Mr Johnston on a solid form of' Cyanogen. 81 



ferent arrangement may take place ; and I shall here state one 

 fact, which inclines me to think that such a change of arrange- 

 ment has taken place. 



Alcohol newly saturated with cyanogen gives no precipi- 

 tate with bichloride of mercury. But when it has become of 

 the reddish brown colour already mentioned, it throws down 

 a precipitate which at first is brown, but afterwards assumes a 

 reddish tint. With nitrate of silver it gives a precipitate which 

 is entirely characteristic. This precipitate at first is brown like 

 that from mercury, but it gradually darkens, and, together, 

 with the supernatant liquid, becomes finally of a beautiful pur- 

 ple. Aqueous cyanogen gives with nitrate of silver a dirty 

 black, and hydro cyanic acid a white becoming black, from both 

 of which this purple precipitate is very distinct. We may infer 

 then that the precipitflw^ is also distinct. Yet the carbon and 

 azote exist in it in the same proportions; for the precipitate 

 from mercury detonated with chlorate of potash gave me gases 

 in the proportion of 



2 volumes carbonic acid 

 to 1 azote. 



The nature of this class of compounds, however, I intend, 

 on some future occasion, more fully to investigate. * 



II. Of the proto-carburet of azote. 

 I have already alluded to the change of composition which 

 the bicarburet undergoes when subjected to a heat sufficient 

 to volatilize and drive off the mercury with which it is mixed 

 when obtained from the decomposition of the cyanide of that 

 metal. The nature of this change will be seen from the fol- 

 lowing results : — 



1. An indeterminate portion, after heating in this manner, 

 was decomposed by chlorate of potash. The results were, 



inch. 

 Carbonic acid, =r .93, or 3 atoms. 



Azote, = .62, or 2 atoms. 



* By a series of experiments, yet unpublished, I find the cyanide of mer- 

 cury to consist of two atoms cyanogen, and one atom mercury. It is pos- 

 sible that these precipitates may consist of one atom cyanogen or its ele- 

 ments to one atom mercury. See Art. XIX. in this Number. 



NEW SERIES. VOL. I. NO. I. JULY 1829- F 



