98 ANNUAL OF SCIENTIFIC DISCOVERT. 



for the time, at least, they have abandoned the use of powder, and 

 the quarries have been entirely worked by nitroi^lycerino for six 

 weeks. 



From the first, we have considered that the nitroglycerine sliould 

 be pi-ejiared on the spot. It always seemed to us the transportation 

 of an explosive compound of sucli frightful i)ower ought not to be 

 allowed either by laud or watei*. Tiie terrible accidents which 

 have happened at Aspinwall and at San Francisco justify these 

 fears; and the transportation of nitroglycerine should be posi- 

 tively forljiddi'U. 



After having, with M. Keller's assistance, studied in my lal)ora- 

 toi-y the ditfcrent processes of the prciparatiou of nitroglycerine 

 (mixtures of glycerine with concentrated sulphuric acid and 

 nitrates of potash and soda, or with nitric aiids of dilferent concen- 

 trations), we have determined on the following method of manu- 

 factm-e, which is performed in a wood cabin, constructed in one 

 of the quarries : — 



Preparation of Nitroglycerine. — We begin by mixing in an 

 earthenware vessel placed in cold Avater some fuming nitric acid 

 at 49° or 5U° Baume (1.51 — 1.53) with twice its weight of the 

 strongest sulphuric acid. Tliese acids are purposely prepared at 

 Dieuze, and sent on to Saverne. At the same time, we evaporate 

 in a pot some commercial glycerine free from both lime and lead, 

 until it makes 30° or 31° Baume (1.26 — 1.27). This concentrated 

 glycerine should, after cooling, have a syrupy consistence. 



The workman then tlu'ows thirty-three hundred grammes of a 

 mixture of suli)huric and nitric acids, well cooled, into a glass fiask 

 (a pot of earthenware or a capsule of porcelain might equally be 

 employed) placed in a trough of cold water, and then he slowly 

 pours into it, stirring it continually, five hundred grammes of gly- 

 cerine. The thing to be observed is tlie avoidance of any sensible 

 heating of the mixture, wliich would determine a tumultuous 

 oxidization of the gh'cerine, and the production of oxalic acid. 

 For this reason it is, that the vessel in whicli the transformation of 

 the glycerine into nitroghcerine takes ^^lace should be constantly 

 cooled externally by cold water. 



When the materials ai"e thoroughly mixed, the whole must be 

 left for five or ten minutes ; then pour the mixture into five or 

 six times its volume of cold water, to which a rotatory movement 

 must first be imparted. The nitroglycerine precij^itates very 

 rapidlj', under the form of a heavy oil, which is collected by 

 decantation into a vessel ; then wash it with a little water, which 

 is in its turn decanted ; pour the nitroglycerine into bottles, and it 

 is x-eady for use. 



In this state, the nitroglycerine is still slightly acid and watery ; 

 but this is of no importance, since, as it is emj^loyed soon after 

 its preparation, these impurities in no degree prevent detonation. 



Properties of Nitroglycerine. — Nitroglj-cerine is a yellow or 

 brownish oil, heavier than water and insoluble in it, but soluble 

 in ether, alcohol, etc. 



Exposed to a prolonged but not intense amount of coldness, it 

 ci-ystallizes in long needles. A violent shock best causes it to 



