Recently guncotton has been employed as an absorbent for nitro-glycerine, and it is claimed that in this form the explosive gives as good results as the pure chemical itself; a second quality dynamite is sometimes made, composed of nitrate of soda UP, paraffin 7, charcoal 4, and nitro glycerine 20 per cent.; or nitrate of potash 71, paraffin 1, charcoal 10, and nitro-glycerine 18 per cent. Lithofracteur is a mixture containing soda saltpetre 4, coal 12, kieselguhr 30, sulphur 2, nitro-glycerine 52 per cent. Duolin is a mixture of 30 flue sawdust, 20 saltpetre, and 5,.) per cent.
nitro-glyoerine. A number of such mixtures may be made, as any dry powder may be taken as an absorbent, but they are of no special value, inasmuch as it is improbable that any useful effect is obtained from ingredients, other than the nitro-glycerine ; those containing such salts as nitrate of soda are objectionable from their liability to exudation.
In packing cartridges of dynamite for export the cartridges aie separately rolled up in parchment paper, and are then packed into a cardboard box containing 5 lb. Ten of these are packed in black tarred paper fastened with cement, and the whole enclosed with a stout wooden box.
Picrates.—Picric acid formed by the action of nitric on carbolic acid possesses marked explosive properties ; if heated it takes fire and burns rapidly without explosion, but all the picrates are exploded with violence by heat or blows. When used as explosive agents, they arc mixed either with nitrate or chlorate of potash. Chlorate of potash mixed with picrate of potash, the most violent explosive of the picrates, is very powerful, but so sensitive to friction or percussion as to render it practically useless ; with nitrate of potash instead of chlorate a less violent mixture is obtained, but one still sensitive to accidental explosion. A mixture of saltpetre and picrate of potash, either with or without the addition of charcoal, has been made in quantities for use in blasting, but its sensitiveness has led to many accidents, which prevent its general use. Picrate of ammonia has very different properties to those of the potassium salt ; when a light is applied to it it burns with a strong smoky flame, and it is not very sensitive to either blows or friction ; when mixed with salt petre it may be used as a substitute for gunpowder. The picrate is prepared from picric acid and ammonia, the acid is dissolved in water and ammonia added to neutralization. This is repeated several times, and the liquid allowed to stand, when the ammonium picrate crystallizes out in large quantities, the crystals, drained and dried, are then ready for use. The mother liquid may be used for the preparation of several lots of the ammonium salt, until it becomes charged with impurities, when it may be otherwise treated, or thrown away ; in this way a considerable amount can be expeditiously prepared with little labour and without much loss. With the addition
of a small quantity of charcoal to the piorate and saltpetre, a mixture may be made which, when carried through the usual gunpowder processes, affords a powder of good grain, less hygroscopic than gunpowder, and possessing valuable properties as an explosive.
Fulminates.—The highly dangerous and strongly explosive salts of fulminic acid are all called fulminates, with them are also classed the powerful and dangerous chloride and iodide of nitrogen and other similar substances ; the only two of these which are of any commercial value are fulminate of mercury and fulminate of silver, the former of which is almost exclusively used in the preparation of percussion caps, for fire-arms, and detonators for use with the nitro-glycerine and nitro-chemical compounds, such as dynamite, lithofracteur, tonite, guncotton, and the like Fulminate of silver being used in minute quantities for children's toy cracks, pistol cracks, bon bons and similar trifles. Fulminate of mercury is prepared according to the German method by dissolving 1 part of mercury in 12 parte of nitric acid, sp. gr. ; to this solution 16.5 parts of absolute alcohol is added by degrees ; heat is then applied till the effervescence and cloud of gas disappears, when as the action becomes more violent, an equal quantity of alcohol to that before employed is gradually added ; the product affords 112 per cent. of the mercury used. Another method is to dissolve by gentle heat 10 parts of mercury in 100 parts nitric acid, sp. gr. and, when the solution has reached the temperature of 54° (130° F.), to slowly pour it through a glass funnel into 83 parts of absolute alcohol ; as soon as the effervescence ceases, and the white fumes are not evolved, the whole is filtered through double paper, washed through cold water, and dried over hot water at a temperature not exceeding 100° (212° F.), the fulminate is then carefully packed in paper boxes or corked bottles; the product is about 130 per cent. of the weight of the mercury used. The latter method is the safest and cheapest, but in any case the manufacture is a very dangerous operation, and wherever practicable, fulminate of mercury should be kept damp, when it is practically harmless. When dry, its crystals are small and of a brownish-grey sparkling colour, it is soluble in boiling water, and deposits in pearly grey spangles as the solution cools ; a pint of boiling water will dissolve 67 grains of fulminate, it explodes violently both by friction and percussion, with a peculiar cracking noise, but only burns with a sudden flash when ignited unconfined in the open air ; commercial fulminate of mercury is usually largely adulterated with chlorate of potash.