1879.] Hydrocyanic Acid in the Electric Arc. 



189 



ammoniacal sub- chloride of copper ; while, at the same time, a wash- 

 bottle containing water gave distinct evidences of the presence of 

 hydrocyanic acid. 



Experiment 3. — Hydrogen flame burning alone gave no sulphides or 

 hydrocyanic acid, the condensed water in a small bulb gave nitrites. 



Experiment 4. — Air drawn through the negative carbon gave con- 

 siderable quantities of hydrocyanic acid, which was greatly increased 

 by extracting the gases through the positive carbon. Air was aspirated 

 at the rate of about one litre per minute. 



Experiment 5. — -The same carbons used with de Meriten's magneto- 

 machine gave no result. 



Experiment 6. — Carbons purified in chlorine and hydrogen gave 

 with de Meriten's nothing ; with Siemens' and a draught of air 

 through the negative pole, a small quantity of hydrocyanic acid, but 

 a larger yield when the positive was used. The gases extracted after 

 the absorption of the hydrocyanic acid contained acetylene. If the 

 carbons are not purified, sulphuretted hydrogen is always found along 

 with other gases. 



The inference to be drawn from the above experiments is that the 

 high temperature of the positive pole is required to produce the re- 

 action, which is in all probability the result of acetylene reacting with 

 free nitrogen, as when induction sparks are passed through the mixed 

 gases, viz. — 



C 3 H 3 + N 2 =2HCN", 



and that the hydrogen is obtained from the decomposition of aqueous 

 vapour, and the combined hydrogen in the carbons. It is possible that 

 traces of alkaline salts in the carbon poles may favour the formation 

 of hydrocyanic acid, but, as all attempts to purify the poles so as to 

 stop the reaction failed, lam inclined to believe it is a direct synthesis. 

 The acetylene reaction is one of the many remarkable syntheses dis- 

 covered by Prof. Berthelot of Paris. The presence of sulphuretted 

 hydrogen is doubtless due to the reduction of the sulphates, invari- 

 ably present in the ash of the carbon. 



A more complete examinai ion of the various reactions to be brought 

 about by means of the Siemens arc, and with poles of varied composi- 

 tion, and in presence of different gases, will be communicated to the 

 Society in a subsequent paper. 



My thanks are especially due to Messrs. Ansdell and Cottrell, 

 assistants in the Royal Institution, for their valuable aid. 



