CHEMISTRY OF NITROGLYCERINE. 85 



acids. The highest yield of nitroglycerine is that of N., where 234 parts of 

 nitroglycerine were procured from 100 parts of glycerine. Now, glycerine, 

 C 3 H 3 .(OH) 3 , ought theoretically to produce 246 per cent, of tri-nitrate of 

 glyceryl, C 3 H 5 .3(O.N0 2 ). Making allowance for inevitable loss from 

 various intelligible causes, it may, therefore, be fairly deduced that the experi- 

 mental yield of nitroglycerine strongly favours nitroglycerine being regarded 

 as the tri-nitrate. If it were the tri-nitrite, C 3 H 5 .3(0.NO), the theoretical 

 yield would be 194 per cent. ; if the di-nitrite, C 3 H 5 .H0.2(O.NO), 163 per 

 cent.; and if the mono-nitrate di-nitrite, C 3 H 5 .(O.N0 2 ).2(O.NO), 211 per cent. 

 The actual yield very distinctly exceeds any of these. 



With regard to the conclusions of practical and commercial importance 

 which may be drawn from these various methods of preparing nitroglycerine, 

 it is to be observed that there is a distinct advantage, as is generally recognised, 

 in employing fuming nitric acid (compare (F) and (G) with (K) ) ; that where 

 fuming nitric acid is used, no benefit is to be obtained from the employment of 

 fuming sulphuric acid (compare (L) and (M) with (K) and (N) ); that two parts 

 of ordinary sulphuric acid to one part of fuming nitric acid appears to give as 

 good a yield as any other proportion of acids, and quite as large a yield as 

 when more sulphuric acid is used (compare (N) with (K) ) ; and that the yield 

 is not to any considerable extent increased by allowing the acids and glycerine 

 to remain in contact for some time after mixture, as some chemists have 

 advised (compare (F) with (G), and (L) with (M) ). 



Characters of Nitroglycerine. — I have been somewhat surprised to find 

 that a large number of contradictory statements exist as to the ordinary physical 

 characters of nitroglycerine. Whilst a few authors describe it as colourless, 

 by others it is referred to as a pale yellow oil, even in the most authoritative 

 modern works on Chemistry, as Fehling's Neues Handworterbuch der Chemie* 

 and Beilstein's Handbuch der Organischen ChemieA Now nitroglycerine is per- 

 fectly colourless when pure. As obtained from dynamite, it is certainty yellow, 

 but the colour is due to decomposition having taken place, which, I believe, is 

 to little or no extent spontaneous in character, but rather proceeds from the 

 presence of a little of the weak soda which is invariably employed in the manu- 

 facture of nitroglycerine for the purpose of removing the traces of the acids. 

 The soda neutralises the acids, but it at the same time decomposes the nitro- 

 glycerine, and imparts the colour so commonly ascribed to it as an inherent 

 property. Nitroglycerine washed with distilled water has in my possession 

 never become in the slightest degree coloured, even although kept in an open 

 capsule, freely exposed to the air, but away from dust, for two months ; in 

 stoppered bottles it has not during the last seven months showed the least sign of 

 decomposition. Even in solution in water, or in alcohol, it keeps almost equally 

 well. More than one author states that it decomposes and becomes red on 



* Bd. iii. 1878. f S. 529, 1881. 



