FORMATION OF HYDROCYANIC ACID. 313 



degrees of oxidation of carbon, viz. carbon monoxide and 

 carbonic acid, gives off the same quantity of heat. These are 

 conjectures of some interest, and have been accepted by various 

 savants since they were first broached. 1 



12. However this may be, the figures actually obtained lead 

 us to conceive a very definite opinion, which is confirmed by 

 experiment. In fact, they show that the formation of hydro- 

 cyanic gas from cyanogen and hydrogen 



H + CN = HCN, gives off + 7-8 Gal. 



This formation is therefore exothermal ; a circumstance which 

 led to the suspicion that it might be effected directly, notwith- 

 standing the negative experiments that had been made previously 

 by Gay-Lussac. In fact, the direct combination of the two 

 gases was effected directly by means of time and heat alone, 

 and under conditions comparable with those in the synthesis of 

 the hydracids of the halogen elements properly so called. 2 



13. The synthesis of gaseous hydrocyanic acid from acetylene 

 and free nitrogen, a synthesis very easy to effect through the 

 action of the electric spark, as was discovered in 1868 



C 2 H 2 + N 2 = 2HCN, disengages + 2'1 Gal., 



a positive though very low quantity. 



14. As to the formation of hydrocyanic acid from ammonium 

 formate and formamide, which is the simplest type of a general 

 reaction in organic chemistry, viz. that for the formation of 

 nitrils, it is worthy of special attention. 



Let the reaction be as follows : 



NH 4 CHG 2 = HCN + 2H 2 0, 



the water and the acid being supposed to be separate. 



This reaction, if it could be effected with solid bodies at the 

 ordinary temperature, so as to produce water and liquid hydro- 

 cyanic acid, would absorb 137 Gal. Effected with the dis- 

 solved salt, it would absorb - 104 Gal. 



Let us again note the initial system 



H 2 C0 2 (pure), NH 3 (diluted), HC1 (diluted) ; 

 and the final system 



HCN (pure), HC1 (diluted), 2H 2 0. 

 We may pass from one to the other by two different methods. 



1 " Annales de Chimie et de Physique," 4 e se*rie, torn, xviii. pp. 161, 173, 

 and especially 175. 



2 Ibid., 5 e se'rie, torn, xviii. p. 378. The heat of formation of hydrocyanic 

 acid, admitted in the article quoted, was estimated, by means of the data then 

 known, at + 26'9 ; this is too high, but the sign of the phenomenon remains 

 the same, and, consequently, the preconceived idea of its beingsynthetic. 



\( UNIVERSITY 



