Part 2

“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.

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