3S4 Essay upon the Compounds of Cyanogen. 



5. That it is a compound of ferrocyanic acid and peroxide of 

 ii'on, and like all other salts of the same base, contains 1.5 atoms of 

 acid + 1 atom of base — and 



6. That the following is the only constitution which can be recon- 

 ciled with the above facts : 



Atoms. Atoms. 



C 3 cyanogen, 78 



1.5 ferrocyanic acid < 1.5 iron, 42 



(1.5 hydrogen, 1.5 



, -J r ■ O iron, 28 



1 peroxide oi u'on < , c .c% 



^ (1.5 oxygen, 13 



1 water \\ ^S^"' ? 



I 1 hydrogen, 1 



170.5 representative number. 



Argento-cyanic acid. — This name I take the liberty of proposing 

 for the peculiar acid which M. Just Liebig first separated from How- 

 ard's fulminating silver, and which he described in the Ann. de 

 Chimie, fee. under the name of ' fulminic acid.' In a subsequent 

 essay, which was the joint production of Liebig and Gay-Lussac, a 

 number of experiments are recorded, which tend to elucidate its ul- 

 timate constitution, but do not seem to me capable of justifying the 

 inference that has been drawn from them, that the compound is a 

 supercyanice* of silver. When lime water is poured upon the fulmi- 

 nating compound, decomposition ensues, and oxide of silver is sepa- 

 rated. When this has perfectly subsided, the liquid is to be decant- 

 ed, and on the addition of nitric acid, a white precipitate falls, which 

 is the fulminic or argento-cyanic acid. In this process we may sub- 

 stitute for lime water, any of the other alkalies or earths, with the ex- 

 ception of ammonia, which holds the oxide of silver in solution, and 

 gradually gives rise to another well known detonating compound — 

 that discovered by Berthollet. 



The argento-cyanic acid is a white powder, slightly soluble in cold, 

 but more so in boiling water, and from either solution it may be ob- 

 tained in crystals. It reddens litmus, and is capable, as we have al- 

 ready seen, of combining with and neutralizing bases. With pot- 

 assa and soda it forms crystalline salts, of a disagreeable metallic 



* In the essay alluded to, which appeared before Serullas had announced the dis- 

 covery of the cyanic acid, the compound was called a supercyanate of silver. 



