are then again
glued together across the grain with the glue to be tested. The
block is then placed in a dry room at a temperature of 62° to 68° F.
for 72 hours, when the joint is tested as to its resisting power. At
a distance of 180 millimeters from the joint a hole is bored in the
block. Through this hole is pushed a bolt furnished on the lower end
with a hook to which a scale is suspended. The block of wood is clamped
to a table so that the joint projects 1 centimeter beyond the edge. The
scale is at the start loaded with 25 kilograms, the load being every
five minutes increased 5 kilograms till fracture takes place.

Two such blocks, one of hard and one of soft wood, are subjected to the
test, and a serviceable glue must stand at least an average load of 70
kilograms.

_Determination of adulterations._ White lead, sulphate of lead, zinc
white, or chalk in quantities varying from 4 to 8 per cent. are
frequently mixed with the melted glue to improve the appearance of the
finished product. Thus, according to analyses by A. Faisst, Russian
glues contained in 100 parts foreign admixtures as follows:

I. II. III. IV.
Zinc white 1.66
Chalk 2.40 2.95 3.79 2.10
Sulphate of lead — 4.16 2.35 3.18
—— —— —— ——
4.06 7.08 6.14 5.28

The so-called patent glue which is opaque and of a white color is
produced by adding considerable quantities of white lead to ordinary
glue.

According to Barreswil, glue is frequently mixed with lead acetate
solution to protect it from putrefaction. Such an addition, as well
as the presence of white lead or sulphate of lead, is detected by the
introduction of sulphuretted hydrogen into very dilute glue solution.
In the presence of lead acetate a black precipitate of lead sulphide
appears in the clear solution; if white lead or lead sulphate is
present, the white powder settling on the bottom is blackened by the
formation of lead sulphide.

For the detection of other earthy additions, prepare a very dilute
solution of the glue in question and allow it to stand quietly for
a few hours. The heavy additions subside, and after decanting the
supernatant fluid is collected upon a small filter and examined by the
customary analytical methods.

It is difficult to say what quantities of earthy constituents actually
constitute an adulteration, since it is claimed by many practical men
that a considerable content of earthy parts is of advantage as regards
the cementing power of glue. Generally speaking it may, however, be
said that a glue containing more than 6 to 8 per cent. of earthy
constituents must be considered adulterated.

For many purposes, especially if the glue comes in contact with colored
materials as, for instance, in book-binding, a content of free acid
would exert an injurious effect upon the colors, destroying or changing
them. It is therefore advisable to test the glue with blue litmus paper
which, in the presence of free acid, is reddened.

In testing a large number of samples of glue, Kissling obtained the
following results:

Number Smallest Largest Average
SKIN GLUE. of samples. percentage. percentage. percentage.

Water 15 13.4 18.1 15.7
Ash 16 1.0 4.13 2.15
Fat 21 0.01 0.090 0.037
Volatile acids, free } 8 {0.084 0.238 0.178
Volatile acids, fixed } {0.084 0.334 0.191

BONE GLUE.

Water 25 11.5 17.7 13.4
Ash 26 1.16 5.07 2.46
Fat 5 0.047 0.217 0.113
Volatile acids, free } 7 {0.088 1.451 0.655
Volatile acids, fixed } {0.097 0.721 0.460

However, those who from their practical knowledge are most competent to
judge the commercial value of a glue, scarcely require such complicated
tests, as by taking the sample in their hand and looking at it,
they can in most cases tell its quality. Great hardness, a clear,
rattling sound when struck, and resistance to breaking are signs of
good quality, and if the cake is cut thick, it shows that the jelly
possessed great consistency. Many kinds of glues are intentionally
cut thin so that they will dry before spoiling. The derivation of
a glue from a sound jelly is recognized by the fine cutting lines.
When the jelly possesses but little gelatinizing power and is in the
first stages of decomposition or putrefaction, or formation of sugar
has already set in, it cannot be poured into moulding boxes, as it
would putrefy before it has a chance to gelatinize. Such sick jelly is
poured in thin layers upon glass or metal plates so that it may acquire
sufficient solidity to allow of its being cut up into leaves and dried
upon nets. If the edges of the glue are deeply indented and raised, the
jelly, before drying, possessed but little concentration (25 to 30 per
cent.), and if notwithstanding this, it acquired sufficient consistency
to allow of its being cut, it must have been very sound. Glues cut
thick and showing no indentations and raised edges, are derived from
excessively concentrated jellies (30-35-40 per cent.). Such jellies
lose in quality in evaporating.

A high degree of transparency is a favorable sign as regards the purity
of a glue, substances inducing putrefaction having been eliminated.
Hence this property should be worthy of recommendation, but the
consumer having been disappointed in the use of thin glass-clear glues,
distrusts also the thick-cut transparent product, preferring a turbid,
translucent or opaque article. For this reason the manufacturer is
forced to render glass-clear glue turbid with coloring matter.

The color of the glue is also a means of judging it. To be sure,
chemically pure glutin is a colorless substance, but glue is always
colored more or less dark brown. Although this coloration does not in
the least impair the adhesive power, the manufacturer endeavors to
produce a product of as light a color as possible, and this is best
effected by bleaching with sulphurous acid. By this means the glue not
only acquires a lighter color, but also becomes more stable, substances
inducing putrefaction being destroyed by the acid.

PART II.

CEMENTS, PASTES, MUCILAGES.

CHAPTER XII.

CLASSIFICATION OF CEMENTS.

The great variety of substances entering into the manufacture of
cements and pastes makes a division of them extremely difficult.
Stohmann divides them into the following groups:

1. _Oil cements._
2. _Resinous cements._
3. _Cements containing rubber or gutta percha._
4. _Cements containing glue, or starch paste._
5. _Lime cements._

Generally speaking, this division is correct; the only change we
would suggest is to apply the term _agglutinant_ or _paste_ to bodies
containing glue and starch paste.

When we attempt a division of the cements according to the bodies to be
cemented, we find that the result will be a larger number of groups;
as we must take into consideration whether the articles to be cemented
have to be heated or not, whether they are to come in contact with
water or other liquids, and other circumstances which would necessitate
modifications in the composition of the cements themselves.

According to this, we might group the cements as follows:

1. _Cements for glass and porcelain, for repairing broken articles,
for fastening glass letters upon show-windows, etc._

2. _Cements for metals not exposed to an increase of temperature, for
instance, for tightening the joints of gas and water pipes._

3. _Cements for stoves and other articles, which have to stand an
increased temperature._

4. _Cements for chemical apparatus, i. e., such as will have to resist
the action of chemical agents._

5. _Cements to protect vessels of glass, porcelain, or metal against
the action of fire._

6. _Cements for filling hollow teeth, for microscopical preparations,
and other delicate articles._

7. _Cements for special purposes, for instance, for cementing
meerschaum, tortoise shell, etc._

_Chemical nature of cements._ The different varieties of cement
frequently contain substances which act chemically upon each other,
or upon the bodies to be united with them. To determine the practical
availability of a variety of cement for a determined purpose, it is of
importance to know the reciprocal behavior of these substances towards
each other, as from this we are able to judge at once whether a cement
is suitable for a certain purpose or not.

_Oil cements._ The fluid fats, commonly called oils—though there are
oils which remain solid at the ordinary temperature, as, for instance,
palm oil and cocoanut oil—may, as regards their behavior on exposure to
the air, be divided into two large groups, namely, drying and nondrying
oils. As samples of these groups may be mentioned olive oil and linseed
oil.

If a thin layer of olive oil protected from dust is exposed to the
air, it will remain fluid for years and retain its characteristic oily
consistency. The only change it undergoes is that it becomes somewhat
more viscid and rancid, and acquires a darker color, but it never dries
up.

Linseed oil treated in the same manner solidifies in the course of a
few weeks to a hard, tough and elastic mass, resembling, as regards its
physical qualities, resin or rubber.

By compounding a drying oil with a small quantity of litharge,
pyrolusite, manganous borate, etc., and heating the admixture to the
boiling-point, it acquires the property of drying in a few hours when
exposed to the air in a thin layer. Oil so treated has been changed to
a varnish.

By bringing a drying oil in contact with a body possessing strong basic
properties a peculiar process takes place; the sebacic acids contained
in the oil combine with the basic bodies to solid combinations which
are insoluble in water, and, on exposure to the air, change gradually
into masses as hard as stone. Such combinations, as regards their
chemical composition, resemble ordinary soap, and for this reason are
called insoluble soaps to distinguish them from ordinary soap which is
soluble in water.

Burned lime, calcined magnesia, whiting, ferric oxide, litharge, and
minium possess the capacity for forming insoluble soaps on coming
in contact with drying oils and, still more quickly, with varnishes
prepared from them.

The hardness of these soaps in time increases considerably by the oil
not saponified drying in. The oil cements are principally used for
tightening water and gas pipes, as they resist the action of water,
steam and gas.

The only drawback connected with these cements is that they must reach
a certain age before becoming entirely hard, and that, on account of
the high price of drying oil or varnish which is absolutely required
for their preparation, they are rather expensive. The ordinary
glazier’s putty and the red lead and linseed-oil cement used in
constructing water and gas conduits belong to this group.

_Resinous cements._ By resins are understood a number of constituents
of plants which exude in thick viscous masses through incisions made
in the trees, and on exposure to air are gradually converted into
less transparent, brittle masses. When heated they melt more or less
readily, forming a thick, ropy liquid, and brought in contact with an
ignited body they burn with a bright flame and much sooty smoke.

By making incisions in the bark of any of the whole genus of _Pinus_
belonging to the _Coniferæ_ family, a viscous mass of a strong odor,
called turpentine, is obtained. It consists of a solution of common
rosin in the essential oil of turpentine, and when distilled yields
from 75 to 90 per cent. of colophony or rosin, which remains in the
retort, and from 25 to 10 per cent. of the essential oil, commonly
called spirits of turpentine. Pure rosin is a brittle, tasteless, and
almost inodorous mass of a light yellow color and a smooth, shining
fracture.

The various resins found in commerce, such as shellac, mastic, elemi,
copal, etc., are formed in a similar manner.

The principal points of importance for our purpose are the different
degrees of hardness and brittleness and the melting-points of the
various resins. While some possess but slight hardness, for instance
elemi, others, such as copal and amber, excel in this respect and their
brittleness and high melting-point.

To decrease the brittleness of resins, essential oils are sometimes
added, or resinous cements are mixed with oil cements or a fat drying
oil, or compounded with rubber cement.

Resinous cements are either softened by heating or entirely melted,
or solutions of resins in volatile solvents are used, which, in
evaporating, leave the resin behind.

The resinous cements possess great power of resistance, and are
therefore well adapted for tightening water and gas pipes, but they
have the disadvantage of not standing a high temperature and possessing
a certain degree of brittleness which renders them unfit for the
cementing of articles exposed to frequent shocks.

Many of these cements, especially those prepared with pitch or
asphaltum, can be produced at a very low cost, and do excellent service
for water-proofing vessels, water-reservoirs, brickwork, etc.

_Rubber and gutta-percha cements._ Caoutchouc, commonly called India
rubber, or briefly rubber, is derived from the milky juices of
certain tropical plants. It is distinguished by great elasticity and
indifference to chemical agents.

Both these properties make it a valuable material for cement, and it
is much used for this purpose either in the form of solution or as
a constituent of other compositions. For cements which are to have
a certain degree of elasticity combined with indifference toward
chemical agents, it is absolutely indispensable, as no other known body
possesses these properties in such a high degree.

The derivation of gutta percha is similar to that of rubber. At an
ordinary temperature it forms solid and very tenacious masses, of a
leather-like consistency, but at a somewhat higher temperature (below
the boiling-point of water) it is converted into a very plastic, soft
mass, which can be drawn into very fine threads, and rolled to very
thin plates.

By itself or mixed with other substances it furnishes an excellent
cement, possessing the valuable properties of tenacity and pliancy
when exposed to shocks. As regards resistance to the action of water
and chemical agents it is almost equal to rubber, and, for certain
purposes, is frequently preferred to the latter.

_Glue and starch cements._ By itself, _i. e._, converted by boiling
with water into a viscous mass which solidifies on cooling, glue cannot
be classed with the cements; the same applies to paste, _i. e._, starch
or flour swelled and boiled in water.

But compounded with other substances both yield excellent cements,
in which a part of the properties distinguishing glue solution and
paste is preserved. They both possess the property of decreasing the
brittleness of many cements, but unfortunately the latter thereby lose
their power of resisting the action of water; for starch as well as
glue swells in water, and the latter, when moist, passes quickly into
putrefaction and destroys the cement.

In a wider sense isinglass, compounds of glue and vinegar, of lime and
glue, etc., must be classed with the glue cements, and ordinary flour
and shoemakers’ paste with starch cements.

_Lime Cements._ Lime possesses the property of forming insoluble
combinations with egg albumen or caseine, this being the reason why
lime cements, of which there are a great number, are generally composed
of burned lime and one or the other of the above substances. Lime
compounded with a solution of water-glass forms also very solid and
durable cements.

Although the cements and agglutinants mentioned in the foregoing
are most frequently used, a compound of different cements is often
employed, in consequence of which the composition of many cements is
very complicated.

In the following we give a description of the preparation of the
different kinds of cement, according to the manner of their employment.

CHAPTER XIII.

PREPARATION OF CEMENTS, PASTES, AND MUCILAGES.

OIL CEMENTS.

Oil cements, as already explained, must be considered as a variety
of soaps insoluble in water, formed by the action of drying oils or
varnish upon various basic combinations.

The most important of this class is the cement used for securing
window-panes. Good glaziers’ putty is a product of extraordinary
durability, and, besides for puttying glass and wood, can also be used
for joining many other bodies.

_Putty._ This is prepared by mixing fine whiting with linseed oil or
linseed-oil varnish. The whiting should be passed through a sieve of 42
meshes to the inch. It should be perfectly dry before sifting, and be
thoroughly incorporated with the oil.

As the work of kneading large masses with the hands or feet must be
continued for a long time in order to obtain an entirely uniform
product, and is consequently very laborious, it is recommended to use
the following contrivance:

Two wooden rollers rest in a suitable frame, and can be brought
together or removed from each other by means of two screws. When the
mixture of whiting and linseed oil is of sufficient consistency to
allow kneading, it is fashioned into a cylinder and rolled out between
the above rollers to a long, thin band, which is caught in a vessel.
The band is balled together, the ball reformed into a cylinder, and the
latter again passed through the rollers, the operation of balling and
rolling being continued until a uniform mass is obtained.

The finished product should be kept in oiled paper or under water.
White lead is sometimes mixed with the putty, and other pigments to
give color as desired. Hard putty may be softened by rolling between
the hands.

_French putty._ Boil 7 lbs. of linseed oil with 4 lbs. of burnt umber
for 2 hours. Then add 10 lbs. of white lead and 5½ lbs. of chalk.

_Soft putty._ Whiting 20 lbs., white lead 2 lbs., linseed oil and olive
oil 1 gill each.

Mix the whiting and the white lead with the necessary quantity of
linseed oil, to render the putty of the proper consistence, the olive
oil being added to the linseed oil before kneading. The object of using
olive oil is to prevent the white lead from hardening, and it preserves
the putty in a state sufficiently soft to adhere at all times, and not,
by getting hard and cracking off, suffering the wet to enter, as is
often the case with ordinary hard putty.

_Litharge cement._ By mixing litharge reduced to a fine powder with
linseed oil, a yellow cement is obtained which gradually solidifies to
a mass as hard as stone.

_Red lead cement_ is made by mixing red lead with linseed oil to a
paste. It is used for cementing the joints of metal pipes.

Lead preparations furnish excellent cements, but have the disadvantage
of great weight and a high price. For many purposes a part of the lead
combination can be suitably replaced by a substance of less weight,
such as whiting, or, still better, burned lime slacked with sufficient
water to convert it into a powder.

The quantity of the substitute added varies very much, there being,
for instance, many varieties of so-called red lead oil cement, which
contain only about 10 per cent. of red lead.

