166 



DR SAMUEL BROWN ON PARACYANOGEN. 



cyanogen with the nitrogen and carbon of the solid residue ; and from this obser- 

 vation it was concluded that the residue in question was a carburet of nitrogen, 

 containing less nitrogen than cyanogen. 



In A.D. 1829, Professor JOHNSTONE published some interesting analyses of this 

 substance, from which it appeared to contain nitrogen and carbon in the very 

 same ratio as cyanogen itself. His results were received with some distrust ; but 

 only on account of the singularity of the inference to which they conducted, iso- 

 meric bodies being then comparatively unknown. Some analyses of LIEBIG'S did 

 not at first bring out exactly the same proportions as those of Mr JOHNSTONE, but 

 in the summer of A.D. 1835, they examined the subject together in the presence 

 of Dr GEEGOKY, and their results accorded with the former observations of the 

 British chemist, who subsequently published an elaborate memoir on paracyano- 

 gen in the Transactions of the Royal Society of Edinburgh for 1838. That memoir 

 contains satisfactory and numerous analyses of the carbonaceous matter under 

 consideration, all of which tend to establish the proposition that it is isomeric 

 with cyanogen, and that, consequently, the volume of cyanogen produced from 

 cyanuret of mercury by heat is less, exactly in proportion as the quantity of para- 

 cyanogen left in the retort is greater. The analyses were made by decomposing 

 paracyanogen by means of oxide of copper and bichromate of potash, collecting 

 the gaseous products, removing the carbonic acid from different volumes of the 

 mixture, and finding the proportional volumes of nitrogen ; for example, with the 

 former reagent a mixed product wr u, of which 



90.0 vols. left 32.6 v. nitrogen, 



92.9 ... 30.1 

 293.0 ... 98.0 

 and with the latter, 



94.5 vols. left 33.5 v. nitrogen, 

 129.0 ... 43.0 

 108.0 ... 36.0 

 175.0 ... 58.5 



These ratios, taken in connection with the ascertained composition of cyanuret of 

 mercury, prove that the subject of analysis is composed of nitrogen and carbon in 

 the proportion of 1 : 2. The composition of gaseous cyanogen is N 4- C 2 . 



II. Properties of Paracyanogen. We are indebted to Professor JOHNSTONE 

 for all that has been published about the properties of paracyanogen. Prepared 

 by heat from the cyanuret of mercury, it is a brown solid, more or less dark- 

 coloured and dense according as it is procured at higher or lower temperatures, 

 varying in these respects from the condition of a loose, nut-brown, hygrometric 

 powder, to that of a compact, black scoria. It cannot, however, be made to assume 

 the latter form without the loss of some of its nitrogen; the more suddenly it is raised 



