1880.] 071 Investigations at High Temperatures. 259 



nitrogen, as? wlion induction sparks arc passed through the mixed 

 gases, viz. : — 



C,H, + N, = 2HCN, 



and that the hydrogen is obtained from tlie decomposition of aqueous 

 vapour, and the combined hydrogen in the carbons. It is possible 

 that traces of alkaline salts in the carbon poles may favour the forma- 

 tion of hydrocyanic acid, but, as all attempts to purify the poles so as 

 to stop the reaction failed, I am inclined to believe it is a direct 

 synthesis. The acetylene reaction is one of the many remarkable 

 syntheses discovered by Professor Berthelot, of Paris. The presence 

 of sulphuretted hydrogen is doubtless due to the reduction of the 

 sulphates, invariably present in the ash of the carbon. 



The discovery of the formation of hydrocyanic acid in the electric 

 arc necessitated a more complete examination of the various reactions 

 taking place in the arc with poles of various kinds, and in presence of 

 different gaseous media. 



Various difficulties have impeded the satisfactory progress of the 

 investigation. During the course, however, of numerous experiments, 

 facts of interest have been recorded which are worthy of appearing as 

 preliminary results in a very extensive and difficult research. 



Formation of Cyanogen Compounds. 



The influence of impurities in the carbon on the production of 

 hydrocyanic acid had first to be ascertained. For this purpose, drilled 

 Siemens' carbons were placed in a porcelain tube, and treated for 

 several days at a white heat with a rapid stream of chlorine, until the 

 greater part of the silica, oxide of iron, alumina, &c., were volatilized 

 in the form of chlorides. Sometimes the carbons had a subsequent 

 treatment with hydrogen, or were directly treated with a current of 

 chlorine while the arc was in operation. 



Carbons treated in this way continued to yield hydrocyanic acid, 

 when a steady current of air was drawn through the positive pole 

 as formerly described, even when the same pole had several succes- 

 sive treatments with chlorine during the electric discharge. Natural 

 graphite poles gave the same result. 



As it was evident that the elimination of a large portion of the 

 impurities had little influence on the production of the hydrocyanic 

 acid, the only other explanation of its formation appeared to be the 

 presence of aqueous vapour, and organic impurities in the air, or a 

 direct formation of cyanogen from carbon and nitrogen through the 

 acetylene reaction formerly described. To obtain a pure and dry 

 atmosj^here in which such experiments could be carried out, the follow- 

 ing apparatus was employed : — 



A tin vessel. Fig. 2, about 2 feet high and 1 foot in diameter, had 

 an annular space, through which a constant stream of water was kept 

 flowing. This cylinder was placed upon a porcelain stand, having a 

 narrow groove filled with mercury, so as to make an air-tight joint. 



T 2 



