Cotton powder explodes at the same temperatures as gun-cotton, and lithofracteur at the same temperature as kieselguhr dynamite.
Section VI.—Some Varieties of the Nitro-cellulose and the Nitro-glycerine Compounds.
Nitrated Gun-cotton.
—It has been shown that gun-cotton contains an insufficient quantity of oxygen for its complete combustion. To furnish that which is wanting, gun-cotton has sometimes incorporated with it a certain proportion of nitrate of potash, or of nitrate of baryta. This compound, which, it will be observed, is at once a chemical compound and a mechanical mixture, is known as “nitrated gun-cotton.”
Cotton Powder, or Tonite.
—The explosive which is now well known as “tonite” or “cotton powder,” is essentially nitrated gun-cotton. It is produced in a granulated form, and is compressed into cartridges of various dimensions to suit the requirements of practice. The convenient form in which tonite is made up, ready to the miner’s hand, has greatly contributed towards bringing it into favour. But irrespective of this, the fact of its being so highly compressed as to give it a density equal, or nearly equal, to dynamite gives it a decided advantage over the other nitro-cotton compounds as they are at present used.
Schultze’s Powder.
—In Schultze’s powder, the cellulose is obtained from wood. The wood is first sawn into sheets, about 1⁄16 inch thick, and then passed through a machine, which punches it up into grains of a uniform size. These are deprived of their resinous matters by a process of boiling in carbonate of soda, and are further cleansed by washing in water, steaming, and bleaching by chloride of lime. The grains, which are then pure cellulose, are converted into nitro-cellulose in the same way as cotton, namely, by being treated with a mixture of nitric and sulphuric acids. The nitro-cellulose thus produced is subsequently steeped in a solution of nitrate of potash. Thus the finished compound is similar in character to nitrated gun-cotton.
Lithofracteur.
—Lithofracteur is a nitro-glycerine compound in which a portion of the base is made explosive. In dynamite, the base, or absorbent material, is, as we have said, a silicious earth, called “kieselguhr.” In lithofracteur, the same substance is used; but in addition, a mixture of nitrate of baryta and charcoal, a kind of gunpowder, is introduced. The object of employing this explosive mixture is to increase the force of the explosion, the kieselguhr being an inert substance. Obviously this object would be attained if the explosive mixture possessed the same absorbent power as the kieselguhr. But unfortunately it does not, and, as a consequence, less nitro-glycerine is used. Thus what is gained in the absorbent is lost in the substance absorbed. The composition of lithofracteur varies somewhat; but its average proportion of ingredients are the following:—