_Cement for wash basins._ Finely powdered glass (sifted) 2 parts,
litharge 2 parts, linseed-oil varnish 1 part.

Wet the powders slightly with the oil, heat and gradually add the
rest. Do not use the basin for several days. Finely powdered glass or
glass meal may be made by heating glass, throwing it in cold water,
grinding the fractured pieces, and washing by stirring up in water, and
allowing the finer particles to float off into a second vessel. Collect
this fine powder when sufficient has settled in the vessel and sift it
through a very fine sieve.

_Zinc-white cement_ is prepared similar to putty or red-lead cement.
It may, however, be made as follows: Mastic 2 parts, dammar 4 parts,
sandarac 6 parts, Venetian turpentine 8 parts, turpentine 10 parts,
benzole 12 parts, zinc white 14 parts.

The resins are powdered, while the Venetian turpentine, ordinary
turpentine, and benzole, are put in a bottle, and then the powdered
resins put in. The whole is shaken and allowed to stand for the resins
to dissolve. The solution is filtered through cotton-wool and rubbed
up with sufficient zinc-white to form a cement. Dilute with benzine if
necessary.

_Mastic cement, mastic or pierres de mastic._ Under this name masses
are brought into commerce which are well adapted for moulding
ornaments, such as figures, columns, etc., to be exposed to the
weather. They are comparatively cheap, and it is rather remarkable that
they are not more generally known and used for technical purposes.

To prepare large quantities of this cement suitable mills and mixing
vessels are required, as the conversion of the materials into a
dust-like flour is an indispensable condition of the success of the
work. The materials most generally used are fine quartz sand, finely
ground calcareous sand, and varying quantities of litharge or zinc
oxides, besides as small a quantity of linseed oil as possible.

The linseed oil combines with the litharge or zinc oxide to an
insoluble soap, which incloses the other material and forms a mass
acquiring the hardness of sandstone in thirty to fifty hours.

After converting the materials into a fine powder, the mixing is
accomplished in barrels filled about three-quarters full and revolved
by water-power. When a thorough mixture has been effected the
pulverulent mass is placed in sheet-iron vessels and saturated with
linseed oil, and then moulded at once, as it solidifies in one or two
days.

_French mastic._ Quartz sand 300 parts, pulverized limestone 100,
litharge 50, linseed oil 35.

_Paget’s mastic._ Sand 315 parts, whiting 105, white lead 25, calcined
red lead 10, lead acetate solution 45, linseed oil 35.

The mastic may be colored by adding pigments.

_Water-proof cement._ _A._ Rubber 7 parts, oil of turpentine 140,
linseed oil 40. _B._ Turpentine 100 parts, sulphuric acid 3, zinc-white
10.

To prepare solution _A_, place the rubber in the oil of turpentine in a
bottle. It swells very much without actually dissolving. After adding
the linseed oil, reduce the entire mass by boiling to one-half the
volume originally occupied by it.

Solution _B_ is prepared by stirring the sulphuric acid into the
turpentine and allowing it to stand for twelve hours. To remove the
sulphuric acid, the thick mass which has been formed is then kneaded in
water in which the zinc oxide has been distributed. After drying, the
resulting mass is dissolved in the warm fluid _A_.

_Another formula_ is as follows: Linseed oil 8 parts, litharge 12,
burnt lime 88.

Boil the linseed oil and litharge half an hour, then stir the lime into
the hot mass, and use the mixture hot. This cement is excellent for
filling in joints between stones, for flat roofs, water reservoirs,
etc. For a better adhesion of the cement, apply a coat of linseed
oil varnish to the surfaces to be cemented. Porous stones are made
water-proof by heating the cement in a boiler and adding sufficient
linseed oil to form a mass which can be readily worked with a smoothing
board. Apply as hot as possible.

_Serbat’s mastic._ Pyrolusite 60 parts, sulphate of lead 60, linseed
oil 10.

After thoroughly drying the materials, mix the sulphate of lead with
the linseed oil, then add 20 parts of the pyrolusite and, after mixing
and working it thoroughly, add gradually the rest of the pyrolusite in
small portions and kneading constantly.

_Stephenson’s oil cement._ Litharge 20 parts, unslaked lime 10 parts,
sand 10 parts, hot linseed oil 3 parts.

_Alum cement._ Dissolve good hard soap, by heating in rain water,
dilute the thickly fluid mass and add saturated alum solution as
long as a precipitate is formed. Collect the gelatinous precipitate
of alumina soap thus formed upon a cloth, and, after draining, pour
rain water over it ten to twelve times to remove the salts as much as
possible. After washing, dry the alumina soap, and rub it to a fine
powder.

To prepare cement rub a portion of the powder with sufficient
linseed-oil varnish to form a plastic dough, which is used for filling
in the joints.

This cement is water-proof, resists high temperatures without being
absolutely fire-proof, and, on account of its light color, is well
adapted for joining marble plates, etc.

_Oil cement for glass._ Litharge 30 parts, burnt lime 20, pipe-clay 10,
linseed-oil varnish 6.

_Oil cement free from lead for steam pipes._ Graphite 12 parts, heavy
spar 16, slaked lime 6, boiled linseed oil 6.

_Oil cements for steam pipes._ I. Litharge 25 parts, air-slaked lime
10, quartz sand 10.

Mix the ingredients quickly with the linseed oil and work the mass
thoroughly in a hot mortar. Coat the defective places in the pipes with
linseed-oil varnish, apply the cement hot and when partially solid,
make it still tighter by heating.

II. Boil 60 parts of graphite, 50 of air-slaked lime, 60 of elutriated
heavy spar in 35 of linseed oil, stirring constantly. Apply the mixture
hot.

_Oil cement for marble._ Elutriated litharge 10 parts, brick dust 100,
linseed oil 20.

Prepare in the same manner as glaziers’ putty. For various colors add
zinc white for white, red lead for red, pyrolusite for brown, etc.
Previous to applying the cement saturate the surfaces of the stones to
be cemented with linseed-oil varnish.

_Oil cement for porcelain._ Stir 20 parts of white lead and 12 of white
pipe-clay into 10 of boiling linseed oil previously boiled and knead
the mass thoroughly. After cementing let the articles stand quietly for
several weeks.

_Diamond cement._ Litharge 30 parts, air-slaked lime 10, whiting 20,
graphite 100, linseed oil 40. Apply hot. This is an excellent cement
for metal.

_Hager’s diamond cement._ Whiting 16 parts, elutriated graphite 50,
litharge 16.

Mix the pulverized ingredients with sufficient old, thick linseed oil
to form a plastic dough.

RESINOUS CEMENTS.

_Resinous cement for amber_ is obtained by melting mastic in linseed
oil. Volatile copal lacquer can also be advantageously used for the
purpose.

_Cement for turners._ Melt 1 lb. of rosin in a tin can over the fire,
and when melted add 4 ozs. of pitch; while these are boiling add brick
dust until, by dropping a little on a cold stone, you think it is hard
enough. In winter it may be found necessary to add a little tallow.

By means of this cement a piece of wood may be fastened to the chuck,
which will hold when cool, and when the work is finished, it may be
removed by a smart blow with the tool. All traces of the cement may be
removed from the work by repeated applications of benzine. To use this
cement, chip off as much as will cover the chuck to the 1/16th of an
inch, spread it over the surface in small pieces, mixing it with ⅛ of
its bulk of gutta-percha, then heat an iron to a dull red heat, and
hold it over the chuck till the mixture and gutta-percha are melted and
liquid. Stir the cement until it is homogeneous, chuck the work, lay
on a weight to enforce contact, leave it at rest 20 minutes.

The following cement is much employed and serviceable for the use of
turners and artisans in general.

Reduce 1 lb. of whiting to a fine powder, and heat to redness so as to
expel all the water. When cold this is mixed with 1 lb. of black rosin
and 1 oz. of beeswax previously melted together, and the whole stirred
till of uniform consistence.

_Cement for ivory and bone._ Melt at a moderate heat equal parts of
white wax, rosin, and oil of turpentine to form a thickly-fluid mass.
For coloring the cement add elutriated red lead, ultramarine, etc.

_Cement for white enameled clock-faces._ Dammar resin 100 parts, copal
100, Venice turpentine 110, zinc white 60, ultramarine 3.

Apply hot and polish when cold and hard.

_Cements for glass._ 1. Melt carefully 60 parts of bleached shellac and
10 of turpentine. If too thick, dilute with turpentine.

2. Shellac 20 parts, elemi 5, turpentine 10. Prepare as above.

_Cement for glass upon glass._ Shellac 10 parts, turpentine 2,
pulverized pumice stone 10.

_Cement for glass upon metal._ Melt together 40 parts of rosin, 20 of
rouge, 10 of wax, and 10 of turpentine. Apply hot to the surfaces to be
cemented.

_Cement for metal letters upon glass._ Rosin 42 parts, turpentine 4,
plaster of Paris 5.

_Cement for wood._ 100 parts of shellac and 45 of strong spirit of wine.

This cement serves for joining wood, which, on account of exposure to
water, cannot be glued. Apply the cement to the surface of one of the
pieces, and after placing upon it a piece of tissue paper press upon it
the other piece of wood previously coated with the cement.

_Cement for knife handles._ Melt together 20 parts of rosin, 5 of
sulphur, and 8 of iron filings.

Pour some of the hot mixture into the handle, and then push in the
knife previously heated.

_Cement for petroleum lamps._ Boil 12 parts of rosin in 16 of strong
lye until it is entirely dissolved and on cooling forms a tenacious
solid mass. Dilute this with 20 parts of water, and carefully work into
it 20 parts of plaster of Paris. This cement is insoluble in petroleum,
and is especially adapted for cementing the glass parts of lamps to the
metal. It is also a good material for stoppers for petroleum bottles.

_Cement for porcelain._ Rosin, 14 parts; elemi, 7; shellac, 7; mastic,
7; sulphur, 42; brick dust, 20.

_Cement for porcelain which is to be heated._ Heat carefully 10 parts
of amber in a large spoon, stirring constantly, until it evolves heavy
vapors of a strong odor. Rub the melted mass as finely as possible,
and after placing the powder in a bottle pour over it a mixture of
bisulphide of carbon and benzine. Close the bottle air-tight to
prevent the evaporation of the very volatile solvent. When the powder
is dissolved remove the cork and replace it by one provided with a
small brush. The application of the cement and pressing together of
the parts to be cemented must be effected as quickly as possible.
In articles properly cemented the joint can only be detected by the
closest examination. This cement holds so well that cups and saucers,
soup-tureens, etc., mended with it can be used for years.

_Cement to withstand the action of petroleum._ Dissolve 5 parts of
shellac, 1 of turpentine in 15 of petroleum. This cement is quite
elastic.

_Cement for mica._ A colored cement for joining sheets of mica is
prepared as follows: Soak clean gelatine in water, and when swelled
squeeze out the excess of water by pressure between a cloth, then melt
the gelatine by the heat of a water-bath, and stir in just enough proof
spirit to make it fluid. To each part of this solution add, while
stirring, ¼ oz. of gum ammoniac and 1½ ozs. of gum mastic dissolved in
4 ozs. of rectified alcohol. Put the mixture into bottles, and when
required for use stand the bottle in hot water. This cement resists
cold water.

_Cement for horn, whalebone and tortoise shell._ Dissolve gum mastic 10
parts and turpentine 4, in 12 of linseed oil. Apply hot.

_Cement for terra-cotta articles._ Melt together 70 parts of rosin,
70 of wax and 16 of sulphur, and stir into the mass 8 parts of hammer
slag and 8 of quartz sand. Coat the fractured surfaces with oil of
turpentine, apply the cement as quickly as possible, and press the
surfaces together. It is advisable to heat the terra cotta previously
to 158° or 176° F. After cementing the article, smooth the joint with a
heated knife and dust very fine terra-cotta powder through a linen bag
upon the soft cement in order to give it exactly the same color as the
article itself.

_Mastic cement for glass._ Gum mastic 15 parts, bleached shellac 10,
turpentine 5.

This mass sufficiently diluted with hot oil of turpentine furnishes
an excellent cement for fractured glass and gems. Being colorless,
the joint can scarcely be detected, provided the cementing has been
skilfully done.

To attach gems to glass of the same color, the cement is colored with
aniline colors dissolved in spirit of wine, care being had to give it
the same shade as the gem and the glass.

_Stick mastic cement._ Melt together, at as low a temperature as
possible, 10 parts of mastic and one of turpentine, and pour the mass
into suitable moulds.

For use, heat the fractured surfaces of the article strongly, so that
the cement on being rubbed over them melts, then press the surfaces
together and continue the pressure until the cement solidifies.

_Sulphur cement for porcelain._ White pitch 18 parts, sulphur 28,
bleached shellac 4, gum mastic 8, elemi 8, glass meal 28. Melt all
together, except the glass meal and stir the latter into the melted
mass.

_Insoluble cement for wooden vessels._ Melt together 60 parts of rosin,
20 of asphalt, and 40 of brick dust. Pour the hot mixture into the
joints. This cement resists the action of lye, quick lime, sulphuric
and hydrochloric acids.

RUBBER CEMENTS.

These cements are very useful, but owing to the inflammable nature of
the components, great care should be taken to guard against fire while
preparing them. They should never be made near a naked fire, as the
benzine, carbon disulphide or chloroform used to dissolve the rubber is
very volatile, and the vapor given off permeates the air until, coming
near a source of light, the whole air becomes one vivid sheet of flame.
Vessels which are used should be closed, and if possible put out of
doors. If heat is required to assist the solvent action, use a sand or
hot-water bath, but on no account bring near a fire.

_Cements for glass._ I. Rubber 1 part, gum mastic 12, dammar 4,
chloroform 50, benzine 10.

II. Rubber 12 parts, chloroform 500, gum mastic 120.

This cement adheres immediately, and possesses a high degree of
elasticity. It may be used to advantage for joining together the glass
panes of hot-houses.

III. Dissolve, without application of heat, rubber 2 parts and gum
mastic 6, in 100 of chloroform. This cement is perfectly transparent.
It should be applied as quickly as possible, as it sets in a very short
time.

_Soft rubber cement._ Melt 10 parts of tallow in a brass pan and
gradually add 150 parts of rubber in small pieces, and stir constantly
until all the rubber is dissolved. Keep in readiness a well-fitting
lid to be able to extinguish the flame immediately in case the rubber
catches fire. When all is melted stir in 10 parts of slaked lime.

This cement is especially adapted for sealing bottles containing
caustic substances, such as nitric acid, etc. It remains always
tenacious, being therefore suitable for cementing bodies exposed to
repeated shocks.

_Hard rubber cement._ Rubber, 150 parts; tallow, 10; red lead, 10.

This cement is prepared in the same manner as the above. The addition
of red lead gives it a red color, and solidifies it in a short time to
a mass as hard as stone.

_Elastic cement._ Carbon disulphide, 8 ozs.; fine rubber, 1 oz.;
isinglass, 4 drachms; gutta-percha, 1 oz. Dissolve the solids in the
fluid.

This cement is used for cementing leather and rubber. For use the
leather is roughened and a thin coat of the cement applied and allowed
to dry completely; then the two surfaces to be joined are warmed and
placed together and allowed to dry.

_Marine glue._ This cement, which is only a glue in name, is
water-proof, and can be used to cement metal, wood, glass, stone,
pasteboard, etc., and is especially adapted for caulking vessels.

Suspend 10 parts of rubber inclosed in a bag in a vessel containing 120
parts of refined petroleum, so that only half of the bag is immersed,
and allow it to remain ten to fourteen days in a warm place. Then melt
20 parts of asphalt in an iron boiler and add the rubber solution in a
thin jet, and heat the mixture, while constantly stirring, until it is
perfectly homogeneous. Pour it into greased metallic moulds, where it
forms into dark-brown or black plates difficult to break. In using it,
it should be melted in a kettle placed in boiling water to prevent its
burning, which it is very apt to do, as it is a bad conductor of heat.
After it has been liquefied remove the kettle from the water and place
it over a fire, where it can be heated, if necessary, to make it more
fluid, to 302° F., carefully stirring it to prevent burning.

