^g MR JOHNSTON ON PARACYANOGEN. 



water, and hence the difficulty of obtaining a neutral solution. But this is a 

 matter for future investigation. 



Rendered neutral by an acid, the solutions of the alkaline paracyanates are 

 precipitated by the salts of oxide of silver and of protoxide of mercury ; an excess 

 of acid decomposes them, and throws down the paracyanic acid. 



In my paper pubhshed in 1829, I suggested that the nitrogen kno^vn to exist 

 in certain vai-ieties of coal, might be present in them in the state of paracyanogen. 

 I find that fine caking coal fi-om Killingworth colliery near NcAvcastle, which con- 

 tains nitrogen equal to about one-ninth of the weight of carbon, and leaves only 

 0.95 per cent, of ash, dissolves completely in hot nitric acid, with copious evolu- 

 tion of red fumes, giving a dark broAvn solution. Water throws down a reddish- 

 brown powder, and the yellow supernatant liquid gives a reddish-brown precipi- 

 tate with nitrate of mercury. The substance thrown doMTi by water when 

 burned vsdth bichromate of potash, gave a mixture of gases containing about eight 

 per cent, of nitrogen. The subject, therefore, is worthy of future investigation. 



In concluding this paper, I would draw the attention of chemists to the very 

 remarkable discordance between the properties of cyanogen and paracyanogen 

 aud their several compounds; a discordance certainly more striking than any 

 other with which we are yet acquainted among isomeric bodies. I have already 

 adverted to the analogy which this black substance seems to exhibit in some of 

 its chemical relations to the hydrocarbons. It also agrees with them in the multi- 

 ple ratio of the elementary atoms existing in its equivalent as compared with that 

 of cyanogen ; and in the less stability and more difficult formation of its com- 

 pounds, as is the case with the hydrocarbons of greater density. For though in 

 its relation to the acids, the paracyanic is much more stable than the cyanic acid, 

 yet in relation to heat the latter is by far the more permanent. 



We have therefore three compounds of carbon with nitrogen in the propor- 

 tion of two atoms to one. 



Cy . . . Cyanogen. 



CoN . . . The radical of the fuhninic acid. 



C8N4 . . Paracyanogen 

 forming with oxygen the acids CyO, CjNO, and CeN^O respectively. 



If we allow om-selves to reason from the obscure analogy of paracyanogen to 

 the hydrocarbons, we may expect a compound C N4 to fiU up the gap between it 

 and cyanogen, and which may possibly be a liquid. 



PoRTOBELLO, January 1830, 



