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Title: On the Existence of Active Oxygen - Thesis Presented for the Attainment of the Degree of Doctor - of Philosophy at the Johns Hopkins University
Author: Keiser, Edward H.
Language: English
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On the Existence of Active Oxygen.
Thesis
presented for the attainment of
the degree of Doctor of Philosophy
at the Johns Hopkins University.
by
Edward H. Keiser.
Baltimore,
1884
On the Existence of Active Oxygen.
That a gaseous element can exist in an allotropic condition was first
clearly shown by a careful study of the properties of ozone. Although
discovered by Schönbein in 1840, chemists were for a long time unable
to determine its true nature, and it was not until seven years later
that Marignac[1] succeeded in proving that it was oxygen in an
allotropic condition. Marignac’s work was confirmed by De la Rive, and
subsequently the elaborate researches of Andrews and Tait, and Soret,
as well as those of von Bato and Claus have established beyond all
question that ozone is an allotropic modification of oxygen, and that
its density is one and a half times that of ordinary oxygen.
The possibility of the existence of allotropic modifications of oxygen
having been thus established it is not surprising that attempts should
have been made to find other forms in which this element might occur.
As early as 1855 Houzeau[2] stated that when barium superoxide was
decomposed with concentrated sulphuric acid, at low temperatures, a
colorless gas was evolved which oxidized metals and ammonia. It had a
penetrating odor and possessed the power of bleaching litmus paper,
and liberated iodine from potassium iodide. By heating the gas to a
temperature of 75°C it was completely converted into ordinary oxygen.
He calls the gas _nascent_ oxygen and further states that it is
probable that whenever oxygen is set free from any of its compounds at
low temperatures it is in the nascent or _active_ state.
Clausius[3] at one time supposed that free atoms of oxygen might exist
in an uncombined state, and his hypothesis on the nature of ozone
was that this substance consisted of a mixture of molecules and free
atoms of oxygen. In a later paper[4], however, he abandoned this view
and regarded ozone as consisting of one or more atoms of oxygen feebly
united, (lose verbunden) with molecules of ordinary oxygen.
The idea that a third form of oxygen existed also obtained support from
the fact that certain organic substances when exposed to the light in
the presence of oxygen or air, acquire oxidizing properties. In 1850
Schönbein[5] stated that ether turpentine, and oil of lemons if allowed
to stand in diffused light in contact with the air acquires the
power of decomposing potassium iodide, and decolorizing indigo. In a
subsequent paper[6] he shows that methyl and ethyl alcohols, tartaric
and citric acids and even sulphuretted and arsenuretted hydrogen
in the presence of sun light can decolorize indigo. These studies
led Schönbein to publish a theory on the different modifications of
oxygen. In this paper[7] he states that besides ordinary oxygen there
are two other conditions in which it may exist one of these is ozone,
or positively electrified oxygen, the other _antozone_ or negatively
electrified oxygen. The union of ozone and antozone gives ordinary
oxygen. He also stated that antozone was formed by the action of light
on turpentine and air, and subsequently in 1862[8] he claimed that
antozone was identical with the gas obtained when barium superoxide
is treated with acids. Meissner[9] also supported the views of
Schönbein and claimed that antozone was formed in two ways:--1st, By
treating barium dioxide with concentrated sulphuric acid, 2nd, By the
electrification of oxygen; being produced simultaneously with the ozone.
These statements remained unquestioned for a number of years and are
found in the text books of the period, (for example Graham-Otto, and
Gorup-Besauez) but in 1870 Engler and Nasse[10] undertook a thorough
investigation to determine whether antozone existed. By treating
barium dioxide with strong sulphuric acid they find a gas to be given
off which is a mixture of ozone and hydrogen dioxide, and they also
show that the stronger the acid the greater the quantity of ozone
produced. Secondly, Meissner had stated that by the electrification of
oxygen ozone and antozone were formed. The evidence of the existence
of antozone being this; when the ozonized oxygen was passed through a
solution of potassium iodide to destroy the ozone, the residual gas
gave white fumes when brought into contact with water, and after a time
hydrogen dioxide could be detected in the water. Schönbein and Meissner
held that the ozone having been destroyed by the potassium iodide
the antozone passed on and oxidized the water to hydrogen dioxide.
Now Engler and Nasse show that when ozone is decomposed by easily
oxidisable substances in the presence of water hydrogen dioxide also is
formed, and it was the vapor of this compound which had been regarded
as antozone. It is known that ozone cannot oxidize water, but that it
is to a slight extent oxidized when other oxidisable substances are
present is not surprising, as other phenomena of a similar kind are
known. Thus when nitric acid acts on an alloy of silver with gold or
platinum, containing a certain proportion of silver, some of the gold
or platinum are dissolved although by themselves they are insoluble.