If possible, the surfaces to be glued together should be heated to
212° F., as the glue can then be slowly applied. The thinner the layer
of glue in cementing together smooth surfaces, the better will it
adhere. But a somewhat thicker layer is required for rough surfaces,
for instance, boards not planed, the excess of glue being forced out by
strong pressure. Generally speaking, it is best to subject all articles
cemented together with marine glue to as strong a pressure as possible
until the glue is congealed.

Repeated experiments have shown that with the aid of this cement square
vats perfectly water-tight can be constructed of boards. Wooden pegs
dipped in the compound should be used for putting the vats together.

_Jeffrey’s marine glue._ Dissolve 1 part of rubber in benzine, and mix
the solution with 2 parts of shellac by the assistance of heat.

_Another formula_ is as follows: Coal naphtha 1 quart, rubber cut in
shreds 2 ozs. Macerate for 10 or 12 days and then rub smooth with a
spatula on a slab; add 2 parts by weight of shellac to 1 part of this
solution. To use the compound melt it at about 240° F.

_Marine glue for damp walls._ Rubber 10 parts, whiting 10, oil of
turpentine 20, carbon disulphide 10, rosin 5 and asphalt 5. Dissolve
the ingredients in a suitable vessel and stand in a warm place, shaking
it frequently.

Scrape the wall smooth and clean, and apply the glue with a broad brush
on the damp place and about 8 inches higher than the line of dampness.
Before the glue is dry lay on plain paper which will adhere tightly. On
this plain paper the wall paper can be pasted in the usual manner. If
carefully done, the wall paper will always remain dry.

GUTTA-PERCHA CEMENTS.

_Cement for leather._ Gutta-percha 100 parts, pitch or asphalt 100, oil
of turpentine 15.

This cement should be used hot. It is suitable for cementing all kinds
of substances, but adheres particularly well to leather.

_Cement for hard rubber combs._ _A._ Prepare a very thick solution of
bleached gutta-percha in bisulphide of carbon.

_B._ Dissolve sulphur in bisulphide of carbon.

The cementing is effected by applying solution _A_ to the fractured
surfaces and pressing them together. When dry brush solution _B_ over
the cemented place.

_Elastic gutta-percha cement._ Dissolve 10 parts of gutta-percha in 100
of benzine, then pour the clear solution into a bottle containing 100
parts of linseed-oil varnish and unite both by shaking. This cement
excels in elasticity, and is especially suitable for attaching the
soles of shoes, as it is so elastic that it will not break, no matter
how much it is bent. To make it adhere tightly roughen the leather on
the side to be cemented.

_Cement for horses’ hoofs._ For filling cracks and fissures in horses’
hoofs a cement is required which possesses great resistance to the
action of water combined with elasticity and solidity. A mass answering
all demands consists of 10 parts by weight of gum ammoniac and 20 to
25 of purified gutta-percha. Heat the gutta-percha to between 194°
and 212° F., and then work it with the finely powdered gum ammoniac
to a homogeneous mass. In using it, soften the cement by heating, and
after carefully cleansing the crack in the hoof, apply it with a heated
knife. The cement solidifies immediately after cooling to the ordinary
temperature, and becomes soon so hard as to allow of nails being driven
into it.

_Cement for crockery._ Gutta-percha 1 part, shellac 1.

Place the two ingredients in an earthenware jar, and melt the two
together by standing this jar on a vessel of boiling water, or else one
filled with hot sand, the vessel holding the water or sand being heated
over a fire or gas furnace. Stir the melted ingredients well together.
The resulting cement is one possessing great hardness and toughness,
which suits it admirably for mending crockery. Warm the edges to be
joined together, smear the cement on, join together, and hold the
article thus joined until cool.

_Cement for leather._ Mix 10 parts of carbon disulphide with 1 part
of turpentine, and then add sufficient gutta percha to make a tough,
thickly-fluid mass. Before using this cement, free the surface to be
joined from grease. To effect this, sprinkle a little bicarbonate of
soda, carbonate of ammonia or borax on the surfaces to be joined, lay
a cloth over them, and then place a hot iron on top, and keep it there
a short time so as to cause the alkali to cut the grease, then put the
cement on both surfaces to be joined, put them together and subject to
pressure until they are cemented.

Gutta percha dissolved in carbon disulphide to the consistency of syrup
is also a good cement for joining leather. The parts to be joined
should be well covered with cement so as to fill the pores of the
leather, then the cement is heated and the parts hammered until the
cement is cold.

CASEINE CEMENTS.

_Preparation of pure caseine._ Although the caseine contained in old
cheese can be used, the other constituents, such as fat, salt, and free
acid, exert an injurious influence upon the solidity of the cement
prepared with it. It is, therefore, best to prepare pure caseine, which
is easily accomplished in the following manner:

Put milk in a cool place, and after taking off the cream as long as any
is formed, remove the skimmed milk to a warm place to coagulate. After
heating the curd, place it upon a filter and wash the caseine remaining
upon the filter with rainwater until the water running off shows no
trace of acid.

To remove the last traces of fat tie the washed caseine in a cloth and
after boiling it in water, spread it upon blotting paper in a warm
place to dry. It will shrivel up to a horny mass.

When thoroughly dried pure caseine will keep for a long time without
suffering alteration. To obtain the caseine in a form suitable
for preparing cements it is only necessary to pour water over a
corresponding quantity and allow it to stand for some time. Caseine
combines with lime to a hard insoluble mass.

Ordinary technical caseine may be readily and cheaply prepared as
follows: Skim milk is heated in a copper boiler, if necessary by the
introduction of steam, to 122° F. Then add for every 1000 quarts of
milk, 3 quarts of crude hydrochloric acid diluted with 5 to 6 times
the quantity of water. After coagulation, the whey is drained off, the
curd spread out upon an inclined table and allowed to cool. The curd is
then washed by pouring cold water over it through a rose, or stirring
it up with water in a barrel, allowing to settle, and pouring off the
supernatant water. The residue is subjected to moderate pressure. The
caseine while still moist is comminuted in a curd-mill and packed in
bags. In this state it must be worked at once, as otherwise it spoils
readily and is attacked by worms. If it is to be kept for a longer
time, it has to be dried. This is effected by spreading it out upon
linen cloths and placing it in a drying chamber.

In this manner 8.5 per cent. of moist, or 3.5 per cent. of dry, caseine
is obtained which is brought into commerce as technical caseine or
lactarine. It being insoluble in water, 10 per cent. of an alkali—soda,
borax, or ammonia—has to be added to effect solution. Water-soluble
caseine is seldom found in commerce, the consumer preparing it, as a
rule, himself.

A purer technical caseine is obtained according to John A. Just’s
method as follows: Dissolve, stirring constantly, in 115 quarts of
water heated to between 104° and 131° F., 17 to 26 ozs. of bicarbonate
of soda and 176 lbs. of moist, or 118 lbs. of dry, caseine, and dry the
solution upon a heated revolving metal cylinder. After each revolution
of the cylinder, the dry material is scraped off with brushes and by
being forced through a fine-meshed sieve yields soluble caseine powder.

_Caseine cement which can be kept for a long time._ Convert into
powder, each by itself, 200 parts of caseine, 40 of burned lime, and
1 of camphor. Mix the powders intimately and keep the mixture in an
air-tight bottle. For use, mix some of the powder with the requisite
quantity of water and use the cement at once.

_Cement for glass._ Old dry cheese 100 parts, water 50, slaked lime 20.

Free the cheese from rind, and rub it with the water until a
homogeneous mass drawing threads is formed. Then stir in quickly the
lime powder, and use the cement at once. It unites not only glass to
glass, but can also be used for cementing metal to glass.

_Cement for metals._ Elutriated quartz sand, 10 parts; caseine, 8;
slaked lime, 10, and sufficient water to form a cream-like mass.

_Cement for porcelain._ Caseine dissolves readily in solution of
water-glass, and forms then one of the best cements for porcelain
known. To prepare it, fill a bottle one-quarter full with fresh
caseine, and after filling the bottle with solution of water-glass,
effect the solution of the caseine by frequent shaking.

_Cement for meerschaum._ Dissolve caseine in water-glass, and after
stirring quickly finely-pulverized calcined magnesia into the mass, use
it at once, as it solidifies very soon. By adding, besides magnesia,
genuine meerschaum finely pulverized, a mass closely resembling
meerschaum is obtained, which can be used for manufacturing imitation
meerschaum.

_Cement for wood, etc._ Rub 10 parts of caseine and 5 of borax
to a thick, milky mass, and use it like glue. This cement can be
advantageously used for pasting labels upon wine bottles, as it neither
moulds nor becomes detached in the cellar.

_Another formula_ is as follows: Dissolve borax by boiling in water,
and pour the solution over fresh caseine. The result will be a clear,
thick mass of extraordinary power of adhesion, which can be kept for
any length of time without suffering decomposition.

Applied to leather, paper, linen or cotton goods, it forms a coat of
beautiful lustre, and for this reason is much used in the manufacture
of fancy articles of paper and leather.

_Cement for porcelain._ Dissolve 10 parts of caseine in 60 of
water-glass solution. Apply the cement quickly and dry the cemented
articles in the air.

WATER-GLASS AND WATER-GLASS CEMENTS.

_Water-glass._ Water-glass (silicate of soda or soluble glass) is
found in commerce as a thickly-fluid, tenacious mass. It is generally
prepared by fusing 15 parts of quartz sand with 8 of carbonate of
soda and 1 of charcoal. The silicic acid combining with the soda
disengages the carbonic acid, the expulsion of which is facilitated by
the presence of charcoal, which converts it into carbonic oxide. It
dissolves readily in water. The solution has a strongly alkaline taste,
and possesses the property of being gradually converted, on exposure to
the air, to a gelatinous mass which finally solidifies. For this reason
water-glass should be kept in bottles hermetically closed with corks.
Glass stoppers are of no use, as they are so firmly cemented to the
bottle that on attempting to open the latter the neck breaks off.

By combining water-glass with cement or burned lime the resulting mass
solidifies quite rapidly to a mass as hard as stone, and generally
capable of resisting chemical action.

Water-glass by itself is only fit for cementing glass to glass, but
combined with other substances it furnishes very durable and solid
cements.

_Cement for cracked bottles._ Select a cork which will fit the bottle
air-tight and place it loosely upon the bottle, and heat the latter
gradually to at least 212° F. Then press the cork down and apply a
thick solution of water-glass to the cracks. In cooling, the air in the
bottle contracts strongly, and the pressure of the exterior air drives
the water-glass with great force into the cracks closing them entirely
so that they cannot be detected.

_Cement for glass and porcelain._ Stir quickly together 10 parts of
elutriated glass meal, 20 of powdered fluor spar, and 60 of water-glass
solution, and apply the homogeneous paste at once. In a few days the
cement will be so hard that the cemented vessels can be heated without
danger.

_Cement for hydraulic works._ Finely powdered cement, and solution of
water-glass. Mix the two bodies quickly together.

As this cement hardens very quickly, it should be used fresh. It
hardens under water, and is therefore excellent for hydraulic works.
The stones should be coated with a solution of water-glass before
applying the cement.

_Cement for uniting metals._ A strong cement, which hardens rapidly, is
made by stirring the finest whiting in a solution of soda-glass of 33°
B., made so as to form a plastic mass. This can be readily colored to
any desired shade. The addition of sifted sulphide of antimony gives
a black cement, which by polishing acquires a metallic lustre; iron
filings render it grayish-black; zinc dust turns it green, but after
polishing, it appears like metallic zinc, and may be employed for the
permanent repair of zinc ornaments, etc. Carbonate of copper imparts a
light green shade. Other additions may be made, as oxide of chrome for
dark green, cobalt blue for blue, red lead for orange, vermilion for
scarlet, carmine for violet, etc.

_Cement for tightening joints of pipes exposed to a red heat._ Mix 80
parts of pyrolusite, 100 of zinc white, and 20 of water-glass.

This cement fuses at a temperature not too high, and then forms a
glass-like mass which adheres very firmly and closely.

_Cement for marble and alabaster._ The point of fracture of articles
cemented with the following mixture is difficult to find, and the
cemented place is much stronger than the material itself. Mix 12
parts of Portland cement, 6 of slaked lime, 6 of fine sand, and 1 of
infusorial earth with sufficient water-glass to form a thick paste. The
article to be cemented need not be heated. It hardens in twenty-four
hours.

GLYCERINE AND GLYCERINE CEMENTS.

Commercial glycerine is a yellowish or nearly colorless and more or
less viscid liquid having an intensely sweet taste. In combination with
lead oxide and intimately worked into it, by heating and stamping,
it furnishes very strong and durable cements deserving general
introduction, though thus far they have been but little used.

For the manufacture of cements the use of pure odorless glycerine
is not required, the yellow crude article, which is much cheaper,
answering all purposes. The principal point is to use very highly
concentrated glycerine, as otherwise the cements prepared with it
solidify very slowly and besides do not possess a proper degree of
hardness and solidity.

It is of especial importance to have the lead oxide free from water. To
accomplish this, heat it thoroughly and mix it with the glycerine while
still hot. Cement thus prepared solidifies very quickly, and can be
used for many purposes. It is an excellent material for quickly joining
the stones of submarine works.

_Glycerine and litharge cement._ Moisten elutriated litharge with
glycerine so that a thin homogeneous paste is formed. This cement is
adapted for uniting the joints of steam pipes, cementing wood, glass,
porcelain, and also glass upon metal, etc. It solidifies to a very hard
mass in a quarter to three-quarters of an hour. Before applying the
cement coat the surfaces to be joined with pure glycerine.

LIME CEMENTS.

Quick lime, slaked lime and chalk are used for this purpose. Quick
lime, which is obtained by burning limestone, combines gradually with
the fats to insoluble lime soaps. Slaked lime, which consists of a
combination of lime with water, acts in the same manner.

For the preparation of cements the lime is slaked by placing it in a
dish and pouring as much water over it as it will absorb. Good lime,
technically called _fat lime_, should eagerly combine with water,
evolving much heat, swelling greatly, and crumbling to a light white
powder.

Quick lime exposed to the air until, by the absorption of moisture and
carbonic acid, it is converted into a powder is called _air-slaked_.

Cements prepared with quick lime will, as a rule, solidify more quickly
than those prepared with air-slaked lime.

Chalk is a carbonate of lime consisting of the shells of microscopic
animals, and can be readily pulverized and elutriated. In the latter
state it is known as _whiting_. For the preparation of entirely white
cements the use of pure white lime or chalk is absolutely necessary.
Yellow or reddish lime contains oxide of iron, and furnishes cements of
the same tinge.

_Cement for glass._ Litharge 30 parts, quick lime 20, linseed-oil
varnish 5.

_Cement for joiners._ A cement for filling up cracks and holes is
obtained by mixing slaked lime 50 parts, flour 100, linseed-oil varnish
15.

_Cement for cracked clay crucibles and porcelain._ By applying to the
cracks a mixture of 10 parts of slaked lime, 10 of borax, and 5 of
litharge in sufficient water to form a stiff paste, and drying after
heating the crucible, the cracked places will be united so firmly that
the crucible, when thrown to the ground, will generally break in any
other place than the cemented one.

This cement can also be used for porcelain capable of standing a strong
heat.

_Lime and glue cement._ Stir air-slaked lime into hot glue. This cement
is especially suitable for attaching metal to glass. It forms a very
hard yellowish-brown mass.

GYPSUM CEMENTS.

Sulphate of lime in combination with water is met with in nature, both
in the form of transparent prisms of _selenite_, and in opaque and
semi-opaque masses, known as _alabaster_ and _gypsum_. By pulverizing
the latter and heating to about 302° F. it loses its water, and is
converted into anhydrous gypsum or _plaster of Paris_, which on mixing
with water recombines with it to form a mass of hydrated sulphate of
lime, the hardness of which nearly equals that of the original gypsum.
When the powder is mixed with water to a cream and poured into a mould,
the minute particles of anhydrous sulphate of lime combine with the
water to reproduce the original gypsum, and this act of combination
is attended with a slight expansion which forces the plaster into the
finest lines of the mould.

