ANILINE AS ABSORBENT OF CYANOGEN 249 



acid became apparent. It was expelled from the aniline by 

 the carbon dioxide, and could now be recognized both by its 

 odor and by the Prussian blue reaction. At the same time a 

 considerable quantity of carbon dioxide is absorbed by the ani- 

 line and must be held in solution, as chemical union is impos- 

 sible under the circumstances. As the same is said to be the 

 case with carbon monoxide, and these two gases are those 

 which generally accompany cyanogen, I fail to see how aniline 

 can be generally useful in determining the amount of cyano- 

 gen in a mixture, apart from the fact that hydrogen cyanide 

 is produced in the reaction, and is itself very loosely attracted 

 by aniline. 



The experiments by which I satisfied myself of this were 

 made last April, in the laboratory of the Physical Association 

 of Frankfort-on-Main, to the director of which, Dr. B. Lep- 

 sius, I am very much indebted. The details of a few of the 

 most important tests are given below. 



I. 32*88 cc. of cyanogen gas (under standard conditions) 

 were absorbed immediately by 12*5 cc. aniline; after twenty- 

 five hours no trace of gas had been evolved. 



II. A mixture of cyanogen and dry air was introduced into 

 a T-shaped eudiometer, provided with stopcocks and filled 

 with mercury. Aniline was first added and allowed to absorb 

 the cyanogen, and dry carbon dioxide was then passed in; 

 when no further change took place, the unabsorbed gas was 

 transferred to a test-tube over mercury, and brought in con- 

 tact with a few drops of sodic hydrate; the alkaline solution 

 gave an appreciable test for hydrocyanic acid with ferrous 

 and ferric salts. In the table [on the following page] the 

 measurements and the results are given: 