When ammonia burns some of the nitrogen as well as the hydrogen is
oxidized. Engler and Nasse therefore conclude that there is no basis
for the assumption of a third form of oxygen having the properties
attributed to antozone.
Berthelot[11] and Houzeau[12] conclude from their investigations that
the oxidizing properties which turpentine and other organic compounds
acquire under certain conditions is due to the formation of unstable
oxygenated compounds which readily decompose giving up oxygen.
Fudakowski[13] has described experiments showing that benzene can become
active, i.e. acquire oxidizing properties, but states that he is unable
to explain the phenomenon. Loew[14], however, believes active turpentine
to contain atomic oxygen or antozone in solution.
After Engler and Nasse had demonstrated the nonexistence of antozone
all discussion on the subject ceased for a number of years, and it
was not until 1878 that Hoppe-Seyler[15] again opened the question. In
studying the processes of putrefaction he observed that free hydrogen
is given off in those cases in which oxygen is not present, and that
whenever oxygen has access to decaying liquids, not only is all the
hydrogen oxidized but energetic oxidation processes are observed as
well. The simplest explanation of this seemed to be that the nascent
hydrogen has the power of splitting up the oxygen molecule, uniting
with one atom and setting the other free, and these free atoms he
imagined brought about the strong oxidations which take place in
decaying bodies.
To test this hypothesis he made experiments with palladium hydrogen.
Graham has described the energetic reducing power of this compound but
that it can also cause oxidations Hoppe-Seyler showed by bringing some
strips of palladium charged with hydrogen into a solution of indigo
in the presence of air. The solution soon became yellow and after a
time the indigo was completely destroyed. If palladium hydrogen be
brought into a neutral solution of potassium iodide and starch, the
liquid becomes blue in a few minutes, after which the starch is slowly
destroyed. In a similar way benzene was oxidized to phenol. “These
experiments and others of a similar nature,” he asserts, “admit of no
explanation other than that the active hydrogen renders the oxygen
active, and since the former unites with oxygen we cannot well conceive
of the process without supposing that the hydrogen in uniting with one
atom of the molecule O_{2} sets the remaining atom free, thus making it
active.” “Just as the hydrogen atom cannot exist in a free state so the
active oxygen, if no oxidizable material is present, unites with water
to form hydrogen dioxide, or with inactive oxygen to form ozone.”
This theory has been taken up and developed by Baumann, who in 1881
published a paper[16] entitled “Contribution to the knowledge of Active
Oxygen.” The paper begins with the statement that besides ordinary
inactive oxygen and ozone there is a third modification known as
active or nascent oxygen. He states that this active oxygen cannot
be isolated, and its formation can only be recognized by its action
on other bodies. “Active oxygen (O) is the most powerful oxidizing
substance known and can unite with inactive oxygen (O_{2}) to form
ozone (O_{3}). The production of ozone is always preceded by the
formation of active oxygen,” but he states “active oxygen can be formed
under conditions when no ozone can be formed, this is the case when
easily oxidized substances are in contact with the active oxygen in
such a way that the latter is completely consumed in oxidizing those
substances.” “Thus, for instance, ozone is formed when oxygen is
rendered active by the slow combustion of moist phosphorus in air,
but no ozone is formed if the atmosphere surrounding the phosphorus
contains the vapor of alcohol, ether and similar substances.” The
fallacy of this reasoning becomes apparent on referring to the work of
Müller[17] on the luminosity of phosphorus who shows that substances
which prevent the luminosity also prevent its oxidation and if the
phosphorus is not oxidized we have no reason for assuming the formation
of active oxygen.
He then compares active oxygen with the antozone of Schönbein and says
that several of the properties of antozone can be ascribed to active
oxygen above all that property of antozone of oxidizing water to
hydrogen dioxide. The only difference between the two being that active
oxygen has but a momentary existence while antozone was supposed to be
capable of isolation.