By using a solution of alum instead of ordinary water, a plaster is
obtained which, although it takes much longer to set than the ordinary
kind, is much harder, and therefore takes a good polish.

For preparing cements only perfectly white plaster of Paris should be
used, as the gray article possesses but little adhesive power.

_Cement for plaster of Paris statues._ To repair plaster of Paris
statues so that the point of fracture cannot be detected, proceed in
the following manner:

Moisten the fractured surfaces with water by means of a brush until
they absorb no more and remain moist. Mix plaster of Paris with
water to a thin cream and stir until the heat appearing at first has
ceased, which will prevent the conversion of the plaster into a solid
coherent mass. Apply quickly a thin layer of the plaster to one of the
fractured surfaces, press the other against it until the plaster has
set, and, when dry, carefully remove the excess by scraping.

_Cement for glass and porcelain._ Mix quickly 50 parts of plaster of
Paris, 10 of quick lime, and 20 of white of egg. Use at once, as the
cement solidifies very rapidly.

_Cement for iron and stone._ A very useful cement for securing iron
railing in stone is obtained by mixing 30 parts of plaster of Paris, 10
of iron filings and 20 of vinegar.

_Cements for porcelain._ I. Mix plaster of Paris with saturated
solution of alum to a cream. After moistening the fractured surfaces
apply a thin layer of the cement, press the surfaces together, wrap a
wire or cord tightly around them, and let the article stand quietly for
a few weeks. The cement is converted into a mass as hard as stone.

II. Mix plaster of Paris with a thick, clear solution of gum arabic and
cement the articles as soon as possible. Although this cement adheres
very tightly, porcelain vessels cemented with it cannot be used for
liquids.

_Universal plaster of Paris cement._ Mix 21 parts of plaster of Paris,
3 of iron filings, 10 of water, and 4 of white of egg. This cement is
suitable for attaching metal to glass, metal to stone, etc.

IRON CEMENTS.

_Heat-resisting cement._ Clay 10 parts, iron filings 5, vinegar 2,
water 3.

_Water and steam-proof cement._ Iron filings 100 parts, sal-ammoniac 2,
water 10.

This cement rusts very much in a few days, and is converted into an
extremely solid mass which is perfectly steam- and water-proof.

_Cement for iron._ Mix 65 parts of wrought-iron filings, 2.5 of sal
ammoniac, and 1.5 of flowers of sulphur, and then add 1 part of
sulphuric acid diluted with sufficient water to form a stiff paste.
This cement solidifies in two to three days, and rusts, with the parts
of iron to be cemented, to an extraordinarily durable mass.

_Fire-proof cement for iron pipes._ Wrought-iron filings 45 parts, clay
20, fire-clay 15, common salt solution 8.

_Cements resisting high temperatures._ 1. Iron filings 20 parts, clay
powder 45, borax 5, common salt 5, pyrolusite 10.

Dissolve the borax and common salt in the water, add and mix quickly
the clay powder, pyrolusite, and iron filings. Apply the cement at
once. Exposed to a white heat, it hardens to a tightly adhering, glassy
mass.

2. Mix 52 parts of pyrolusite, 25 of zinc white, and 5 of borax with
solution of water-glass to a paste, and use at once. This cement
requires to be gradually dried. It will stand the highest temperatures.

_Cement for filling in defects in castings._ Stir 100 parts of iron
filings free from rust with sufficient water to form a thick paste, and
press the mixture into the fissures, cracks, etc. The cement becomes
solid only after the iron filings become strongly rusted. To free the
ingredients from adhering fat, wash them, before mixing, in liquid
ammonia.

_Cement for cracked stove plates, etc._ Knead 20 parts of iron filings,
12 of iron scale, 30 of plaster of Paris, and 10 of common salt with
blood to a stiff paste, and use at once. Instead of blood, water-glass
can be used, it having the advantage of being odorless on strong
heating, while blood cement evolves a disagreeable odor.

_Cement for iron water tanks._ Knead iron filings with vinegar to
paste. Allow the mixture to stand until it turns brown, and then force
it into the joints by means of a chisel.

_Cement for cracked iron pots._ Knead 10 parts of iron filings and
60 of clay with linseed oil to a thick paste. Before applying it add
a little linseed oil, and allow it to dry slowly. In a few weeks the
cement will be so hard that the vessels can be used without danger.

_Black cement for stoves._ Iron filings 10 parts, sand 12, bone black
10, slaked lime 12, glue water 5.

_Cements for iron stoves._ 1. Pulverize as finely as possible and mix
intimately 4 to 5 parts of clay, 2 of iron filings free from rust, 1 of
pyrolusite, ½ of common salt, and ½ of borax with water to a paste, and
apply the cement quickly to the places to be cemented and allow it to
dry slowly. This cement will stand a white heat, and resist the action
of boiling water.

2. Mix intimately and as quickly as possible 1 part of pulverized
pyrolusite, and 1 of zinc white with solution of water-glass to a
plastic mass, which solidifies quickly. The power of resistance of this
cement, it is claimed, is not inferior to No. 1, though experiments
have proved No. 1 to be preferable.

CEMENTS FOR CHEMICAL APPARATUS.

Cements to be used for the above purpose must possess various
properties difficult to combine in one preparation. They must be
gas-proof, and capable of resisting the action of different vapors and
acid fluids. As regards resistance to the action of chemical agents,
there is nothing better than caoutchouc, but unfortunately it can
only be used for tightening chemical apparatus not exposed to a high
temperature.

In chemical laboratories bran of almonds, either by itself or kneaded
with water to a thick paste, is frequently used, or rye or wheat
bran mixed with a little flour and water. These cements, though very
suitable for cementing glass distilling apparatus, are strongly acted
upon by chlorine and the vapors of nitric acid.

For small apparatus to be used for the development of fluoric acid,
plaster of Paris mixed with a little water can be used as a cement.
To make the joint entirely gas-tight, paste a strip of paper over it.
Although this cement does not resist the action of fluoric acid for
any length of time, it suffices generally for the protection of the
Workmen during the time the development of the acid is in progress, as,
for instance, in chemical analyses, etc.

To cement chemical apparatus exposed to a temperature not exceeding 86°
to 104° F. paraffine does excellent service; as it possesses the power
of resisting the action of the strongest acids and alkalies.

Below will be found a few receipts for cements which have proved
reliable.

_Linseed oil and clay cement._ Knead 10 parts of dry clay with 1 of
linseed oil to a homogeneous mass. This cement will stand heating to
the boiling-point of mercury.

_Linseed oil, zinc and manganese cement._ Knead 10 parts of pyrolusite,
20 of zinc white, and 40 of clay with sufficient boiled linseed oil
(not exceeding 7 parts) to a plastic mass. This cement will stand a
somewhat higher temperature than the preceding one.

_Cements resisting very high temperatures._ I. Clay 100 parts, powdered
glass 2.

The glass melts on exposure to great heat and slags the clay to a hard
mass. The same effect is produced by adding small quantities of soda
and borax to the clay. An admixture of chalk and boric acid, as in the
following receipt, also gives excellent results.

II. Clay 100 parts, chalk 2, boric acid 3.

_Cement resisting acids._ Melt rubber with double the quantity of
linseed oil, and then knead in sufficient bole to form a paste. This
cement resists the action of nitric and hydrochloric acids, and can
be advantageously used for closing bottles containing them. As it
solidifies very slowly, it can readily be detached from the bottles,
and used again.

For cement which is to solidify quickly on exposure to the air, add a
few per cent. by weight of red lead or litharge.

_Rubber cement for chemical apparatus._ Cut 8 parts of rubber in small
pieces and throw them gradually into a mixture of 2 parts of tallow
and 16 of linseed oil previously strongly heated. After effecting an
intimate mixture of the constituents by vigorous and constant stirring,
add 3 parts of white bole.

Although this cement does not stand a high temperature, it possesses an
extraordinary power of resisting the action of acid vapors.

_Scheibler’s cement for chemical apparatus._ Melt together 1 part of
wax and 3 of shellac, and work into the mixture 2 parts of gutta-percha
cut up in very small pieces. This cement will bear considerable heat
without actually melting.

CEMENTS FOR SPECIAL PURPOSES.

_Cement for attaching metal letters to glass, marble, wood, etc._
Dissolve over a water-bath 5 parts of glue in a mixture of 15 parts
of copal varnish, 5 parts of boiled linseed oil, 3 parts of crude oil
of turpentine, and 2 parts of rectified oil of turpentine, and add 10
parts of slaked lime to the mixture.

_Cement for joints of iron pipes._ Mix 5 lbs. of coarsely powdered iron
borings, 2 ozs. of powdered sal ammoniac, and 1 oz. of sulphur with
sufficient water to form a paste. This composition hardens rapidly, but
if time can be allowed it sets more firmly without the sulphur. It must
be used as soon as mixed, and rammed tightly into the joint.

Another receipt is as follows:

Mix 2 ozs. of sal ammoniac, 1 oz. of sublimated sulphur and 1 lb. of
cast-iron filings or fine turnings in a mortar, and keep the powder
dry. When it is to be used, mix it with 20 times its weight of clean
iron turnings or filings and grind the whole in a mortar; then wet it
with water until it becomes of convenient consistency, when it is to be
applied to the joint. After a time it becomes as hard and strong as the
metal.

_Steam boiler cement._ Mix 10 parts of finely-powdered litharge with
1 part of fine sand and 1 part of air-slaked lime. The mixture may be
kept for any length of time without deterioration. For use a portion
of it is made into a paste with linseed oil or, better, boiled linseed
oil. In this state it must be applied quickly, as it soon becomes hard.

_Cement for rubber._ Powdered shellac is softened in 10 times its
weight of strong water of ammonia, whereby a transparent mass is
obtained, which becomes fluid after keeping some little time without
the use of hot water. In three to four weeks the mixture is perfectly
liquid, and when applied it will be found to soften the rubber. As soon
as the ammonia evaporates it hardens again, and thus becomes impervious
both to gases and to liquids. For cementing sheet rubber, or rubber
material in any shape, to metal, glass, and other smooth surfaces, this
cement is highly recommended.

_Cement for tires._ 1. Isinglass 1 oz., gutta-percha 1 oz., rubber 2
ozs., carbon disulphide 8 fluid ozs. Mix and dissolve.

2. Shellac 4 ozs., gutta-percha 4 ozs., red lead and sulphur, each ½
oz. Melt the shellac and gutta-percha, and add with constant stirring
the red lead and sulphur, melted. Use while hot.

3. Crude rubber 1 oz., carbon disulphide 8 ozs. Macerate 24 hours, and
then add a solution of:

Rosin 2 ozs., beeswax ½ oz., carbon disulphide 8 ozs.

4. Rubber 20 parts, rosin 10, Venetian red 10, tallow 5. Melt the
rubber over a fire, then add the rosin and the tallow and finally the
Venetian red.

_Cement for steam pipes, etc._ A cement of specially valuable
properties for steam pipes, in filling up small leaks, such as a
blow-hole in a casting, without the necessity of removing the injured
piece, is composed of 5 lbs. Paris white and 5 lbs. yellow ochre, 10
lbs. litharge, 5 lbs. red lead and 4 lbs. black oxide of manganese.
Mix the materials thoroughly and make into a paste with a small
quantity of asbestos and boiled linseed oil. The composition, as thus
prepared, will harden in from 2 to 5 hours, and has the advantage of
not being subject to expansion and contraction to such an extent as to
cause a leakage afterwards, and its efficiency in places difficult of
access is of special importance.

_Cement for marble._ Stir to a thick batter with silicate of soda 12
parts of Portland cement, 6 of slaked lime, 6 of fine white lead and 1
of infusorial earth. This is excellent for marble and alabaster. The
cemented objects need to be heated. After 24 hours the fracture is
firm, and the place can scarcely be found.

_Cement for attaching wood, glass, etc., to metal._ Acetate of lead 23
parts by weight, alum 23, gum arabic 38, wheat flour 250.

Dissolve the acetate of lead and the alum in a little water and
separately dissolve the gum arabic in a fair quantity of boiling
water. Thus if the 250 parts of wheat flour represent half a pound,
the quantity of water needed will be about a pint. The gum having
dissolved, add the flour, put the whole on the fire, stir well with a
wooden stick, then add the solution of lead acetate and alum. Continue
the stirring in order to avoid the formation of lumps, then take it off
the fire without allowing it to boil. This cement is used cold, and
will not scale. It is very useful in making wood, glass, cardboard,
etc., adhere to metal, and is extremely strong.

_Brushmakers’ cement._ Rosin 5 lbs., rosin oil or spirit 1 quart.

Reduce the rosin to small pieces, run down in a pot, add the other
ingredient, and stir until mixed and syrupy, then run out into tins.
It is used for cementing the bristles in the stocks, also for string
binding on sash tools, etc.

_Cement for electrical apparatus._ Mix together 1 lb. of beeswax
added to 5 lbs. of rosin, 1 lb. of red ochre, and 2 tablespoonfuls of
plaster of Paris. It will make an excellent composition for electrical
apparatus.

A cheaper composition for cementing voltaic plates into wooden troughs
is made with 6 lbs. of plaster of Paris and ¼ pint of linseed oil. The
ochre and the plaster of Paris should be well dried and added to the
other ingredients when these are in a melted state.

_Jewelers’ cement._ Dissolve over the water-bath 25 parts of fish glue
in a small quantity of strong spirits of wine, add 2 parts of gum
ammoniac; separately dissolve 1 part of mastic in 5 of spirits of wine.
Mix the two solutions and keep them in well-stoppered bottles.

_American cement for jewelers._ Soak 4 ozs. of isinglass in 2 lbs. of
water for 24 hours, then evaporate in the water-bath; to 1 lb. add 1
lb. of rectified spirits of wine, and strain. Then mix in a solution
of 2 ozs. of mastic and 1 oz. of gum ammoniac in 16 ozs. of rectified
spirit.

_Cement for celluloid._ Shellac 2 ozs., spirits of camphor 2, 90 per
cent. alcohol 6 to 8.

_Stratena._ This well-known household cement is said to be prepared
as follows: Dissolve 12 parts of white glue in 16 of acetic acid, and
then add this solution to one of 2 parts gelatine in 16 of water. After
mixing add 2 parts shellac varnish.

_Cement for cloth._ Gutta-percha 16 parts, rubber 4, pitch 2, shellac
1, linseed oil 2 pints. Dissolve the whole by heat, stirring constantly.

HOW TO USE CEMENTS.

It is unquestionably true that quite as much depends upon the manner in
which a cement is applied, as upon the cement itself. The best cement
that was ever compounded would prove entirely worthless improperly
applied. In the foregoing a number of cements have been given which
answer every reasonable demand when properly prepared and properly
used. Good common glue will unite two pieces of wood so firmly that
the fibres will part from each other rather than from the cementing
material; two pieces of glass can be so joined that they will part
anywhere rather than on the line of union; glass can be united to
metal, metal to metal, stone to stone, and all so strongly that the
joint will certainly not be the weakest part of the resulting mass.
What are the rules to be observed in effecting these results?

