Detonating Powders, or Fulminating Powders. Certain chemical compounds, which, on being exposed to heat or friction, explode with a loud report, owing to one or more of the constituent parts assuming the elastic state with such rapidity as to strike the displaced air with great violence. The most common detonating powders (except gunpowder), are fulminating gold, and fulminating powder. This latter is made by triturating, in a warm mortar, three parts by weight of nitre, two of carbonate of potash, and one of flowers of sulphur. When fused in. a ladle and then set on the fire, the whole of the melted fluid explodes with an intolerable noise, and the ladle is commonly disfigured as if it had received a strong blow downwards. If a solution of gold be precipitated by ammonia, the product will be fulminating gold. This precipitate, separated by filtration, and washed, must be dried without heat, as it is liable to explode with no great increase of temperature; nor must it be put into a bottle with a glass stopper, as the friction of this would expose the operator to the same danger. Less than a grain held over the flame of a candle explodes with a very sharp and loud noise.
Fulminating silver may be prepared as follows: powder one hundred grains of nitrate of silver, put the powder into a glass vessel, and pour upon it first an ounce of alcohol, and then as much concentrated nitrous acid. The mixture grows hot, boils, and an ether is visibly formed, that changes into gas. By degrees the liquor becomes milky and opaque, and is filled with small white clouds. When all the grey powder has taken this form, and the liquid has acquired consistency, distilled water must be immediately added, to suspend ebullition and prevent the matter from being redissolved and becoming a mere solution of silver. The white precipitate is then to be collected on a filter, and dried. The force of this powder greatly exceeds that of fulminating mercury: it detonates in a tremendous manner on being scarcely touched with a glass tube, the extremity of which has been dipped in concentrated sulphuric acid. Fulminating mercury was discovered by Mr. Howard. A hundred grains are to be dissolved with heat in an ounce and a half by measure of nitric acid. The solution, when cold, is to be poured on two ounce measures of alcohol, and heat applied till an effervescence is excited.
As soon as the precipitate is thrown down, it must be collected on a filter, that the acid may not react on it, washed, and dried by a very gentle heat. It detonates with very little heat or friction. Three parts of chlorate of potash, and one of sulphur, triturated in a metal mortar, cause numerous successive detonations, like the cracks of a whip, the reports of a pistol, or the fire of musketry, according to the rapidity and force of the pressure employed. A few grains struck with a hammer on an anvil explode with a noise like that of a musket, and torrents of purple light appear around it. Six parts of the chlorate, one of sulphur, and one of charcoal, detonate by the same means, but more strongly, and with a redder flame. Sugar, gum, or charcoal, mixed with the chlorate, and fixed or volatile oils, alcohol, or ether, and made into a paste, detonate very strongly by the stroke, but not by trituration. Some of them take fire, but slowly and by degrees, in sulphuric acid. Fulminations of the most violent kind require the agency of azote or nitrogen, as we see not only in its compounds with the oxides of gold, silver, and platina, but also still more remarkably in its chloride and iodide, which form the two most violent detonating compounds known.
The first of these, viz. the chloride of azote, was discovered in 1812, by M. Dulong, but its nature was first investigated by Sir H. Davy, who was twice seriously wounded by explosions of the substance whilst operating upon it. It may be prepared as follows: put into an evaporating porcelain basin a solution of one part of nitrate or muriate of ammonia, in ten parts of water heated to about 100°, and invert into it a wide-mouthed bottle filled with chlorine. As the liquid ascends by the condensation of the gas, oily looking drops are seen floating on its surface, which collect together, and fall to the bottom in large globules: this is chloride of azote. By putting a thin stratum of common salt at the bottom of the basin, we prevent the decomposition of the chloride of azote by the ammoniacal salt. It should be prepared only in very small quantities. A small quantity of it thrown into a glass of olive oil, produced a most violent explosion, and the glass, although a strong one, was broken into fragments. It also detonates strongly when brought into contact with phosphorus and many of its compounds, with various fixed oils, with oil of turpentine, naphtha, fused potash, aqueous ammonia, nitrous gas, and various other substances, but not with sulphur or resin.
Iodide of azote may be most readily prepared by putting pulverulent iodine into common water of ammonia. It is pulverulent, and of a brownish black colour. It detonates from the smallest shock, and from heat, with a feeble violet vapour. When properly prepared, it frequently detonates spontaneously; hence, after the black powder is formed, and the liquid ammonia decanted off, the capsule should be left in perfect repose. Dr. Ure mentions, that in transferring a little of it from a capsule of platina to a piece of paper, the whole exploded in his hands. It should therefore be prepared with the greatest care, and in only very small quantities, and should not be preserved.