Baumann then describes results obtained by himself which enable us to
clearly distinguish between active oxygen and ozone. Starting from
the observation of Remsen[18] and Southworth that carbon monoxide, at
ordinary temperatures, is not oxidized by ozone, he suspected that
active oxygen would readily effect its oxidation. Palladium hydrogen
was therefore sealed up in a capacious glass tube with a few cubic
centimeters of clear lime water and a mixture of carbon monoxide and
oxygen free from carbon dioxide. At first the lime water remained
clear, but after several hours a cloudiness in the lime water became
visible and after several days a precipitate of calcium carbonate
settled to the bottom of the tube. He then repeated the experiment in a
modified form. From a gasometer, containing a mixture of three volumes
of oxygen and one of carbon monoxide free from carbon dioxide a slow
current of gas was passed, first into a wash bottle containing a clear
solution of baryta water, then into a tube containing palladium
hydrogen. Then the gases were again passed through a wash bottle
containing baryta water. After the current had been passing for four
hours, the first baryta water was still perfectly clear, but the
second showed a distinct cloudiness of barium carbonate, which slowly
increased in the course of twelve hours. The baryta water in the first
wash bottle remained clear even to the end of the experiment.
The different behavior of ozone and active oxygen was then shown by the
following experiment:--“A slow current of air free from carbon dioxide
was passed into a flask containing moist phosphorus, from there into a
second flask where the ozonized air came in contact with a somewhat
slower current, consisting of a mixture of three volumes of oxygen to
one of carbon monoxide, carefully purified from carbon dioxide. From
the second flask the gases were passed through a clear solution of
baryta water.” “After all carbon dioxide had been removed from the
apparatus the baryta water remained perfectly clear (völlig klar) after
the gases had passed through for six hours.” “But, on the other hand,
if the mixture of carbon monoxide and oxygen was passed into the first
flask, containing the moist phosphorus and in which according to our
theory active oxygen must occur, then the result is quite different,
the baryta water becomes cloudy in a short time and in the course
of an hour there is formed an _abundant precipitate_ (‘reichlicher
Niederschlag’) of barium carbonate.”
From these results he concludes that active oxygen may be detected
by its power of oxidizing carbon monoxide, and states that this fact
enables us to decide whether in oxidations effected by ozone there
occur free atoms of oxygen.
Closely related to these experiments of Baumann are those of Professor
Remsen[19] on the transformation of ozone into oxygen by heat. Now if
atoms of oxygen can exist in the free state, it is difficult to see why
transformation some of the oxygen atoms should not be in the free
condition, and the statements of Baumann being true, if carbon
monoxide is also present this should be oxidized. To test the question
a gasometer was filled with carbon monoxide made from potassium
ferrocyanide and sulphuric acid. Before entering the gasometer the
gas was purified by passing through four wash bottles containing
concentrated sodium hydroxide. Another gasometer was filled with pure
oxygen. The ozone was produced by the silent electric discharge in a
Wright’s tube connected with a Stoltz electrical machine. In detail the
experiments were conducted as follows:--
A slow current of oxygen from the gasometer was passed through three
woulfe bottles containing a concentrated solution of caustic soda and
then into the ozonizer, the ozonized oxygen was then passed into a U
tube, rubber joints between the ozonizer and U tube were found to be
rapidly perforated and were replaced by a device of this kind:--
[Illustration]
A, the tube from the ozonizer was introduced several inches into B,
the tube leading to the U tube, and the joint C was closed by a cement
composed of beeswax and paraffin. The carbon monoxide was passed
through wash bottles containing caustic soda and finally through baryta
water. The two gases were then brought together in a U tube placed
in an air bath. After leaving the U tube the gases passed through
perfectly clear lime water. Under these conditions the current of the
gases was continued for an hour, and no precipitate was formed in the
lime water.
“Separate experiments were made for the purpose of determining how
readily the ozone was destroyed, and it was found that, even when the
thermometer in the U tube indicated a temperature considerably below
that stated as the decomposition temperature of ozone, and when highly
ozonized oxygen was certainly entering the U tube, no ozone passed out,
whether carbon monoxide was present or not in the tube at the same
time.” The experiment as thus described was repeated several times,
but always with the same result. “One modification of the experiment
should also be mentioned in this connection. In order to get as good
ozone as possible the ionizer was filled with oxygen and the current
of gas stopper, the silent discharge was allowed to continue for a
few minutes, then the gas was slowly passed into the heated U tube
containing carbon monoxide. This interrupted current of oxygen was
continued for about an hour but no oxidation of carbon monoxide to
dioxide could be detected.” The conclusion that must necessarily be
drawn from the result is that if carbon monoxide is a test for active
oxygen, then when ozone is decomposed by heat there is no nascent or
active oxygen formed.
The negative result obtained in the preceding investigation, naturally
called in question the accuracy of Baumann’s statements in regard to
the formation of active oxygen by the slow oxidation of phosphorus,
and of palladium hydrogen in the presence of oxygen and water. The two
experiments upon which he had based his conclusion have been described
on pages 16 and 18. The first of these was that palladium hydrogen
in the presence of oxygen and water effected the oxidation of carbon
monoxide, the second, that when carbon monoxide was brought in contact
with moist phosphorus and air oxidation was observed.