The first point that demands attention is to bring the cement itself
into intimate contact with the surface to be united. If glue is
employed, the surface should be made so warm that the melted glue
will not be chilled before it has time to effect a thorough adhesion.
The same is more eminently true in regard to cements that are used
in a fused state, such as mixtures of resins, shellac, and similar
materials. These matters will not adhere to any substance unless the
latter has been heated to nearly or quite the fusing point of the
cement used. This fact was quite familiar to those who used sealing-wax
in the olden days of seals. When the seal was used, in succession,
rapidly so as to become heated, the sealing-wax stuck to it with
a firmness that was annoying, so much so that the impression was
generally destroyed, from the simple fact that the sealing-wax would
rather part in its own substance than at the point of adhesion to the
seal. Sealing-wax or ordinary so-called electric cement is a very good
agent for uniting metal to glass or stone, provided the masses to be
united are made so hot as to fuse the cement; but if the cement is
applied to them while they are cold, it will not stick at all. This
fact is well known to those itinerant venders of cement for uniting
earthenware. By heating two pieces of delf so that they will fuse
shellac, they are able to smear them with a little of this gum and
join them so that they will rather break at any other part than along
the line of union. But although people see the operation constantly
performed and buy liberally of the cement, it will be found that in
nine cases out of ten, the cement proves worthless in the hands of the
purchasers, simply because they do not know how to use it. They are
afraid to heat a delicate glass or porcelain vessel to a sufficient
degree, and they are apt to use too much of the material, and the
result is a failure.

The great obstacles to the junction of any two surfaces are air and
dirt. The former is universally present, while the latter is due to
accident or carelessness. All surfaces are covered with a thin adhering
layer of air, which it is difficult to remove, and which, although
it may at first sight seem improbable, bears a relation to the outer
surface of most bodies different from that maintained by the air a few
lines away. The reality of the existence of this adhering layer of air
is well known to all who are familiar with electrotype manipulation.
It is also seen in the case of highly polished metals which may be
immersed in water without becoming wet. Unless this adhering layer
of air is displaced, the cement cannot adhere to the surface to
which it is applied because it cannot come in contact with it. The
most efficient agent in displacing this air is heat. Metals warmed
to a point a little above 203° F. become instantly and completely
wet when immersed in water. Hence, for cements that are used in a
fused condition, heat is the most efficient means of bringing them in
contact with the surfaces to which they are to be applied. Another
very important point is to use as little cement as possible. When the
surfaces are separated by a large mass of cement we have to depend
upon the strength of the cement itself and not upon its adhesion to
the surfaces which it is used to join; and, in general, cements are
comparatively brittle.

The cement forced out of the joint by pressing the surfaces together
should be removed while the cement is in a fused state or liquid.
This can generally be effected by wiping the surplus off, while after
solidification a certain amount of force has to be used which may
frequently break the joint.

Oil cements, which generally solidify slowly, have the advantage of
being water-proof. In cementing with oil cements, coat the surfaces to
be joined with linseed oil, or, still better, boiled linseed oil, but
in working with resinous cements apply oil of turpentine, spirit of
wine, or a fluid which will readily dissolve the cementing constituent
of the cement.

For cleansing the surfaces from grease and dirt place the articles in
strong lye and rinse off in clean water without touching the surfaces
with the hands. For painted porcelain articles which cannot be placed
in lye, it is recommended to brush the surfaces several times with
carbon disulphide.

PASTES AND MUCILAGES.

_Preparation of paste._ Ordinary paste is prepared either from flour or
starch, and according to the raw material used in its preparation, may,
therefore, be divided into starch and flour paste.

Starch is an indispensable constituent of certain parts of plants, and
plays an important part in the nutrition of the plant. It is chiefly
manufactured from potatoes, Indian corn and grain. Examined under the
microscope, it is seen to be composed of small granules consisting of
layers placed one above the other.

_Starch paste._ In stirring starch with water to a thin paste and
gradually heating it, it will be observed that at a temperature between
140° and 158° F. a peculiar change takes place; the thin milk-white
liquid becomes transparent, opalizes, and at the same time becomes
thickly fluid, in short, the starch is converted into paste. During
this process the separate layers of the starch granules become detached
somewhat in the same manner as an opening bud, whereby they absorb
water, and the peculiar mass, called paste, is formed. That paste is
not a solution is easily proved by the fact that on attempting to
filter starch-paste only water drains off, while the starch remains
upon the filter and gradually dries to a horny mass.

Paste left to itself soon decomposes, especially during the hot season
of the year; it becomes sour through the formation of lactic acid,
butyric acid, acetic acid, and other substances, and loses its adhesive
power.

In preparing paste, the following rules must be especially observed:
Divide the starch in water by constant stirring so as to form a
homogeneous, rather thinly liquid fluid, and then add boiling water
in small portions, stirring constantly. The conversion of the starch
into paste is recognized by the thickening of the entire mass and
the appearance of opalescence, when it is only necessary to add the
required quantity of water to give the paste the desired consistency.

If white lumps are observed, it is an indication that the starch has
not been thoroughly mixed with the water, and that certain portions of
it have remained dry. Paste containing such lumps cannot be applied
with any degree of uniformity, and besides it possesses less adhesive
power. Nothing can be done to remedy the evil except diluting the
paste with a considerable quantity of water and boiling, with constant
stirring, until the mass is perfectly homogenous.

Starch paste prepared in a proper manner possesses great adhesive
power, and, when applied in a thin layer, dries to an almost colorless
coating. Pure starch paste is used for many purposes. It serves not
only for pasting paper, wall paper, etc., but also for sizing tissues,
such as paper-muslin, linen, etc., in order to give them lustre, body,
and, under certain circumstances, greater weight. To increase the
weight of linen, white lead or heavy spar is frequently mixed with the
starch.

_Flour paste._ The principal constituent of flour, besides starch, is
gluten. It is obtained in a pure state by tying flour in a linen bag
and kneading it under water so long as the latter is rendered turbid by
particles of starch. The gluten remaining in the bag is a light-brown,
very tenacious mass, drawing threads between the fingers, and, as
regards its chemical properties, is closely allied to albumen and
caseine. Gluten, like the last-mentioned substances, shows a tendency
to form combinations with lime which gradually solidify, and it can
therefore be used for preparing cements. Like albumen and caseine,
it speedily putrefies if exposed to the air in a moist state, and in
decomposing forms products which have a very unpleasant odor.

Flour paste is prepared in precisely the same manner as starch paste,
but while the latter is white, flour paste, even if prepared from the
best wheat flour, has always a yellow-brown color. As regards adhesive
power it is superior to starch paste, but is less durable.

There are many means to prevent the spoiling of paste. With paste
once dry and kept so, there is no danger of spoiling, but if it
is alternately exposed to dampness and dryness, as for instance
with wall-paper hung on walls not entirely dry, decomposition will
unavoidably take place, and the wall paper will become spotted and fall
off the wall.

Provided either starch or flour paste is protected against drying in,
it can be kept unchanged for a long time by the addition of a small
quantity of carbolic acid.

For hanging wall-paper an addition of alum is, generally speaking, more
suitable than carbolic acid.

In hanging wall-paper the wall is generally first sized with
glue water. By the alum coming in contact with glue an insoluble
leather-like combination is formed, which not only resists
decomposition, but by far surpasses ordinary paste as regards adhesive
power, so that when the paper is to be removed from the wall it has
to be scraped and torn off in small pieces, while that hung without
previous sizing of the wall is readily removed in large pieces.

But alum cannot be used for preserving a glue solution, as it would
cause it to coagulate to a flaky mass. Carbolic acid is, on the
other hand, an excellent means for the purpose, but to prevent its
characteristic empyreumatic odor from making itself too sensibly
felt, no more than about one two-thousandth of the weight of the glue
solution should be added.

_Shoemakers’ paste._ In addition to being cheap, no other paste adheres
as well to leather as the so-called shoemakers’ paste. With it leather
can be secured not only to leather, but also to woven materials, paper,
etc. Though its preparation is very simple, it is connected with some
disagreeable features consisting chiefly in the development of a truly
terrible stench.

The paste is prepared by stirring crushed barley with hot water to
a thick paste and adding small portions of hot water, so that the
temperature of the mass is kept at between 86° to 104° F. In a few
days the mass commences to develop gas, which shows at first no odor,
but soon the development of gas becomes stronger and an acid odor is
perceptible, which in a short time is replaced by a terrific stench
which, as before mentioned, affects the olfactory organs in a most
unpleasant manner.

In consequence of the acid and putrid fermentation the pasty mass
gradually loses its granular condition, and is finally converted into a
homogeneous, thickly fluid mass of a brown color, which draws threads
between the fingers, and possesses great adhesive power. When this is
the case, decomposition, which otherwise would go on until nothing
remained but a watery and acid fluid, is interrupted by lowering the
temperature of the paste by ladling it from the vat or by adding a
small quantity of carbolic acid.

To render the stench developed during the fermentation of the paste
innoxious, the vat in which it is prepared should be provided with
a well-fitting cover, in which is fitted a stovepipe passing into a
chimney connected with a kitchen range or furnace, in which a fire is
frequently burnt.

By kneading shoemaker’s paste together with indifferent substances it
can be used as a cement for various purposes. The substances best
adapted for the purpose are burnt lime slaked to a powder, whiting,
zinc white, pipe clay, ochre, etc.

_Gum arabic._ This gum is an exudation from certain tropical species of
acacia, and consists essentially of arabine, which has the composition
C_{12}H_{11}O_{11}. The best gum arabic is that in the form of very
pale-yellow, brittle pieces; golden-yellow to brownish pieces are not
valued as highly, though they give a solution of considerable adhesive
power.

Gum arabic dissolves in water, but not in alcohol, and therefore can
not be employed for cements in the preparation of which solutions of
resins in spirit of wine are to be used.

There are other products of vegetable life, which are also in commerce,
called gums, but dissolve partly in spirit of wine. To this class
belongs the gum ammoniac mentioned in some receipts for cements. As it
is rather expensive, it is seldom used by itself as a cement.

_Dextrine_ is extensively used in place of gum arabic in printing
wall-papers, for stiffening and glazing cards and paper, for thickening
the colors of calico printers, in making mucilages, etc. It is prepared
by heating starch previously moistened with nitric acid in an oven,
and can also be produced by heating paste with malt extract or very
dilute sulphuric acid. There is a current anecdote which attributes the
discovery of dextrine to a conflagration at a starch factory where one
of the workmen who assisted in quenching the fire observed the gummy
properties of the water which had been thrown over the torrefied starch.

Commercial dextrine forms pale-yellow to dark-brown masses. These
masses dissolve readily in water, and form solutions which, as regards
adhesive power, compare favorably with those prepared from gum arabic.
The mucilage is prepared by simply stirring the pulverized dextrine
with water to a thickly-fluid liquid.

To preserve mucilage unchanged for any length of time, and to
prevent the disagreeable formation of mould upon its surface, it is
recommended to dissolve some salicylic acid in the water to be used for
preparing the mucilage.

Dextrine is usually prepared on a large scale by moistening 10 parts of
starch with 3 parts of water acidulated with 1/100 part of nitric acid.
The mixture is allowed to dry, and is then spread upon trays in layers
about three-quarters of an inch deep in an oven, where it is heated for
about one hour to 239° F. Sometimes large drums revolving over a fire
are used, or, in order to keep up a uniform temperature, the starch is
placed in a copper cylinder suspended in a vessel with oil which is
heated to 356° F. The object of the addition of nitric acid is to allow
the starch to be converted into dextrine at a temperature which would
be inadequate to effect the transformation of starch alone.

Dextrine is also frequently prepared by allowing germinated barley or
malt to act upon starch. Heat 350 to 400 parts of water to about 77°
F., and after adding 5 to 10 parts of dry malt, raise the temperature
to 140° F. Then add 100 parts of starch, and after mixing the whole
thoroughly together, raise the temperature to about 158° F. for twenty
minutes. The mass, which appears at first milky and sticky, will
gradually become as liquid as water by the conversion of the starch
into gum through the action of the malt. To prevent the conversion
of the gum into sugar by the diastase of the malt, the fluid must be
quickly brought to the boiling-point, and, after cooling, filtered
and evaporated to the consistency of syrup. In cooling, the mass
gelatinizes to a jelly, which after drying is hard and brittle.

According to Blumenthal’s method, a drum which can be hermetically
closed, is filled two-thirds full with dry starch flour by means of a
funnel. A stirring apparatus is then set in motion, and the acid which
is contained in a graduated cylinder is sprayed into the drum by means
of a special contrivance.

In a drum 5 feet long and 3¼ feet in diameter, 220 lbs. of potato
starch can be uniformly mixed in 5 minutes with about 9 ozs. of nitric
acid of 40° B., and the drum emptied by opening the slide. Starch thus
treated may be brought into the oven without previous drying.

Heuzé gives the following method: Four and a half pounds of nitric
acid of 1.4 specific gravity together with 300 quarts of water are
mixed with 2,200 lbs. of starch, and boiled to form a mass which,
when exposed to the air becomes dry. It is sometimes effected at 177°
F., but it becomes a paste at 212° to 230° F. The starch changes into
dextrine in an hour or an hour and a half at the most; it is white and
soluble in water.

_Tragacanth, or gum tragacanth_, exudes from _Astragalus verus_, a
tree indigenous to Asia. The term gum is a misnomer, as tragacanth
does not actually dissolve in water nor in spirit of wine, but merely
swells up in water to a soft gelatinous mass. Tragacanth consists of
irregular pieces of a pure white to yellowish color. It is chiefly used
for confectioner’s purposes, though sometimes as a paste for fancy
articles. This variety of gum is found, together with arabine, in the
gum which exudes from cherry, plum, almond, and apricot trees, and
gives the mucilaginous character to the watery decoctions prepared from
certain seeds, such as linseed and quince-seed, and from the root of
marshmallow.

PASTES AND MUCILAGES FOR SPECIAL PURPOSES.

_Starch paste._ Corn starch 8 ozs., cold water ½ pint, boiling water 1
gallon.

Beat up the starch in the cold water until reduced to a creamy
consistence, then pour the mixture into the boiling water and stir
briskly until the white, semi-opaque mass, becomes transparent. Should
it fail to do so, place it over the fire, and boil until the desired
result is obtained, stirring constantly.

_Flour paste._ Wheat flour 4 lbs., cold water 2 quarts, alum 2 ozs.,
hot water ½ pint, boiling water 2 gallons.

Work the wheat flour into a batter free from lumps with the cold
water. Dissolve the alum in the hot water. Then stir the batter into
the boiling water, and if necessary, continue boiling until the paste
thickens into a semi-transparent mucilage, after which stir in the alum
solution. This makes a very fine paste for wall-paper.

_Strong adhesive paste._ Rye flour 2 lbs., cold water 1 quart, boiling
water 3 quarts, pulverized rosin 1 oz.

Make the flour into a batter with the cold water, free from lumps, and
pour into the boiling water. Boil, if necessary, and while hot stir in
the pulverized rosin, a little at a time. This paste is very strong,
and will fasten heavy wall-paper or thin leather. If too thick, thin
with hot water. Never thin paste with cold water.

_Paste that will not sour._ Allow 4 parts by weight of glue to soften
in 15 parts of cold water for some hours, and then heat moderately
till the solution becomes quite clear; then add, while stirring, 65
parts of boiling water. In another vessel stir up 30 parts of starch
paste with 20 parts of cold water, so that a thin, milky fluid without
lumps is obtained. Into this pour the boiling glue solution, stirring
constantly, and keep the whole at the boiling temperature. After
cooling, add 5 to 10 drops of carbolic acid to the paste. Preserve the
paste in closed bottles to prevent evaporation of the water. It will
thus keep good for years.

_Venetian paste._ White or fish glue 4 ozs., cold water ½ pint, Venice
turpentine 2 fluid ozs., rye flour 1 lb., cold water 1 pint, boiling
water 2 quarts.

Soak the 4 ozs. of glue in the cold water for 4 hours. Dissolve over
a water-bath, and while hot stir in the Venice turpentine. Make up
the rye flour into a batter free from lumps with the pint of water,
and pour the latter into the boiling water. Stir briskly, and finally
add the glue solution. This makes a very strong paste, and it will
adhere to a painted surface, owing to the Venice turpentine in its
composition.

_Label paste._ A good paste for attaching labels to bottles may be made
by soaking glue in strong vinegar, then heat to boiling and add flour.
This is very adhesive, and will not decompose when kept in wide-mouthed
bottles.

