The anhydric acid cannot be isolated; but the salts (particularly of potassa and baryta) have been extensively employed in the manufacture of explosives, by mixing with combustible materials. Even the heat of percussion or friction causes them when so mixed to detonate. A few centigrammes of chlorate of potassa rubbed in a mortar with sulphur or sulphide of antimony, will explode loudly and perhaps shatter the mortar. A chlorate should never be mixed by rubbing with a combustible substance. A mixture of chlorate of potassa with sugar, sulphur, sulphide of antimony, or similar substances, may be ignited by sunlight alone, or by a drop of sulphuric acid. On this principle were based the matches (now out of fashion) which were tipped with a mixture of chlorate of potassa and sugar, and were ignited by pressing them upon asbestus, saturated with sulphuric acid. During the French revolution, it was attempted to replace nitre in gunpowder with chlorate of potassa; but the mixture was too explosive for artillery purposes. Berthollet's experiments at Essonne, in 1792, were stopped by a terrible explosion; he had a narrow escape, and several were killed. A cane, striking powder on the floor, was the cause.

Percussion caps were formerly filled with gunpowder out of which the nitre had been leached, and to which this chlorate had then been added. Sir William Armstrong uses a mixture of amorphous phosphorus and chlorate of potassa as a percussion powder for discharging ordnance. A mixture of equal weights of black sulphide of antimony and chlorate of potassa is generally employed for this purpose.-White gunpowder, introduced in 1849 by Augendre, for bronze -ordnance and shells, is composed of 28 parts yellow prussiate of potassa, 23 parts loaf sugar, and 49 parts chlorate'of potassa. According to Wagner, the gaseous products of complete combustion should be 47.4 per cent., and the solid residue (cyanide and chloride of potassium and carburet of iron) 52.6 per cent. The gases from 100 grammes would amount, at 0° C. and 7G9 mm. barometric pressure, to 40,G80 cubic centimetres; and at 2604.5° C, the estimated temperature of combustion, to 431,102 cubic centimetres. The cost and corrosiveness of this powder have prevented its adoption.-Blake's "safety explosive," patented in England, consists of one part sulphur and two of chlorate of potash. These substances are kept dry and separate, and mixed when required.

The powder burns slowly when ignited, but its explosion is effected by means of a detonating tube, containing the compound itself, fulminating mercury, and ordinary powder. The last is ignited.-A blasting powder is made at Plymouth, England, consisting of tan bark soaked in chlorate of potash and covered with powdered sulphur. It is said to burn slowly in the open air, but to explode with great energy when confined.-Explosive paper is prepared by impregnating paper with a mixture of 9 parts chlorate of potassa, 4 1/2 of nitre, 3 1/4 of ferrocyanide of potassium, 3 1/4 of powdered charcoal, 5/100 of starch, 6/100 of chromate of potassa, and 80 of water which has been boiled about an hour. The paper, when dry, cannot be exploded by jar or percussion, or by a temperature less than that of its combustion. Experiments with it in Austria have given good results.- Chloride of nitrogen is perhaps the most terrible explosive known to chemists. Dulong, who discovered it in 1812, and lost an eye and several fingers on the occasion, kept the discovery a secret, lest other chemists should repeat his perilous experiments. The unfortunate result was that Davy, who subsequently made the same discovery, was also injured.

It is sometimes unintentionally produced in the treatment of ammoniacal solutions with chlorine. In such cases the chemist, having discovered its presence, quietly retires, locks the laboratory, and leaves the dreadful intruder to spontaneous and harmless decomposition, which takes place in the course of a day or two. Hypochloric acid, in gas or liquid form, is scarcely less dangerous.-Picrate of Potash Powders. Picric acid, obtained by the action of nitric acid upon carbolic acid, is a compound of carbon, nitrogen, hydrogen, and oxygen, the formula, as given in Wagner's Technology," being C6H3(N02)30. Its salts are explosive per se, and have been used in torpedoes. Their preparation has given rise to some frightful explosions; one at the Sorbonne, in 1869, killed five persons, and wounded many more. Dessignolle's powder for blasting is a mixture of picrate and nitrate of potassa, to which for a gunpowder charcoal is added. Sulphur is unnecessary. The advantages claimed for it are the harmless character of the products of combustion (nitrogen, aqueous vapor, and carbonate of potash), and the control of its power by variation of the percentage of the picrate.

Ten grades are manufactured, containing from 8 to 20 per cent. of this substance, the lowest being equal in effectiveness to common powder.-Ammoniakrut is a new powder invented by the Swedish chemist Norrbin, and believed to resemble the foregoing, but to contain picrate of ammonia instead of potassa. It is black, doughy, and damp; is ignited with difficulty by flame; explodes under percussion; does not congeal at ordinary temperatures; has an explosive energy exceeding even that of dynamite; but is said to be liable to decomposition, to attract moisture and lose power when stored, and to be useless if once frozen. It leaves no solid residue.-Fulminates. The compounds of cyanogen comprise many highly explosive substances, among which the fulminates, or salts of fulminic acid, are the most important. Fulminic acid (Lat. fulmen, a thunderbolt) is, according to the most modern formula (Kekule's), a nitrocompound of the group C4H3N (acetonitril), and hence called nitro-acetonitril. One of the hydrogen atoms is replaced with an atom of NO4, giving for the acid C4(N04)H2N. In the salts the hydrogen is replaced with a metal; thus the fulminate of silver is C4(N04)Ag2N. This hypothesis explains the fact that the fulminates react very differently from the cya-nates (mono-,di-, and tribasic), all of which have the same proportions of C, N, and metallic base, but doubtless different atomic arrangements.