76 Mr Johnston ofi a solid form of Cyanogen. 



or olive black colour, but where thinly spread over the inner 

 surface of the tube, it is by transmitted light of a brownish 

 red. It is easily rubbed to powder, and soils the fingers. In 

 the flame of a lamp it burns very slowly and without noise or 

 flame. Heated to redness in a glass capsule it gives off no 

 fumes, and is dissipated with extreme slowness, leaving no ap- 

 preciable residuum ; — at a higher heat in a silver or platinum 

 crucible, it melts and disappears more rapidly. It will be seen 

 in the sequel of this paper, what changes take place in the 

 chemical constitution of this substance when thus heated in 

 contact with atmospheric air. 



In the state of fine powder this substance is insoluble in al- 

 cohol, ammonia, or nitric acid. It dissolves in hot and concen- 

 trated sulphuric and muriatic acids, giving with the latter a 

 light yellowish brown solution. After evaporation to dryness, 

 the residuum from both acids is insoluble in water, that from 

 the muriatic acid is of a reddish, from the sulphuric of a gray- 

 ish black colour. It is partly taken up also by caustic potash, 

 probably by its agency in effecting decomposition. Triturat- 

 ed in a mortar with chlorate of potash, it detonates by heat, 

 but not by percussion. 



This residuum has hitherto been regarded as a variety of 

 carbon, and has, therefore, obtained little attention. It has 

 been thought, that during the decomposition of the cyanide, a 

 portion of the cyanogen also was decomposed, the carbon re- 

 maining in the tube, and the azote passing over with the cy- 

 anogen. But cyanogen is often obtained, almost, if not per- 

 fectly pure, while still a considerable portion of the carbonace- 

 ous matter is found in the tube. If such be the case, it is ob- 

 vious that this substance must be something more than mere 

 carbon. Accordingly, in analyzing it by means of chlorate of 

 potash, I found it to be identical in constitution with gaseous 

 cyanogen. The results of analysis uniformly give carbonic 

 acid and azote in the proportion almost exactly of two volumes 

 of the former to one of the latter. The mean of seven expe- 

 riments which I here subjoin gives 



Carbonic acid, - - 2.32 inches. 



Azote, - - - 1.173 



where the proportion is clearly as above stated. While in 



