NITROGLYCERIN. 281 



We see that the thermal effect varies inversely with the dilu- 

 tion, just as in the case of ethyl-sulphuric acid, and those acids 

 allied to it. 



The formation of nitric ether is, in this respect, analogous 

 to that of those from organic acids, in which case their pro- 

 duction causes absorption of heat, whether the bodies in ques- 

 tion be in solution or in a pure state. 1 



But, on the contrary, the formation of nitric ether from con- 

 centrated acid gives rise to disengagement of heat. This 

 opposition results from the great difference of energy existing 

 between nitric acid in the pure state and that diluted with 

 water. 



3. The formation of nitric ether from its elements 



C 2 (diamond) + H 5 + N + 3 = C 2 H 4 (HN0 3 ) (liquid), 



gives off + 49-3 Cal. for 91 grms., or, for 1 grm., 542 cal. 



4. Decomposition. Nitric ether may be distilled with great 

 regularity, but care must be taken to avoid all local overheating. 

 The approach of a flame, or even a temperature of about 300, 

 causes the ether to explode with violence. A terrible accident, 

 which happened at a chemical works at St. Denis, has shown the 

 dangers attendant upon the handling of large quantities of this 

 ether. The products of this explosion have not been analysed. 

 The oxygen contained in the compound is, moreover, insufficient 

 to oxidise the carbon and hydrogen, even supposing the first 

 body to be converted only into carbon monoxide. Admitting the 

 following reaction 



C 2 H 4 (HN0 3 ) = 2CO + H 2 + 3H + N, 



the composition of the liquid ether, with the formation of liquid 

 water, would give off + 71 '3 Cal. for 91 grms. If the ether 

 and water were in the gaseous form, the figures would be 

 slightly different, amounting, for 1 grm., to 787 cal. 



5. The heat of total combustion of nitric ether by means of 

 pure oxygen 



[2C 2 H 4 (HN0 3 ) + 70 = 4C0 2 - 5H 2 - N 2 ], 

 gives off + 311-2 Cal. for 91 grms., or 3420 cal. for 1 grm. 



2. Nitroglycerin, C 3 H 2 (HN0 3 ) 3 = 227 grms. 



1. Nitroglycerin was prepared in a calorimeter, by means of 

 nitrosulphuric acid, and under conditions similar to those 

 recently described by M. Champion ; conditions under which 

 the product amounts to only four-fifths of the theoretical value, 

 owing to unavailable secondary oxidations. Quantities of 1*201 

 grm. and T934 grm. of glycerin were experimented upon. It 

 1 " Annales de Chimie et de Physique," 5 e serie, torn. ix. p. 344. 