_Elastic or pliable paste._ Starch 4 ozs., white dextrine 2 ozs., cold
water 10 fluid ozs., borax 1 oz., glycerine 3 fluid ozs., boiling water
2 quarts.

Beat the starch and dextrine into paste with the cold water. Dissolve
the borax in the boiling water, then add the glycerine, and pour
the starch and dextrine mixture into the borax solution. Stir until
it becomes translucent. This paste will not crack, and, being very
pliable, is suitable for paper, cloth, leather and other material where
flexibility is required.

_Mucilage for labels._ Macerate 5 parts of good glue in 20 parts of
water for 24 hours, and to the liquid add 9 parts of rock candy, and
3 parts of gum arabic. The mixture may be brushed upon paper while
lukewarm. It keeps well, does not stick together and adheres firmly to
bottles.

_Mucilage._ A strong aqueous solution of dextrine forms a most adhesive
and cheap mucilage. Dilute alcohol is usually employed as the solvent
where the mucilage is to be used for gumming envelopes, postage stamps,
etc., and in order to facilitate the drying, acetic acid is added to
increase the mobility of the fluid. The strong aqueous solution is
more adhesive than that prepared with alcohol, for the reason that it
contains a greater proportion of dextrine.

To prepare this add an excess of dextrine to boiling water, stir for
a minute or two, allow to cool and settle, and strain the liquid
through a cloth. The addition of a little powdered sugar increases the
glossiness of the dried gum. The sugar should be dissolved in the water
before the dextrine is added.

_According to another formula_, dextrine is mixed with hot water until
a syrupy liquid is obtained. Then add a few drops of oil of cloves, and
cool for use.

_Another formula is as follows_: Dextrine 120 parts, powdered alum 6,
sugar 30, carbolic acid 1, water 300. Mix gradually the dextrine, alum
and sugar with the water, boil to effect solution, and when cold, add
the carbolic acid.

The solubility of dextrine may be enhanced by the addition of a calcium
salt readily soluble in water, the resulting mixture dissolving with
ease in cold water. Calcium nitrate has proved especially suitable for
the purpose. By pouring 1 quart of water over a mixture of 18 ozs. of
dextrine and 7 ozs. of calcium nitrate, a mass of great adhesive power
is immediately obtained.

_Mucilage for postage stamps._ Dextrine 2 parts, acetic acid 1, water
5, alcohol 1. Mix all together.

_Caseine mucilage._ Take the curd of skim milk, wash it thoroughly, and
dissolve it to saturation in a cold concentrated solution of borax.

_Tragacanth mucilage._ Powdered tragacanth 2 drachms, glycerine 12
drachms, water enough to make 20 ozs.

Put the tragacanth in a mortar with the glycerine, and then add the
water. This will produce at once a mucilage of excellent quality.

_Adhesive paste._ Steep 4 ozs. of ordinary gelatine in 16 ozs. of water
until it becomes soft, then dissolve it by the heat of a water bath,
and while still hot pour into a mixture of 2 lbs. of good flour paste
and 1 part of water. Heat the whole to boiling and when thickened
remove from the fire. While cooling add 6 drachms of silicate of soda
and stir the mixture with a wooden spatula. This preparation will keep
good for an indefinite period, and is very adhesive. The addition of 2
drachms of oil of cloves is an improvement.

_Fluid pastes._ I. Gum arabic 10 lbs., sugar 2 lbs., nitric acid 1¾
ozs., water as required.

Dissolve the gum and sugar in the water, then add the acid and heat to
the boiling-point. The resulting paste is liquid, does not mould, and
dries to a transparent layer upon paper. It is especially suitable for
flaps of envelopes, fine bookbinders’ work, etc.

II. Potato starch 10 lbs., water 5 quarts, nitric acid 8 ozs.

Mix the acid and water and pour it on the starch in an earthenware
basin, put the latter in a warm place, and allow it to remain 24 hours,
with occasional stirring. Then boil it until it becomes thickly-fluid
and very transparent. If necessary it should be diluted with water and
filtered through a cloth.

_Sugar and lime paste._ Dissolve 12 parts of white sugar in 36 of
water. Heat the solution to the boiling-point and add 3 parts of slaked
lime. Allow the liquid to stand in a covered vessel for several days,
stirring frequently and, when settled, pour off the supernatant thick
fluid from the excess of lime.

The paste thus obtained has all the properties of gum arabic solution
and dries to a lustrous mass.

_Liquid sugar and lime paste._ Allow 3 parts of glue to swell in 10 to
15 parts of the foregoing paste. Heat the mixture to the boiling-point.
The paste thus obtained does not congeal on cooling and possesses
considerable adhesive power.

By reason of its caustic properties, due to the content of lime, this
paste should not be used for pasting colored materials.

_Pastes for paper and fine fancy articles._ I. Dissolve, with the
assistance of heat, 100 parts of gilder’s glue in 200 of water, and add
a solution of 2 parts of bleached shellac in 10 of alcohol.

II. Dissolve, with the assistance of heat, 50 parts of dextrine in 50
of water, stir solutions 1 and 2 together, strain through a cloth into
a flat prismatic mould, and allow it to congeal. For use, melt a piece
of corresponding size, and dilute the liquid, if necessary, with water.

_Albumen paste._ This is a misnomer, as it contains no albumen. It is
partly decayed gluten from flour, washed with water and then heated to
60° or 68° F., when it ferments and becomes partly fluid. It is then
dried at 77° to 86° F., and is claimed to keep any length of time in a
dry place. Dissolved in twice its weight of water it can be used as a
paste for all purposes.

_Glycerine paste._ Dissolve 2 ozs. of gum arabic and 4 drachms of
glycerine in 6 ozs. of boiling water. This is a good paste for office
use.

_Paste for fixing labels on machines._ Make a paste of rye flour and
glue and add to every pound thereof ½ oz. each of boiled linseed oil
and turpentine. This paste resists damp and thus prevents printed
labels from falling off metallic surfaces.

_Paste for mounting maps._ Stiff rye flour paste is best for this
purpose.

_Paste for fastening paper on tin-foil._ Make a paste by dissolving rye
flour in solution of caustic soda; dilute with water, stirring all the
time. Add to this paste a few drops of Venice turpentine for each ½ lb.
of flour.

_Paste for paper bags._ Add to 3 parts of starch 24 to 30 parts of cold
water. Stir together to a homogeneous mass of about the thickness of
syrup. Pour over this, stirring constantly, boiling water until the
paste is of the required consistency. Stir until nearly cold. Take a
portion of the paste and add to it 6 to 15 per cent. liquefied Venice
turpentine; rub together until a kind of emulsion is formed, then mix
the whole together and work thoroughly.

_Caseine mucilage for photographer’s use._ Separate the caseine from
milk by means of a little tartaric acid, and treat the caseine while
still warm with a solution of 6 parts of borax to 100 parts water,
and warm gently while stirring which will cause the caseine to be
dissolved. Of the borax solution enough should be used to leave only a
little undissolved caseine behind.

_Paste for scrap-books._ Rice starch 1 oz., gelatine 3 drachms, water ½
pint.

Heat, stirring constantly, until the milky fluid becomes thick and
gluey. When the paste is nearly thick put in a bottle closely corked.
It is well to add a few drops of oil of cloves to each bottle.

_Paste for skins._ Pour enough boiling water over 1 lb. of rye flour in
a basin to make a stiff paste, almost as stiff as ordinary dough for
puddings. Stir and beat up well with a stick for three or four minutes,
then cover up and let it stand for two days before using, when it will
be much softer and stick better. Spread thinly and evenly on the back
of the skin with a stiff brush or pad. It will stick firmly and not
crack.

_Strong mucilage_ capable of fastening wood or china and glass together
is made of 3½ ozs. of strong gum arabic solution, to which a solution
of 30 grains of sulphate of aluminium dissolved in ⅔ oz. of water is
added.

_Dextrine mucilage._ I. Dissolve with the assistance of heat 60 parts
of borax in 420 parts of water, add 480 parts of pale yellow dextrine
and 50 parts of glucose, and heat carefully, stirring constantly until
solution is complete, replacing the water lost by evaporation. Strain
through flannel.

The resulting mucilage is quite clear, has great adhesive power, and
dries very quickly. In heating the mixture, great care should be
exercised not to exceed a temperature of 194° F. and not to heat too
long, otherwise the product readily becomes brown and brittle.

II. Dextrine 120 parts, powdered alum 6, sugar 30, carbolic acid 1,
distilled water 300. Gradually mix the dextrine, alum and sugar with
the water, effect solution by boiling and when the solution is cold,
add the carbolic acid.

_Paste for joining leather to pasteboard._ Dissolve 50 parts of strong
glue with a little water at a gentle heat, then add a small quantity of
Venice turpentine, and next a thick paste made with 100 parts of starch
in water. Apply quickly when cold.

_Another formula_ for a similar paste is as follows: Rye whisky 2
pints, water 1 pint, powdered starch 4¼ ozs., good glue 1¼ ozs., Venice
turpentine 1¼ ozs. Mix the whisky and water together, then stir in the
starch and make a thick paste. Separately dissolve the glue in an equal
weight of water, and mix the Venice turpentine therein, mix thoroughly,
and then compound this mixture with the thick paste by constantly
stirring until all is well incorporated.

_Paste for attaching labels to polished nickel._ Dissolve 400 parts by
weight of dextrine in 600 parts of water, and add 20 parts of glycerine
and 10 parts of glucose. Heat the mixture to 194° F.

_Another formula_ is as follows: Mix 400 parts by weight of dextrine
with water, and add 200 parts of water together with 20 parts of
glucose and 10 parts of aluminium sulphate.

_Mucilage for attaching labels to tin._ I. Shellac 8 parts, borax 4
parts, water 60 parts. Boil until the shellac is dissolved.

II. To 2 parts of dammar varnish add 8 parts of tragacanth mucilage.

III. An excellent mucilage for the purpose consists of starch paste to
which a small quantity of Venice turpentine has been added.

IV. Make a paste of corrosive sublimate 2½ parts, wheat flour 200,
absinthe 100, tansy 50, water 3000. This mucilage is useful for vessels
kept in a damp place.

_Mucilage for office use._ Gum arabic 100 parts, aluminium sulphate
6 parts, glycerine 10, dilute acetic acid 20, distilled water 140.
Dissolve, in a wide-mouthed glass bottle, the gum arabic in cold
distilled water, stirring frequently. Let the solution stand 2 or 3
days, then add the glycerine, later on the dilute acetic acid and
finally the aluminium sulphate. Strain through a hair sieve, allow to
clarify, and decant from the sediment.

_Glycerine paste for office use._ Dissolve 4 ozs. of gum arabic and 8
drachms of glycerine in 12 ozs. of boiling water.

_Clean and durable paste._ Dissolve 5 ozs. of gum arabic in 4 quarts
of warm water, and thicken to a paste with wheat flour. Then add a
solution of alum and sugar of lead, 3 ozs. of each in water. Heat the
mixture and stir it until it is about to boil, and then cool it. If too
thick, add gum solution.

_Banknote or mouth glue._ Dissolve by the aid of heat a fine quality
of glue or gelatine with about a quarter or one-third of its weight of
brown sugar, in as small a quantity of water as possible. Then when
perfectly liquid cast the mixture into thin cakes on a flat surface
very slightly oiled, and when cold cut up into pieces of convenient
size. When required for use moisten one end. A piece of this glue kept
in the desk will be found very convenient for many purposes.

_Paste for cardboard._ Dissolve 3½ ozs. of best French glue in 6½ ozs.
of water by soaking and heating. Then add a solution of ½ drachm of
shellac in 3½ drachms of alcohol and stir as long as the solution is
warm. Next dissolve 2 drachms of dextrine in 1¾ ozs. of alcohol and
14 drachms of water, stir, and place the vessel in warm water until
solution is complete. Mix this solution with that of the glue, and pour
the whole into a suitable vessel, in which it may solidify. When wanted
for use cut off a small piece and liquefy it by warming.

_Paste for attaching cloth or leather to table tops._ Wheat flour 1
lb., powdered rosin 2 tablespoonfuls, powdered alum 1 tablespoonful.
Heat and stir to a stiff consistency.

_Caseine mucilage._ Separate the caseine from milk with a little
tartaric acid, and treat the caseine while still warm with a solution
of 6 parts borax to 100 parts water and warm gently while stirring,
which will cause the caseine to be dissolved. Of the borax solution
enough should be used to leave only a little undissolved caseine behind.

_Very adhesive paste which may be used for wood and parchment._ Gum
arabic 60 parts, fine wheat starch 45, sugar 15. Dissolve the gum in
as much water as is required for boiling the quantity of paste to be
made. Then add the starch and sugar and boil it in a vessel suspended
in boiling water until the mixture is clear and has the consistency of
liquid tar. Keep in a well-closed vessel protected from mould by the
addition of a few drops of oil of cloves.

_Paste for pads._ Glue 4 parts by weight, glycerine 2, linseed oil ½,
sugar 4, aniline dye sufficient to color. Soften the glue by soaking in
cold water, then dissolve together with the sugar in the glycerine by
the aid of heat over the water-bath, then add the dye and stir in the
oil. Use the paste hot.

_Paste for fastening paper on tin-foil._ Make a paste by dissolving
rye flour in a solution of caustic soda; dilute with water, stirring
constantly. Add to this paste a few drops of Venice turpentine for each
½ lb. flour used. This paste adheres to all kinds of metal, tin-foil,
glass, etc.

_Paste for attaching labels to glass, porcelain, and metal._ Gum
arabic 15 parts, pulverized tragacanth 7½, glycerin 45, thymol 0.3,
alcohol 3¾, water 120. Dissolve the gum arabic in 15 parts of water and
triturate the tragacanth with 30 parts of water. Mix the two fluids and
strain. Then add the glycerine and finally the thymol dissolved in the
alcohol.

_Preparation of arabol-gum._ Mix intimately 44 lbs. of wheat starch
with 176 lbs. of water. Bring the mass into a water-bath, mix it with
a solution of 4.4 lbs. of oxalic acid in 44 lbs. of water and heat
for four hours at 194° F., stirring frequently. The conversion of the
starch is as a rule effected during this time, but should such not be
the case, continue heating, constantly replacing the evaporated water,
until the mass is clear and liquid. While still hot, neutralize the
mass with marble dust, allow to settle, filter, and evaporate the clear
solution in a water-bath to a solid gum containing about 15 per cent.
of water.

_Preparation of an adhesive substance from desaccharized beet-root
slices_ (German patent 96316 f. G. Eichelbaum). The insoluble
metarabin contained in the slices is converted into soluble arabin by
treating the slices under pressure with hot aqueous sulphurous acid or
with aqueous solutions of the bisulphites of the alkalies or alkaline
earths.

According to a later patent (German patent 121422 f. Fabrik
Bettenhausen Marquart and Schulz), the insoluble metarabin is converted
into soluble arabin by heating the desaccharized beet-root slices with
phosphoric acid and water. According to a supplement to this patent
(122048), conversion is effected by heating the slices with aqueous
solutions of organic acids and phenols, or the acid salts of oxalic,
tartaric or phosphoric acids.

INDEX.

