Nitro- Glycerine. 



95 



And first, I will briefly describe the mode of preparation. 

 Having prepared a mixture of nitric acid, specific gravity 

 1.500, three parts, with sulphuric acid, specific gravity 1.840, 

 six parts, we gradually introduce glycerine one part, whose 

 specific gravity is 1.250, taking care that the temperature does 

 not exceed at anytime 60°. A great deal of heat is evolved, 

 which is very apt to get the upper hand, and then the pro- 

 duct will contain oxalic acid, at the expense of the nitro- 

 glycerine which is sought. Moreover, it is difficult to 

 entirely deprive the nitro-glycerine when made, of the ni- 

 trous fumes (deutoxide of nitrogen) dissolved in it, by 

 washing. Availing myself of the well-known fact that 

 this gas, after being mixed with air, is less soluble than 

 in the nascent state, I contrived to agitate the mixture of 

 glycerine with the acids, by introducing a stream of cold 

 air pending the whole operation. I found this the least 

 dangerous mode of stirring, and by passing the air through 

 pipes surrounded with ice, succeeded in commanding the 

 temperature ; that is, the heat developed by the chemical 

 reaction was absorbed by the ice-cold air. These fumes, 

 which in all the imported nitro-glycerine, and indeed in all 

 the nitro-glycerine I have ever seen made by any other 

 process, contaminate the product, and involve subsequent 

 spontaneous decomposition, are, by the use of the stream 

 of ice-cold air, partly reconverted into nitric acid, and being 

 rendered less soluble by admixture with the air, the fumes 

 not reconverted are driven out of the acid mixture. Sub- 

 sequent washing with a still more powerful current of 

 air, so as to render the mixture of precipitated nitro- 

 glycerine and water a frothy emulsion, effectually removes 

 the last trace of these fumes, and thus the source of 

 subsequent spontaneous decomposition, terminating in 

 spontaneous explosion, is impossible. Mixed with the 

 water, however, there will be particles of organic matter, 

 and the nitro-glycerine will retain these, forming a 