In regard to the first of these experiments Traube[20] has carefully
investigated what takes place when palladium hydrogen is allowed to
remain in contact with water and oxygen. Hoppe-Seyler had noticed
that under these conditions small quantities of hydrogen dioxide were
formed, but he attributed this to the union of the active oxygen
with the water. Traube, on the other hand, finds that in the formation
of hydrogen dioxide under these circumstances there is nothing formed
which has oxidizing properties, not even indigo sulphuric acid is
oxidized. He shows by direct experiments that nascent hydrogen can not
by its action on oxygen produce active oxygen or ozone. He finds the
action of palladium hydrogen to be analogous to that of zinc and other
metals, which when allowed to oxidize slowly in contact with air and
water give rise to the formation of hydrogen dioxide. The process is to
be regarded rather as a reduction of molecules of oxygen than as an
oxidation of water. Traube represents the action by the following
equations:--
+--------------------+--------+ OH
| OH|H O| /
| Zn | | = Zn + H_{2}O_{2}
| Zn + OH|H + O| \
+--------------------+--------+ OH
+--------------------+----------+
| Pd_{2}H OH|H |
| + | + O_{2} | = 4 Pd + 2 H_{2}O + H_{2}O_{2}
| Pd_{2}H OH|H |
+--------------------+----------+
He proves by direct experiments that no active oxygen is formed
during this process, and points out that the oxidations observed by
Hoppe-Seyler and Baumann must have been brought about by the hydrogen
dioxide. But this would not account for the oxidation of carbon
monoxide, for it has been previously shown by Remsen[21] that hydrogen
dioxide cannot oxidize carbon monoxide, not even when it is heated
to its point of decomposition. Traube[22] therefore repeats Baumann’s
experiment, he finds that palladium hydrogen in the presence of water
and oxygen does oxidize carbon monoxide; but as he had shown that
no active oxygen was formed during the process, and as the hydrogen
dioxide could not cause the oxidation, he concluded that the palladium
itself must play an important role in the reaction. By further
experiments he soon became convinced that there are two stages in the
process. 1st the palladium hydrogen acting on water and oxygen forms
hydrogen dioxide, 2nd the hydrogen dioxide in the presence of palladium
oxidizes the carbon monoxide. Traube[23] introduced into a glass flask
containing carbon monoxide a dilute solution of hydrogen dioxide and
a small piece of palladium foil, previously ignited, the action was
allowed to continue for 22 hours after which the CO was replaced by
air free from carbon dioxide. After leaving the flask the gas passed
through a solution of barium hydroxide; an abundant precipitate was
formed, showing that in this case the quantity of carbon dioxide formed
was greater than in the first experiment, in which he used palladium
hydrogen, water, oxygen and carbon monoxide.
Traube’s conclusion is as follows:--
“The carbon dioxide obtained in Baumann’s experiments is not formed
during the oxidation of the hydrogen of the palladium hydrogen, (there
being formed by this action merely hydrogen dioxide and palladium free
from hydrogen) but by the combined action of these last two substances
on carbon monoxide.” “Therefore, the proof is given that the act of
slow combustion (Autoxidation) has not in itself the power of making
oxygen active.”
The conclusion reached by Traube was tested by Professor Remsen and
myself in the following way: A current of carbon monoxide was passed
through several wash bottles containing solutions of caustic soda,
then through a wash bottle containing clear baryta water, then into a
flask containing a solution of hydrogen dioxide, containing a slight
excess of hydrochloric acid. The flask also contained a small piece
of palladium foil free from hydrogen. After leaving the flask the gas
passed through a solution of baryta water, which was protected from the
air by a U tube containing solid KOH. It was only necessary to pass the
carbon monoxide through for a very short time to obtain an abundant
precipitate of barium carbonate. We also noticed that under these
conditions the palladium foil was dissolved.
From these experiments it is clear that the oxidation phenomena which
Hoppe-Seyler and Baumann attributed to active oxygen are really due to
the combined action of palladium and hydrogen dioxide, and to suppose
that atomic oxygen exists in the free state at any time during the
process is entirely gratuitous.
