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 CO2 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 CO2, 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.