Acid calcium phosphate, 120

—— —— —— crystallization of, 125, 126

—— —— —— formation of, 121-124

—— sodium sulphate, use of, in drying glue, 72, 73

Acidity, determination of, in glue, 205, 206

Acids, dilute, effect of, on glue solution, 7

Adamson, Wm., method of, for removing hydrocarbons from substances
which have been treated therewith, 84-86

—— —— method of, for treating substances with hydro carbon vapor for
the purpose of extracting oils, fats, etc., 79-82

—— —— method of, for treating substances with liquid hydrocarbons for
the purpose of extracting oils, fats, etc., 82-84

—— —— and Simonis, Chas. F. A., apparatus of, for extracting bones
with benzine, 76-79

Adhesive paste, 264

Adulterations of glue, determination of, 214, 215

Agar-Agar, 12, 201, 202

Air-bladders, 16, 41

—— bleaching glue in the, 141

—— drying the cakes of glue in the, 64

Alabaster, 244

—— cement for, 242

Albumen paste, 265, 266

—— —— use of, for clarifying glue liquor, 54

Alum cement, 228

—— —— effect of, on glue solution, 7

—— —— use of, for clarifying glue liquor, 54

—— —— —— —— preserving paste, 257

Amber, resinous cement for, 229

American cement for jewelers, 252

American glue, analysis of, 207

Ammonium sulphate, use of, in drying glue, 72, 73

Animal charcoal, bleaching glue with, 142

—— —— bones for the manufacture of, 107

—— —— carbonization of bones for, 108-112

—— —— decolorizing glue liquor with, 55

—— —— manufacture of, 112, 113

—— —— yield of, 113

—— skin, constitution of, 17, 18

Antiseptics for the preservation of glue-stock, 30

Arabin, conversion of metarabin into, 271

Arabol-gum, preparation of, 270

Ash, burning bones to, 117-119

Bacteriology, use of gelatine in, 194

Banknote glue, 269

Barium chloride, effect of, on glue solution, 7

Basic calcium phosphate, 120

Beet-root slices, desaccharized, preparation of an adhesive
substance from, 270, 271

Belgian retort-furnace for the carbonization of bones, 109-112

Benzine, extracting fat from bones with, 76-92

Billiard balls, compound for, 155, 156

Bleaching glue, methods of, 141-145

—— —— stock, 55, 56

Blood, fresh, use of, for clarifying glue liquor, 54

Blumenthal’s method of preparing dextrine, 260, 261

Boiler for glue boiling, 44

Boiling bones, 74, 75

—— —— duration of, 45

—— —— or cooking glue, 44-52

Bone ash, composition of, 119

—— —— conversion of, into a coarse powder, 119

—— —— decomposition of, by sulphuric acid, 119-125

—— —— kiln for, 117-119

—— —— preparation of, 117-119

—— —— yield of, 119

—— cartilage, composition of, 32

—— cement for, 230

—— crusher, 36

—— gelatine, 170-180

—— —— modern process of preparing, 179, 180

—— -glue, manufacture of, 74-116

—— meal, glue and fat, simultaneous utilization of bones for, 104-113

—— -mill, Crosskill, 36

—— raw materials, 16

—— size, 159, 160

Bones, absorption of sulphurous acid by, 92

—— Adamson and Simonis’ apparatus for extracting, 76-79

—— and cartilages, 31-39

—— apparatus for extracting the fat from, with benzine, 76-94

—— Belgian retort-furnace for the carbonization of, 109-112

—— boiling of, 74, 75

—— burning of, to ash, 117-119

—— buying of, 32

—— carbonization of, 108-112

—— constitution of, 32

—— crushed, sorting of, 36, 37

—— crushing or grinding of, 33-36

—— extraction of, 76-94

—— —— —— phosphates from, 115

—— fatty matters in, 32

—— for the manufacture of animal charcoal, 107

—— honey-combed, 39

—— Leuner’s apparatus for extracting, 90-92

—— lime bath for, 37

—— products obtained in the distillation of, 112

—— Seltsam’s apparatus for extracting, 84-86

—— —— apparatus for extracting, improved by Th. Richter, 88-90

—— simultaneous utilization of, for fat, bone-meal and glue, 104-113

—— —— utilization of, for fat, glue and calcium phosphate, 113-116

—— sorting of, 32, 33, 104, 105

—— sulphurous acid for extracting, 92-94

—— treatment of, with high pressure steam, 105-107

—— utilization of the liquor obtained in the treatment of, with
hydrochloric acid, 125-127

