96 



Nitro- Glycerine, 



scum, which, floating on the nitro-glycerine, is seen as a 

 precipitate beneath the supernatant water. The nitro- 

 glycerine is therefore now placed in six gallon stone jars, and 

 these are immersed in a large tank of water, maintained 

 at a uniform temperature of 60° to 70° for several days ; 

 the scum as it forms, and the sedimentary particles of 

 vegetable matter tying on the surface of the explosive, 

 but beneath the supernatant water, are removed, and the 

 explosive is now poured into paraffine-lined metallic vessels, 

 and crystallized by exposing to a temperature of 32° F. 

 This last process of crystallization separates a reddish un- 

 crystallizable liquid, dangerously explosive, every fifty-six 

 pounds of nitro-glycerine giving about three-quarters of an 

 ounce of this impurity, which is carefully drained off. If the 

 acids used be of full strength, and free from chlorine, etc., if 

 the glycerine used be free from impurity, the resulting pro- 

 duct is a nearly colorless, and very difficult to explode, nitro- 

 glycerine, which on analysis will be found to contain three 

 atoms of 1$2 O4, and hence I have distinguished it by the 

 term tri-nitro-glycerine. Such nitro-glycerine, I have ex- 

 posed for three years in an open shed, to sun, frost, snow, 

 without a trace of change. It is really difficult to explode. 

 A charge of powder will not explode it unless very closely 

 confined, and not always under those conditions. Car- 

 tridges have been filled with it, and hurled from a height 

 of sixty feet upon broken rocks, again and again, until the 

 cartridges are broken up, without exploding. I have 

 referred to our finally storing our nitro-glycerine in the con- 

 gealed state. Now all the books, especially German, de- 

 scribe nitro-glycerine when in the crystallized or congealed 

 state, as liable to explosion, by the slightest jar, or even 

 the scratch of a pin. In the winter of 1868-9, Wm. P. 

 Granger, Esq., then engineer in charge of the Hoosac tun- 

 nel, was desirous of blasting out the accumulated mass of 

 ice which had utterly closed up the race leading from the 