It remained to test the second of Baumann’s statements; namely that
carbon monoxide in the presence of moist phosphorus and air is oxidized
to carbon dioxide by the active oxygen formed by the slow combustion
of the phosphorus. Leeds[24] also has on record an experiment on this
subject, in which he claims that under these conditions oxidation takes
place. In taking up the subject, therefore, Prof. Remsen[25] and myself
have taken the greatest care to avoid all sources of error. We tried
the effects of passing air alone freed from carbon dioxide over moist
phosphorus and then into clear baryta water, Baumann[26] states that
this can be done, and the baryta water remains perfectly clear, even if
the current of air is passed for six hours. We obtained a precipitate
immediately. Thinking this might be caused by the white vapors which
are formed during the process, we passed the gas after its exit from
the vessel containing the phosphorus through a layer of previously
ignited asbestos. The layer of asbestos was between two and three feet
in length and the air after having traversed it no longer contained
any white fumes. From the asbestos tube the air passed into a solution
of clear baryta water. A precipitate was formed at once and increased
in quantity the longer the current continued. “It was tested for
phosphoric acid and phosphorus in general but not a trace could
be detected. The current of air over the phosphorus was continued
for several days in order to obtain enough of the precipitate for
examination and analysis. It proved to be nothing but barium carbonate.”
“The carbon dioxide must have come from one of two sources, either
from some carbonaceous substance contained in our phosphorus, or as
the result of the action of ozone on the cork stoppers used to make
connections. The use of rubber was avoided as far as possible, and
every precaution was taken as in the earlier experiments on the carbon
monoxide and ozone. It did not appear improbable therefore that the
difficulty arose from the use of impure phosphorus. Phosphorus was,
therefore, obtained from as many different sources as possible, and
with each of these the above described experiment was repeated, using
the same apparatus. In every case the precipitate of barium carbonate
was obtained and as far as could be estimated in about the same
quantity. Attempts were then made to purify the phosphorus. One
specimen was placed in hot water under the receiver of an air pump and
the air exhausted, for the purpose of recovering any gases which might
be contained in the phosphorus. Other specimens were distilled in an
atmosphere of pure hydrogen and the vapor condensed in cold water. No
matter what process of purification had been adopted the phosphorus
acted in the same way afterwards as before.”
“We then constructed an apparatus in which the gases could at no point
come in contact with cork stoppers or rubber joints. This consisted of
a flask of from three to four litres capacity, provided with a doubly
perforated cork stopper. Through this there passed one glass tube
reaching to the bottom of the flask, and another reaching only half
way. Outside the flask the shorter tube was connected with the wash
bottles used to purify the air from carbon dioxide, while the longer
tube was bent twice at right angles, and passed through the stopper of
a U tube about 8 in. high. In the flask there were placed two or three
sticks of phosphorus, each three or four inches long, and enough
distilled water to somewhat more than fill the neck when the flask was
inverted. The U tubes were filled with moistened asbestos which had
been previously ignited. There was then added some mercury, so that
when the tubes were inverted in which position the entire apparatus
was placed when in use the mercury covered the corks with a layer from
three quarters to an inch in thickness.
The last U tube was connected with the vessel containing the baryta
water by means of a mercury joint. The baryta water was protected from
the action of the air by placing before it a small U tube containing
solid potassium hydroxide, this was in connection with an aspirator.
Before connecting the bulbs containing the baryta water, air free from
carbon dioxide was drawn through the apparatus. On now connecting the
baryta water bulbs no precipitate was formed. About one third of the
air in the flask was replaced by pure carbon monoxide, the mixture was
allowed to remain several hours in contact with the moist phosphorus
and then drawn through the baryta water bulbs. No precipitate was
formed. This experiment was frequently repeated with the same result.”
“In some cases the air & carbon monoxide were drawn together slowly for
several hours over the phosphorus, but this made no difference in the
result.”
Having found, therefore, no evidence of the oxidation of carbon
monoxide, we have no right to assume that when phosphorus oxidizes
slowly in the presence of water and air that there is formed an active
condition of oxygen distinct from ozone.
To this paper both Baumann[27] and Leeds[28] replied. The former
recognizing the necessity of avoiding all connections of rubber or
organic matter, describes a new form of apparatus, in which the joints
are all made of ground glass. With this new apparatus he finds that
he can pass air over phosphorus at the rate of from two to three
bubbles per second, then through 10 cubic centimetres of water, and
finally into baryta water, and claims that only a slight turbidity of
phosphate and phosphite of barium is formed in the course of several
days! This statement to us is incomprehensible and as will be evident
from what follow, unless Baumann had phosphorus absolutely free from
carbon (of which he makes no mention and which as far as we know it is
impossible to obtain) he has described an impossibility. On introducing
100 cubic centimetres of carbon monoxide into the air every two hours
he soon obtained a distinct cloudiness which constantly increased,
until in 10 hours the inlet tube in the baryta water became stopped up
and the experiment was discontinued. He then determined the percentage
of oxidation; his results are as follows--
700 cubic centimetres of carbon monoxide mixed with enough air to
require 15 hours to pass through the apparatus gave 366 milligrams
CO_{2} or 2.6% of oxidation. In another experiment a mixture consisting
of thirty litre of air and 2.45 litres of carbon monoxide, requiring 12
hours in passing the phosphorus, gave 466 milligrams of CO_{2}, or 1.3%
of the original quantity of monoxide was oxidized.