—— value of, 32

—— waste of, from the preparation of tinned provisions, 19

Bookbinder’s glue, 12

—— size, 160

Book isinglass, 197

Boric acid, preservation of glue-stock with, 30

Bottles, cracked, cement for, 240, 241

Bouillon tablets, 12

Brazilian isinglass, 199, 200

Briers, D. J., process for the preparation of bone gelatine
employed by, 171-179

Brochette, 43

Brushmaker’s cement, 251

Bullock’s feet, 18

—— hide, waste of, 18

—— leather, 30

Burning bones to ash, 117-119

Cakes, cutting glue into, 57-64

—— drying the, 64-73

—— machines for cutting the jelly into, 60-64

—— shape of, 57, 58

—— tools for cutting the jelly into, 59

Calcium chloride, 116

—— metaphosphate, 120, 127

—— phosphate, 115

—— —— fat and glue, simultaneous utilization of bones for, 113-116

Calf leather, 30

—— skin waste, 18

Calves’ feet, 30

—— heads, 18, 30

Carbolic acid, preservation of glue-stock with, 29

—— —— use of, for preserving paste, 257, 258

Carbon disulphide, use of, for extracting bones, 76

Cardboard, paste for, 269

Cartilage, 1

—— conversion of, into glue, 94-104

—— drying of, 114

—— preservation of, 114

—— treatment of, with high-pressure steam, 98

—— yield of glue from, 115

Cartilages and bones, 31-39

Caseine cement which can be kept for a long time, 239

—— cements, 237-240

—— mucilage, 264

—— —— for photographer’s use, 266

—— ordinary technical, preparation of, 238, 239

—— pure, preparation of, 237, 238

Castings, cement for filling in defects in, 246

Cattle, pieces of hide from the lower parts of the limbs of, 30

Cayenne isinglass, 199, 200

Cellular tissue, 1

Celluloid, cement for, 252

Cement resisting acids, 248

—— —— —— very high temperatures, 248

Cements, caseine, 237-240

—— chemical nature of, 219

—— classification of, 218-223

—— for chemical apparatus, 247-249

—— —— —— —— special purposes, 249-252

—— glue and starch, 222, 223

—— glycerine, 242

—— gypsum, 244, 245

—— how to use, 252-255

—— iron, 245-247

—— lime, 223, 243, 244

—— oil, 219, 220, 224-229

—— pastes and mucilages, preparation of, 224-271

—— resinous, 220, 221, 229-233

—— resisting high temperatures, 246

—— rubber and gutta-percha, 222, 233-237

—— water glass, 240-242

Chalk, 243

Charcoal, animal, bleaching glue with, 142

—— —— bones for the manufacture of, 107

—— —— carbonization of bones for, 108-112

—— —— manufacture of, 112, 113

—— —— yield of, 113

—— mixing calcium phosphate with, 124

Chemical apparatus, cements for, 247-249

Chinese isinglass, 201, 202

Chlorbarium, soaking hides in, 20

Chloride of lime, bleaching glue-stock with, 55

Chlorine, bleaching glue with, 141

Chondrin, chemical composition of, 5, 6

—— conversion of, into glutin, 6

—— formation of, 3

—— properties of, 5

—— pure, preparation of, 5

Chrome glue, 153

Clarifying glue liquor, 52-56

—— —— —— apparatus for, 98

—— —— —— vats, 53

Clay crucibles, cracked, cement for, 243

Clearness of glue, definition of, 53

Clock faces, white enameled, cement for, 230

Cloth, cement for, 252

—— paste for attaching, to table tops, 269

Colle franche, 43

Cologne glue, 148

Color mixtures, glue for, 11

—— of glue, definition of, 53

Colored gelatine, 181, 182

Coloring glue, 156

—— matters for gelatine, 181, 182

—— substances, removal of, from glue liquor, 54-56

Combs, hard rubber, cement for, 236

Common salt, effect of, on glue solution, 7

Constitution of glue, 3-6

Conversion of cartilage into glue, 94-104

Cooking, duration of, 44

—— or boiling glue, 44-52

Cooling boxes, 100

—— glue liquor, 100

Corium, 1, 17

Court-plaster, 12, 184, 185

Cox, J. and G., process for the manufacture of gelatine patented
by, 166, 167

Crockery, cement for, 236, 237

Crosskill bone mill, 36

Crucibles, cement for, 243

Crude glue, definition of, 3

—— —— preparation of, 43

Culinary purposes, glue for, 12-14

Dark steam glue, 152

Devoulx, cutting apparatus invented by, 62-64

Dextrine mucilage, 267

—— —— preparation of, 259-261

Diamond cement, 229

Distillation of crude phosphorus, 133-135

—— —— phosphorus, 127-132

Drying, acceleration of, 72, 73

—— cakes of glue, 64-73

—— galleries, 68-71

—— house, modern, 71, 72

Drying room, 65

—— —— regulating the temperature of the, 67, 68

East India isinglass, 199

Elastic cement, 234

—— gutta-percha cement, 236

—— masses, glue for, 14

—— paste, 263

Electric furnace for the manufacture of phosphorus, 138-140

Electrical apparatus, cement for, 251, 252

Emery paper, use of glue in the manufacture of, 12

Epidermis, 17

Epsom salt, behavior of glue solution towards, 7

—— —— use of, in drying glue, 72, 73

Evaporating pan, open, 98-100

—— pans, 124

Evaporators, spiral, 100, 101

Extraction of bones, 76-94

Fabrics, water-proofing of, 161-163

Fancy articles, fine, paste for, 265

Fans, gelatine veneers for, 15

Fat, bone meal and glue, simultaneous utilization of bones
for, 104-113

—— extraction of, with benzine, 76-92

—— —— —— hydrocarbon vapors, 79-82

—— —— —— liquid hydrocarbons, 82-84

—— glue and calcium phosphate, simultaneous utilization of
bones for, 113-116

Fertilizers, utilization of liquors for, 116

Fining, gelatine for, 182

Fish bladders, 1

—— —— glue, 202-204

—— —— —— points to be observed in the manufacture of, 41, 42

—— —— —— raw materials for, 41, 42

—— scales, 16, 42

—— —— preparation of glue from, 203

Fleck’s kiln for burning bones, 118, 119

—— process of accelerating the drying of glue, 72, 73

Flour paste, 256-258, 261, 262

Fluid pastes, 264, 265

Foils, gelatine, 15, 185, 186

Formaldehyde, preservation of glue-stock with, 29, 30

Forming or moulding the glue, 56-64

Formo-gelatine, 193, 194

French mastic, 227

—— putty, 225

Friedberg’s apparatus for clarifying glue liquor, 98

—- —— —— conversion of cartilage into glue, 94-97

Furnace, electric, for the manufacture of phosphorus, 138-140

Galley furnace, 128, 129

Galvanized iron-wire netting, 66

Gelatin, pure, preparation of, 4

Gelatine and glycerine, compound of, 12

—— and products prepared from it, manufacture of, 165-195

—— artificial silk from, 195

—— capsules, 14, 184

—— colored, 181, 182

—— constitution of, 165

—— Cox’s process for the manufacture of, 166, 167

—— foils, 15, 185, 186

—— for fining purposes, 182

—— for photographic printing and photographic purposes in
general, 183, 184

—— Jullion and Pirie’s process for the preparation of, 38

—— Nelson’s process for the manufacture of, 166

—— preparation of, from ordinary glue, 182, 183

—— substitute for, 203, 204

—— Swinborne’s improved patented process for the preparation of, 167

—— testing of, 205-217

—— veneers, 15, 186-193

—— yielding tissues, 1

German isinglass, 200

Gilder’s glue, 150

Glass, cement for, 230, 233, 239, 241, 243, 245

—— —— for attaching metal letters to, 249

—— —— —— —— —— to metal, 251

—— mastic cement for, 232

—— oil cement for, 228

—— paper, use of glue in the manufacture of, 12

—— paste for attaching labels to, 270

—— plates, gelatinizing liquors upon, 58, 59

—— upon glass, cement for, 230

—— —— metal, cement for, 230

Glauber’s salt, use of, in drying glue, 72, 73

Gloves, waste from the manufacture of, 43

Glue, acceleration of the drying of, 72, 73

—— addition of mineral substances to, 149

—— American, analysis of, 207

—— and starch cements, 222, 223

—— as a binding agent, 11

—— —— —— joining medium, 10, 11

—— banknote or mouth, 269

—— boiler, Terne’s, 51, 52

—— boiling, boiler for, 44

—— —— convenient apparatus for, 46, 47

—— —— in open jacketed pans, 49, 50

—— —— or cooking, 44-52

—— —— with steam, boiler for, 47-49

—— chemical composition of, 8

—— chrome, 153

—— clearness of, 53

—— Cologne, 148

—— color of, 53

—— coloring of, 156

—— constitution of, 3-6

—— conversion of cartilage into, 94-104

—— cooking, process of, 51

—— crude, definition of, 3

—— —— preparation of, 43

—— cutting the, into cakes, 57-64

—— deduction of the quality of, from indirect properties, 207, 208

—— determination of acidity in, 205, 206

—— —— of adulterations of, 214, 215

—— —— of glutin in, 206, 207

—— —— of moisture in, 205

—— different varieties of, and their preparation, 146-164

—— drying cakes of, 64-73

—— —— room for, 65

—— factory, location of a, 21

—— —— manner of carrying on the work in a, 26-30

—— fat and bone-meal, simultaneous utilization of bones for, 104-113

—— for attaching leather to metal, 153

—— —— culinary and medicinal purposes, 12-14

—— —— elastic masses and as a partial substitute for rubber, 14

—— —— fancy articles, 14, 15

Glue joints in leather driving belts, 163

—— —— —— leather, paper, etc., 153, 154

—— —— —— parchment paper in making sausage skins, 154, 155

—— formation of, 6

—— from various materials, external characteristics of, 6, 7

—— gilder’s, 150

—— holding power of, 147, 148

—— how to make and use, 147

—— in animal organism, 2

—— —— sizing, 12

—— inferior qualities of, 12

—— joiner’s, 146

—— Kissling’s results in testing, 215

—— liquid, 151, 152

—— liquor, apparatus for clarifying, 98

—— —— clarifying the, 52-56

—— —— concentration of, 50

—— —— cooling of, 100

—— —— decolorizing of, with animal charcoal, 55

—— —— instrument for measuring the percentage of glue in, 103

—— measuring the percentage of, in glue liquor, 103, 104

—— methods of bleaching, 141-145

—— moulding or forming of, 56-64

—— nature of, 1-9

—— nets for drying, 66, 67

—— ordinary, preparation of gelatine from, 182, 183

—— parchment, 150

—— Paris, 150, 151

—— patent, 150

—— practical testing of, 215-217

—— principal substances employed as raw material for, 16

—— properties of, and its behavior towards other substances, 6-9

—— raw materials and their preparation for the manufacture of, 16-38

—— results obtained by comparative experiments in testing, 209, 210

—— Russian, 149, 150

—— size, 150

—— solution, behavior of, towards salts, 7, 8

—— steam, 152

—— stock, bleaching of, 55, 56

—— —— dry-limed, 19

—— —— dry, uncured, or salted, 19

—— —— green-limed, 19

—— —— green-salted, 19

—— —— influence of the age of animals on the product from, 20

—— —— limed, washing of, 21-26

—— —— notes in reference to judging, 19, 20

—— —— preparation of, 21-38

—— —— preservation of, 29

—— —— sheds for, 26

—— —— transformation in boiling the, 2

—— —— washer, 22-26

—— substitute for, 203, 204

—— transition stages of, 2

—— uses of, 10-15

—— testing of, 205-217

—— tungstic, 155

—— water-proof, 160

—— yield of, from cartilage, 115

—— —— —— from tannery waste, 18

—— -yielding substance, production of, 2

—— —— tissues, 1

Glutin, conversion of chondrin into, 6

—— determination of, in glue, 206, 207

—— formation of, 3

—— properties of, 4, 5

—— pure, preparation of, 4

Glycerine and glycerine cements, 242

—— —— litharge cement, 242

—— paste, 266

—— —— for office use, 268

—— properties of, 242

Glycocoll, 6

Goat leather, 31

Gray lime, 28

Green waste, liming of, 26, 27

Gum tragacanth, 261

Gutta-percha and rubber cements, 222, 233-237

Gypsum, 244

Gypsum cements, 244, 245

Hager’s diamond cement, 229

Hard rubber cement, 234

—— combs, cement for, 236

Hare skins, 18, 31

Hartshorn, 1

Hayes, S. Dana, analysis of American glue by, 207

Heat-resisting cement, 245

Hectograph mass, 14, 163, 164

Heuzé’s method of preparing dextrine, 261

Hide, transformation in drying the, 2

Hides for glue-stock, classification of, 30, 31

—— soaking of, in chlorbarium, 20

Hoeveller, W. A., apparatus for drying glue invented by, 68-71

—— glue-stock washer of, 22-26

Hog skins, 18

Hollander, 39

Horn, cement for, 232

—— piths, 19

Horses’ hoofs, cement for, 236

Hudson Bay isinglass, 199

Hydraulic works, cement for, 241

Hydrocarbon vapors, extraction of fats, oils, etc., with, 79-82

Hydrocarbons, liquid, extraction of fats, oils, etc., with, 82-84

—— removal of, from substances, 84-86

Hydrochloric acid, treatment of bones with, 37

—— —— utilization of the liquor obtained in treating bones
with, 125-127

Ichthyocolle Française, 200, 201

Irish moss, 202

Iron and stone, cement for, 245

—— cement for, 245, 246

—— cements, 245-247

—— pipes, fire-proof cement for, 246

—— pots, cracked, cement for, 246

—— water tanks, cement for, 246

Isinglass, adulteration of, 196, 197

—— and its substitutes, 196-204

—— chemical composition of, 8

—— preparation of, in Russia, 197, 198

—— sources of, 196

—— spurious, 196

—— substitute for, 203, 204

Isinglassine, 201

Ivory, cement for, 230

Jeffrey’s marine glue, 235

Jelly, definition of, 3

—— effect of tannin on, 8

—— machines for cutting the, into cakes, 60-64

—— properties of, 7

—— tools for cutting the, into cakes, 59

—— transformation in boiling the, 2

Jennings’ method for the preparation of fish glue, 202, 203

Jewelers, American cement for, 252

—— cement, 252

Joiners, cement for, 243

—— glue, 146

Jullion and Pirie’s process for the preparation of gelatine, 38

Kid leather, waste from paring, 31

Kiln for burning bones, 117-119

Kissling’s results in testing glue, 215

Knapsack leather, 31

Knife handles, cement for, 231

Label paste, 263

Labels, mucilage for, 263

—— paste for attaching, to glass, porcelain and metal, 270

—— —— for attaching, to polished nickel, 268

—— —— for attaching, to tin, 268

Lamb leather, 31

Leaf isinglass, 197

Leather, cement for, 235, 237

—— driving belts, glue for joints in, 163

—— for glue-stock, classification of, 30, 31

—— glue for, 153, 154

—— —— —— attaching, to metal, 153

—— paste for attaching, to table tops, 269

—— —— —— joining, to pasteboard, 267, 268

—— skins, actual, 17

—— waste, 39-42

—— —— comminution of, 39, 40

Leucine, 6

Leuner’s apparatus for extracting bones, 90-92

Lime and glue cement, 244

—— —— sugar paste, 265

—— bath for bones, 37

—— cements, 223, 243, 244

—— milk of, preparation of, 26, 27

—— precipitation of, by oxalic acid, 54

—— slaked, effect of, on glue solution, 7

—— testing of, 27, 28

Limed glue-stock, washing of, 21-26

Liming green waste, 26, 27

—— waste, 20

Linseed oil and clay cement, 248

—— —— —— manganese cement, 248

Lipowitz’s method of testing glue, 208, 209

Liquid fining gelatine, 182

—— glue, 151, 152

—— sugar and lime paste, 265

Litharge cement, 225

Magnesium sulphate, 116

Manufacture of bone-glue, 74-116

—— —— gelatine, and products prepared from it, 165-195

—— —— phosphorus, 117-140

—— —— skin glue, 43-73

Maps, paste for mounting, 266

Marble, cement for, 242, 251

—— —— for attaching metal letters to, 249

—— oil cement for, 228, 229

Marine glue, 234, 235

Matches, use of glue in the manufacture of, 11

Mastic, 226, 227

—— cement, 226, 227

Medicinal purposes, glue for, 12-14

Meerschaum, cement for, 239

Meta-gelatin, 7

Metal, cement for attaching wood, glass, etc., to, 251

—— glue for attaching leather to, 153

—— letters upon glass, cement for, 230, 249

—— paste for attaching labels to, 270

Metals, cement for, 239

—— —— for uniting, 241

Metarabin, conversion of, into arabin, 271

Mica, cement for, 231, 232

Milk of lime, preparation of, 26, 27

Moisture, determination of, in glue, 205

Mother-of-pearl, glue imitations of, 15

Moulding boxes, 56

—— or forming the glue, 56-64

—— refined phosphorus, 135-137

Mouth glue, 269

Mucilage, 263, 264

—— caseine, 264

—— —— for photographers’ use, 266

—— dextrine, 267

—— for attaching labels to tin, 268

—— —— labels, 263

—— —— office use, 268

—— —— postage stamps, 264

—— preservation of, 259, 260

—— strong, 267

—— tragacanth, 264

Mucilages and pastes, 255-271

—— —— —— for special purposes, 261-271

—— —— pastes and cements, preparation of, 224-271

Muratori and Landry’s method of water-proofing fabrics, 162, 163

Muzmann and Krakowitzer’s method of water-proofing fabrics, 162, 163

Nature of glue, 1-9

Nelson, G., process of, for the manufacture of gelatine, 166

Nets for drying glue, 66, 67

Netting, metallic, 66

—— twine, 66, 67

Neutral potassium tartrate, behavior of glue solution towards, 7

New York isinglass, 198

Nickel, polished, paste for attaching labels to, 268

North American isinglass, 198

Office use, glycerine paste for, 268

—— —— mucilage for, 268

Oil cements, 219, 220, 224-229

Oils, extraction of, with hydrocarbon vapors, 79-82

—— —— —— with liquid hydrocarbons, 82-84

Ornaments, indestructible mass for, 155

Osseine, 1

Oxalic acid, effect of, on glue solution, 7

—— —— precipitation of lime by, 54

Pads, paste for, 270

Paget’s mastic, 227

Pale steam glue, 152

Pan, open evaporating, 98-100

Pans, evaporating, 124

—— open jacketed, 49, 50

—— vacuum, 101-103

Paper bags, paste for, 266

—— colored, use of glue in the manufacture of, 11

—— glue for, 153, 154

—— hangings, glue in the manufacture of, 11

—— paste for, 265

—— —— —— fastening, on tin-foil, 266, 270

Parchment glue, 150

—— paper, glue for, in making sausage skins, 154, 155

—— scraps, 18

Paris glue, 150, 151

Paste, adhesive, 264

—— albumen, 265, 266

—— clean and durable, 268, 269

—— elastic or pliable, 263

—— fluid, 264, 265

—— for attaching cloth or leather to table tops, 269

—— —— —— labels to glass, porcelain and metal, 270

—— —— —— —— to polished nickel, 268

—— —— cardboard, 269

—— —— fastening paper on tin foil, 266, 270

—— —— joining leather to pasteboard, 267, 268

—— —— mounting maps, 266

—— —— pads, 270

—— —— paper and fine fancy articles, 265

—— —— —— bags, 266

—- —— scrap-books, 266, 267

—— —— skins, 267

—— glycerine, 266

—— —— for office use, 268

—— label, 263

—— preparation of, 255

—— preservatives for, 257

—— rules to be observed in the preparation of, 256

—— strong adhesive, 262

—— sugar and lime, 265

—— that will not sour, 262

—— Venetian, 262

Paste-board, paste for joining leather to, 267, 268

Pastes and mucilages, 255-271

—— —— —— for special purposes, 261-271

—— mucilages and cements, preparation of, 224-271

Patent glue, 150

Patriarch isinglass, 197

Permanent white, addition of, to glue, 149

Petroleum, cement to withstand the action of, 231

—— lamps, cement for, 231

Phosphates, extraction of, from bones, 115

Phosphorus, crude, composition of, 131, 132

—— —— distillation of, 133-135

—— —— purification of, 132

—— distillation of, 127-132

—— galley furnace for distilling, 128, 129

—— loss of, 132

—— manufacture of, 117-140

—— —— of, with the assistance of electricity, 138-140

—— operations in the preparation of, 117

—— refined, moulding of, 135-137

—— refining and purifying of, 132-135

—— receivers for, 129

—— removal of, from the receivers, 131

—— residue in the manufacture of, 127

—— sticks, mode of forming, 135-137

—— storing of, 138

Photographers, caseine mucilage for 266

Photographic printing, gelatine for 183, 184

Photo-lithography, use of glue in, 14

Pierres de mastic, 226, 227

Pipes exposed to a red heat, cement for tightening joints of, 241

Plaster of Paris, 244

—— —— —— cement, universal, 245

—— —— —— statues, cement for, 244, 245

Pliable paste, 263

Porcelain, cement for, 231, 239, 240, 241, 243, 245

—— oil cement for, 229

—— paste for attaching labels to, 270

—— sulphur cement for, 232, 233

Postage stamps, mucilage for, 264

Potassium carbonate, behavior of glue solution towards, 7

Printing rollers, compositions for, 157

Putty, 224, 225

Quick lime, 243

Rabbit skins, 18, 31

Rag-engine, 39

Raw materials and their preparation for the manufacture of glue, 16-38

—— —— collection and buying of, 16

—— —— division of, 16

Receivers for collecting phosphorus, 129

—— —— removal of phosphorus from the, 131

Red lead cement, 225

Resinous cements, 220, 221, 229-233

Retort-furnace, Belgian, for the carbonization of bones, 109-112

Retorts, 127, 128

Rochelle salts, behavior of glue solution towards, 7

Rubber and gutta-percha cements, 222, 233-237

—— cement for, 250

—— —— —— chemical apparatus, 248, 249

—— glue as a partial substitute for, 14

Russia, preparation of isinglass in, 197, 198

Russian glue, 149, 150

—— isinglass, 197, 198

—— steam glue, 152

Sahlstrom’s process for preparing a substitute for isinglass, gelatine
and glue, 203, 204

Sal ammoniac, effect of, on glue solution, 7

Saltpetre, effect of, on glue solution, 7

Salts, behavior of glue solution towards, 7, 8

Samovey leaf isinglass, 197

Sandpaper, use of glue in the manufacture of, 12

Sausage skins, glue for parchment paper in making, 154, 155

Scheibler’s cement for chemical apparatus, 249

Schneible, J., machine for cutting the jelly into cakes invented
by, 60-62

Scrap-books, paste for, 266, 267

Selenite, 244

Seltsam’s apparatus for extracting bones, 84-86

—— —— for extracting bones improved by Th. Richter, 88-90

Serbat’s mastic, 227, 228

Seubert’s apparatus for moulding phosphorus, 135, 136

Sheds for glue-stock, 26

Sheep leather, 31

—— skin waste, 18

Shell lime, 28

Shoemakers’ paste, 258, 259

Siberian purse isinglass, 197

Sieve for sorting crushed bones, 36, 37

Silicate of soda, 240

Silk, artificial, from gelatine, 195

Sinews, 1

Size, 157-160

—— glue, 150

Sizing, glue in, 12

Skin gelatine, 166-170

—— —— modern process of preparing, 167-170

—— glue, classification of operations in the manufacture of, 43

—— —— manufacture of, 43-73

—— -like raw materials, 16

Skins, paste for, 267

—— steeping of, 18

—— used for packing, use of, for glue, 19

Sodium carbonate, behavior of glue solution towards, 7

Soft putty, 225

—— rubber cement, 233, 234

Sounds, 41

Spiral evaporators, 100, 101

Stamping mill for crushing bones, 34, 35

Staple isinglass, 197

Starch and glue cements, 222, 223

—— paste, 255, 256, 261

Steam, apparatus for boiling glue with, 47-49

Steam boiler cement, 250

—— glue, 152

—— high-pressure, treatment of bones with, 105-107

—— pipes, cement for, 250, 251

—— —— oil cement free from lead for, 228

—— —— —— cements for, 228

Steaming bones, 75, 76

Stephenson’s oil cement, 228

Stick mastic cement, 232

Stone lime, 28

Stove plates, cracked, cement for, 246

Stoves, black cement for, 246

Stratena, 252

Straw, use of, as a filter, 44

Sugar and lime paste, 265

Sulphate of alumina, use of, for clarifying glue liquor, 54

—— —— baryta, addition of, to glue, 149

Sulphuric acid, decomposition of bone ash by, 119-125

Sulphurous acid, absorption of, by bones, 92

—— —— bleaching glue with, 143-145

—— —— glue-stock with, 55, 56

—— —— dilute, treatment of bones with, 38

—— —— generation of, 93, 94

—— —— process for extracting bones, 92-94

—— —— solution, apparatus for the production of, 143, 144

Surrons, 31

Swinborne’s improved patented process for the preparation of
gelatine, 167

Table tops, paste for attaching cloth or leather to, 269

Tannery waste, yield of glue from, 18

Tannin as a test for the presence of gelatine, 165

—— effect of, on glue solution, 8

—— removal of, from leather waste, 39-41

Tendons, 1

Terne’s apparatus for the generation of sulphurous acid, 94

—— glue boiler, 51, 52

Terra-cotta articles, cement for, 232

Testing glue and gelatine, 205-217

Tin foil, paste for fastening paper on, 266, 270

Tin paste for attaching labels to, 268

Tires, cement for, 250

Tools for cutting the jelly into cakes, 59

Tortoise shell, cement for, 232

—— —— glue imitations of, 15

Toys indestructible mass for, 155

Tragacanth, 261

—— mucilage, 264

Transition stages of glue, 2, 3

Tub-size, manufacture of, 158, 159

Tungstic glue, 155

Turners, cement for, 229, 230

Twine netting, objections to, 66, 67

Under skin, 17

Uses of glue, 10-15

Vacuum pans, 101-103

Vasa lymphatica, 1

Vats, clarifying, 53

Veneers, gelatine, 15, 186-193

Venetian paste, 262

Walls, damp, marine glue for, 235

Wash basins, cement for, 225, 226

Washing drum, 22

Waste, green, liming of, 26, 27

—— liming of, 20

—— putrefaction of, 20, 21

Water-glass and water-glass cements, 240-242

—— —— constitution of, 240

Water-proof cement, 227

—— —— glue, 160

—— proofing fabrics, 161-163

—— —— wrapping paper, 160, 161

—— tanks, iron, cement for, 246

Weavers’ looms, worn-out hinges from, 30

Weidenbusch’s method of testing glue, 211-213

Whalebone, cement for, 232

Whale glue, 204

Whip leather, 30

White-lead, addition of, to glue, 149

Wood, cement for, 230, 239, 240

—— —— —— attaching metal letters to, 249

—— —— —— —— to metal, 251

Wooden vessels, insoluble cement for, 233

Wrapping paper, water-proof, 160, 161

Zinc plates, gelatinizing liquors upon, 58, 59

—— white cement, 226

—— addition of, to glue, 149

* * * * *

Transcriber's Notes

Obvious typographical errors have been silently corrected. Variations
in hyphenation have been standardised but all other spelling and
punctuation remains unchanged.

Italics are represented thus _italic_.

Within the chemical formulae subscripted numerals are shown thus _{2}_.

The following corrections have been made:

Line 4516 From
III. 3Ca(PO_{3})_{2} + 10C = 10CO + Ca_{3}(PO_{4})_{2} = P_{2}
to
III. 3Ca(PO_{3})_{2} + 10C = 10CO + Ca_{3}(PO_{4})_{2} + P_{4}

Line 4742 From
3Ca(PO_{3})_{2} + 5Ca_{2}_ = Ca_{3}(PO_{4})_{2} + 10CO + 4P.
to
3Ca(PO_{3})_{2} + 10C = Ca_{3}(PO_{4})_{2} + 10CO + 4P.

*** End of this LibraryBlog Digital Book "Glue, Gelatine, Animal Charcoal, Phosphorous, Cements, Pastes and Mucilages" ***

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