CHEMISTRY OF NITROGLYCERINE. 81 



Sulphuric acid, in the proportion used, would appear, therefore, to act less 

 energetically than hydrochloric acid on nitroglycerine. Concentrated sulphuric 

 acid in the cold seems to have almost no action, as is proved by the method 

 of the preparation of nitroglycerine. 



Action of Sulphuretted Hydrogen. — According to De Vrij,* an ethereal 

 solution of nitroglycerine is readily decomposed by sulphuretted hydrogen with 

 a copious precipitation of sulphur. 



In order to test the truth of this observation, I submitted two ten per 

 cent, solutions of nitroglycerine — the one in absolute alcohol, the other in 

 ether — to the action of a stream of sulphuretted hydrogen gas. But although 

 the gas was allowed to pass in a rapid stream through each solution for fifteen 

 minutes, yet not the slightest trace of decomposition occurred, as was evidenced 

 by no change of colour, and the absence of nitrous acid and precipitated sulphur 

 and other decomposition products ; even although, in the case of the alcoholic 

 solution, its temperature was raised to near the boiling point and the gas passed 

 for fifteen minutes longer. Nitroglycerine was precipitated abundantly from 

 both solutions on the addition of water. These experiments were more than 

 once made, and always with the same result. 



It must, therefore, be concluded, that sulphuretted hydrogen has no action, 

 or at most a very slow action, on pure nitroglycerine. The opposite experience 

 of De Vrij was probably due to his having used an impure nitroglycerine. 



Action of Alkaline Sulphides. — These act very energetically on nitro- 

 glycerine, and decompose it, if in alcoholic solution, as rapidly as alkalies alone 

 do. On adding a solution of ordinary sulphide of potassium, or sulphide of 

 ammonium, to an alcoholic solution of nitroglycerine, the mixture quickly 

 assumes a deep reddish-brown colour, and its temperature rises ; and the 

 action of the sulphide is completed with a sudden and most abundant 

 precipitation of sulphur in every part of the mixture simultaneously. No gas 

 is given off; and, contrary to expectation, after being boiled with excess of 

 the sulphide for half an hour, filtered to remove the sulphur, and treated with 

 acetate of lead and again filtered to remove the sulphuretted hydrogen of the 

 sulphide, it yielded evidence of the presence of nitrous acid to the extent of a 

 little less than half the proportion yielded by a purely alkaline decomposition. 

 It would appear, therefore, that the whole of the nitrous acid set free in the 

 decomposition of the nitroglycerine by the alkali of the sulphide is not acted 

 on by the sulphuretted hydrogen of the sulphide. For we may assume, since 

 sulphuretted hydrogen does not of itself attack nitroglycerine, that it is the 

 alkali of the sulphide which takes the initial step in the decomposition of the 

 nitroglycerine ; the sulphuretted hydrogen playing a subsidiary part, and merely 

 acting on the nascent products of the decomposition effected by the alkali. 



* De Vrij, Journ. PTiarm. [3], xxviii., 3 ; and Gmelin's Handbook of Chemistry, x. p. 562. 