Baumann, in the arrangement of his apparatus, has taken no precautions
to prevent the air from coming in contact with organic connections
before it is introduced into the flask containing the phosphorus. Now
Karsten[29] has shown that air alone when it comes in contact with the
organic matter of corks and connectors forms carbon dioxide; it is,
therefore, highly probable that in the course of from 12 to 15 hours a
portion of his precipitate was due to this cause. The reminder came, as
will appear presently, from carbon contained in the phosphorus.
Leeds conducted his experiment as follows:--A ten litre flask provided
with a glass stopper, was filled with a mixture of equal parts of
carbon monoxide and air, and allowed to stand in contact with moist
phosphorus for six days. The glass stopper was then removed and
replaced by a cork; and the mouth of the vessel being placed under
mercury, the gases were displaced and passed through baryta water. A
precipitate containing 15.5 mg of carbon dioxide was obtained. It is
evident that in the course of six days, in a tightly closed vessel, the
oxygen of the air must have been completely used up so that the mixed
gases were necessarily under diminished pressure. Then in taking
out the glass stopper for the purpose of introducing the cork, no
precautions were taken to prevent the access of ordinary air, and a
considerable volume of the air of the laboratory must have entered;
enough, certainly, to account for some of the precipitate he obtained.
The rest of the carbon dioxide must have come as in Baumann’s
experiment from the oxidation of carbon contained in the phosphorus.
That ordinary commercial sticks of phosphorus contain carbon was shown
by us in the following way[30]:--Air was passed from a gasometer into a
hard glass tube containing copper oxide heated to redness, represented
by K in the drawing. Then through a series of wash bottles A, B, C, so
constructed that the connecting tubes were fitted into each other by
means of ground glass joints. A and B contained a concentrated solution
of caustic soda, C a solution of baryta water. The air then passed into
an ordinary bell jar, having a capacity of about a litre and a quarter.
This was held in position on mercury contained in a crystallizing dish.
The inlet tube was bent downward into a small dish containing the
phosphorus, represented by H in the figure. The gas after leaving the
bell jar passed through two wash bottles D and E, similar to A, B, C. D
contained 30-40 c.c. of ordinary distilled water. E contained a clear
solution of baryta water, and was connected with a tube containing
solid caustic potash to protect it from the air. The outlet tube from
the wash bottle C is bent so as to pass beneath the edge of the bell
jar, then up into the closed space above the mercury, and then down
towards the phosphorus. A long funnel tube J served to introduce or
remove water from the dish containing the phosphorus. The air therefore
after having entered the tube K came at no point in contact with
organic matter, and yet we found that after all ordinary air had been
displaced by purified air, and clear baryta water introduced into
the wash bottle E, a precipitate was found. Ten litres of air were
sufficient to cause a distinct turbidity, while 20 to 30 gave a
precipitate. As there is no possible source of error it follows
that the carbon dioxide must have come from the oxidation of carbon
contained in the phosphorus.
[Illustration]
That carbon should be present in phosphorus is not surprising
considering its method of manufacture. Whether the carbon existing in
the phosphorus is in chemical combination or not we are unable to say.
The specimens of phosphorus used by us were perfectly homogenous. There
was no evidence of the presence of particles in them, and the solution
in carbon bisulphide was perfectly clear, and on standing nothing
whatever was deposited. Even distilled phosphorus acted in the same
way, showing that this also contained carbon.
A simple way to show the presence of carbon in any sample of phosphorus
is to burn a small piece of the latter in a small porcelain dish,
floating in water under a bell jar fitted with a glass stop cock. After
the combustion is over the vessel is allowed to stand some time until
the white fumes have entirely disappeared. The gas is then passed
through water and finally into baryta water where a precipitate is
invariably formed. The air in the bell jar must of course be free from
carbon dioxide. As the bell jar is only lifted far enough to permit the
introduction of the dish with the phosphorus, and this operation is
performed instantaneously, the amount of carbon dioxide thus introduced
can only be infinitesimal.
