1868. ] its Claims as a New Industrial Agent. 151 
large scale. They are at Lauenburg (Prussia), the one just referred 
to as outside the city of Hamburg, at Stockholm, Christiania, 
Helsingfors, and New York. In order to reduce to a minimum 
the danger which is alleged to attend the manufacturing operations, 
the establishment first mentioned is wholly built in an artificial 
excavation in and beneath the level of the earth; and thus any 
explosion which may possibly result in the works will be confined 
to the works themselves, and will exert no damage in a lateral 
direction. This plan might well be adopted in building gunpowder 
mills. As an indication that the manufacture of nitro-glycerine is 
conducted onan exact system, on rigidly scientific principles, it may 
be mentioned that in only one instance has there been an explosion 
in any of the five works mentioned, and even that was but a very 
slight one. The manufacture has not yet been introduced into 
England, although we carry on mining operations, quarrying, 
railway-tunnelling, &c., on such a stupendous scale as is not 
excelled in any country of similar extent. Why English capitalists 
have not taken to it we know not; but of this we feel assured, 
from what we know of the extent to which nitro-glycerine is 
already in use amongst us, that the manufacture of this substance 
is yet destined to become a profitable undertaking in this country, 
when its use will doubtless be very greatly extended. 
As might almost be inferred from the name, and, indeed, as has 
already been mentioned, nitro-glycerine results from the action of 
nitric acid on glycerine; at all events, the chemistry of the opera- 
tion is essentially limited to the reaction of those two substances on 
each other. In practice, it is found necessary to use sulphuric acid 
in conjunction with the nitric acid, as in the production of gun- 
cotton. ‘The essential details of the chemical transformation are 
the following, according to M. Kopp and various other chemists :— 
Fuming nitric acid (sp. gr. about 1°52) is mixed with twice its 
weight of the strongest sulphuric acid, in a vessel which is kept 
cool by being surrounded with cold water. When this acid mixture 
is properly cooled, there is slowly poured into it rather more than 
one-sixth of its weight of syrupy glycerine; constant stirring is 
kept up during the addition of the glycerine, and the vessel con- 
taining the mixture is maintained at as low a temperature as 
possible by means of a surrounding of cold water, ice, or some 
freezing mixture. It is necessary to avoid any sensible heating of 
the mixture, otherwise the glycerine is to a large extent transformed 
into oxalic acid. When the action ceases, nitro-glycerine is produced. 
It forms on the surface as an oily-looking fluid, the undecomposed 
sulphuric acid forming the subjacent layer, owing to its greater 
specific gravity. The whole mixture is then poured, with constant 
stirrmg, into a large quantity of cold water, when the relative 
specific gravities become so altered that the nitro-glycerine subsides 