We now made some experiments with the object of determining whether
changes in the amount of phosphorus exposed in the bell jar F of our
ozonizing apparatus had any effect upon the amount of barium carbonate
formed in the wash bottle E. We found that the amount of precipitate is
plainly influenced by the rate of passage of the gases, the temperature
and the amount of phosphorus exposed, but that if the temperature is
between 20 and 25°C, the rate of passage of the air about two or three
bubbles per second, and the amount of phosphorus exposed from 20 to 30
grams a slight precipitate is always formed by 10 litres of air, and
that 25 to 30 litres give a decided precipitate.
Having therefore demonstrated the presence of carbon in all the
specimens of phosphorus at our disposal, and knowing that purified air
alone when passed over phosphorus would give a precipitate when
passed into baryta water, we next determined whether if carbon
monoxide being present in the air passing over the phosphorus,
and all other conditions the same, the amount of precipitate is
increased. For this purpose parallel experiments under as nearly
the same conditions as possible were made one with air alone, the
other with air and carbon monoxide. In the first experiment about
25 litres of air were passed through the apparatus, the conditions
being carefully noted. The wash bottle containing the precipitate
was removed at the end of the operation, instantly stoppered and set
aside for comparison.
The water was then removed from the wash bottle D and replaced by fresh
distilled water, a new bottle attached in the place of E and after
passing about a litre of pure air through the apparatus, the necessary
quantity of baryta water filtered rapidly through a plaited filter into
the wash bottle.
Now the experiment was repeated, with the difference that during the
passage of twenty-five litres of air, a very slow current of carefully
purified carbon monoxide (made from pure sulphuric and formic acids)
was passed through three wash bottles, like those used for the air, and
containing the same substances, and then into the bell jar containing
phosphorus and air. The rate of the current was so regulated that
during the time of the experiment, which varied in different cases
from three to eight hours, three litres of carbon monoxide were used.
The same slow formation of a precipitate was noticed when the carbon
monoxide was used as in the case of air alone. At the end of the
operation we were unable to distinguish any difference between the
amounts of the small precipitates formed. They did not appear to be
as great as that found by Baumann, they were too small to permit of
accurate filtering and weighing, if we consider the nature of the
liquid in which they were present.
The only conclusion which we can draw is, as is stated in the first
paper on this subject, that carbon monoxide is not oxidized by air in
the presence of moist phosphorus.
That in our first experiments we did not obtain evidence of the
presence of carbonic of phosphorus is due to the fact that we worked
with small volumes of the gases. In those cases in which relatively
large volumes were used the slight cloudiness produced was disregarded
as the same result was obtained with air alone.
Having, therefore, been unable to obtain any evidence of the
oxidation of carbon monoxide when phosphorus undergoes slow
combustion in the presence of air and water, the second and last
of Baumann’s arguments for the existence of active oxygen becomes
untenable. Whether oxygen ever does occur in the so called active
condition still remains to be shown.
That the nascent state of an element should be due to the momentary
existence of free atoms is entirely hypothetical. Tommasi[31] has
shown that the properties of nascent hydrogen vary according to the
method by which it is formed. He regards nascent hydrogen as ordinary
molecular hydrogen plus varying quantities of heat, and he shows that
as the heat of the reaction varies so the activity of the hydrogen
varies. The same is undoubtedly true of oxygen, for it is known that
oxygen evolved by some reactions is more powerful than by others.
That we shall ever be able to show that this heat in some cases is
sufficient to dissociate the molecules of oxygen seems improbable.
Baumann[32] has recently published another paper, but has failed to
contribute either new facts or ideas on the subject.
Estimation of Carbon in Phosphorus.
Having found carbon present in all varieties that we examined,
we naturally attempted its quantitative determination. Our first
experiments did not prove successful. Chromic acid was tried,
but this gave unsatisfactory results for the reason that it was
impossible to control the action and at the same time secure complete
oxidation of the phosphorus. With concentrated solutions the action
is liable to become violent unless the temperature is kept low.
We also arranged an apparatus similar to that used in making
phosphorus pentoxide on the small scale. The combustion took place
in a bell jar filled with pure air, and after being thoroughly
washed the gases were passed through baryta water. The operation was
imperfect owing to the formation of red phosphorus, and to incomplete
oxidation.
Finally we succeeded in obtaining satisfactory results by using
nitric acid of 1.2 sp gr. The phosphorus was oxidized in a retort
of 500 c.c. capacity. The retort was inclined so that any liquid
condensing in the neck would run back. A glass tube fitted to the
neck of the retort by means of gypsum served to convey the evolved
gases into a wash bottle containing pure water. The latter was
connected with a combustion tube containing in one end a layer of
metallic copper about six inches in length, this served to decompose
the oxides of nitrogen. The remainder of the tube was filled with
copper oxide, which served to oxidize any carbon compound, which
might be formed by the oxidation of the phosphorus, to carbon
dioxide. After leaving the combustion tube the gases passed, first
through a wash bottle containing water, then into one containing
clear barium hydroxide, which was protected from the action of the
air. All joints which were not of ground glass were made by means
of gypsum. The operation was conducted as follows:--After 200 to
300 cubic centimetres of nitric acid (sp gr 1.2) and the weighted
quantity of phosphorus had been introduced into the retort, a slow
current of air free from carbon dioxide was drawn through the
apparatus. The tubulus of the retort was then closed by means of a
glass stopper, the combustion tube containing the metallic copper and
copper oxide heated to a red heat, and a solution of baryta water
rapidly filtered into the last wash bottle. The retort was then
heated gently, after a time a regular evolution of gas takes place,
and a precipitate gradually forms in the baryta water. At the end
of the operation, air free from carbon dioxide is again drawn
through the apparatus to remove all of the oxidation products.
The precipitate is allowed to settle, the clear liquid is rapidly
decanted through a filter. The precipitate is then washed, and
quickly brought upon the filter paper. The filtering is done by means
of a pump and is very rapid. The precipitate is then dissolved in
dilute hydrochloric acid and the solution heated to boiling and the
barium precipitated by sulphuric acid in the usual way. From the
weight of barium sulphate obtained, the quantity of carbon in the
phosphorus is readily calculated.
In some instances the experiment was varied by using a large quantity
of phosphorus and allowing the action to continue for two or three
hours, then weighing the phosphorus which remained unacted upon. In
two instances the carbon dioxide was weighed directly by replacing
the wash bottle containing the baryta water by weighed potash bulbs.
The following are the results obtained
I. 6.2272 grams Phosphorus gave .0300 gr
BaSO_{4} = .0057 grm CO_{2} = .0016 gr C = _.026%C._
II. 7.9545 grm Phosphorus gave .0324 gr CO_{2}
= .0088 gr Carbon = _.111% Carbon_
III. 8.8041 grm Phosphorus gave .0134 gr CO_{2}
= .00365 gr Carbon = _.042% Carbon_
IV. 9.0650 grm Phosphorus gave .0540 BaSO_{4}
= .0101 grm CO_{2} = .00278 gr C = _.031% C._
V. 16.4633 grm Phosphorus gave .1303 gr
BaSO_{4} = .0246 gr CO_{2} = .0067 C = _.041% C._
VI. 11 grams Phosphorus gave .0929 grams
BaSO_{4} = .0175 gr CO_{2} = .00478 C = _.043% C._
Footnotes:
[1] Annales de Chim. et de Phys. _14_-252
[2] Poggendorf. Ann. _95_-484 Journ. f. prakt. Chemie. _65_-499
[3] Pogg. Ann. _103_-644
[4] Pogg. Ann. _120_-250
[5] Journ. f. prakt Chem. _52_-135
[6] Journ f. prakt. Chem. _53_-65
[7] Journ f. prakt. Chem. _77_-129
[8] Journ f. prakt. Chemie _86_-65
[9] Untersuchungen über Sauerstoff. Hanover 1863
[10] Liebig’s Annalen _154_-215.
[11] Annales de Chim. et de Physiologie _3_-58
[12] Compt. Rendus _50_-829
[13] Berichte der Deutschen Chem. Gesellschft. _6_-108
[14] Zeitschrift f. Chemie (1870) _6_-611
[15] Zeitschrift f. Physiol. Chemie _2_-22
[16] Zeitschrft. Physiol Chem. _5_--244
[17] Berichte der Deutsch. Chem. Gesell. _3_-84
[18] Berichte der Deutsch. Chem. Gesell. _8_-1415
[19] American Chemical Journal _4_-50
[20] Berichte d. Deutsch. Chem. Gesell. _15_-2421
[21] Berichte der Deutsch. Chem. Gesell. _15_-222
American Chem. Journ. _4_-53
[22] Berichte der Deutsch. Chem. Gesell. _16_-123
[23] Berichte der Deutsch. Chem. Gesell. _16_-126
[24] Journal Am. Chem. Soc. _1_-232
[25] American Chem. Journal _4_-454
[26] Zeitsch. f. phys. Chem. _5_-250
[27] Berichte der Deutsch. Chem. Gesell. _16_-2146
[28] Chemical News _48_-25
[29] Poggendorff’s Annalen _115_-348.
[30] American Chemical Journal _5_-426.
[31] Bulletin Soc. Chim. _38_-148
[32] Berichte d. Deutsch. Chem. Gesell. _7_-283
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