Three or four grains of this powder, heated on a knife, will explode with a loud report. The temperature required for its explosion is between 230° and 300°. Ten or twelve grains will penetrate a copper-plate, of the thickness of a playing card. The facility with which this powder explodes, is increased by drying. If it be heated until it becomes black, the slightest touch will cause a detonation. This powder is composed of oxide of gold, ammonia, and a portion of chlorine; and, during its detonation, water, nitrogen and chlorine are evolved, the gold being revived. The presence of ammonia is necessary to give to gold the property of fulminating. Fulminating gold accordingly loses this property, the moment the ammonia is separated. Concentrated sulphuric acid, melted sulphur, fat oils, and ether have this effect. The discoverer of fulminating gold was a German Benedictine Monk, who lived about the year 1413. Basil Valentine has described the preparation of it very accurately. He recommends, however, mixing sal ammoniac with aqua fortis, the old mode of making aqua regia, and distilling the mixture; then putting in the gold in leaf. After the acid is saturated, he adds _oleum tartari_, or _sal tartari_ (carbonate of potassa) dissolved in water; and the precipitated _calx_, thus obtained, when collected, washed, and dried in the open air, will fulminate. In this process, it is evident, that the aqua regia, prepared with sal ammoniac, contains ammonia, and, when the gold is dissolved, and the potash added, the oxide of gold separates, and, from the composition of the powder, must combine with a portion of ammonia, and hence produce fulminating gold. He remarks, that distilled vinegar digested on fulminating gold, destroys its fulminating properties, and observes also, that care must be taken to prevent its explosion. He also knew that sulphur would have the same effect. Bergman (_Treatise on Pulvis Fulminans_) describes the process employed by Valentine; and Beckman (_History of Inventions_, v. iii. p. 132,) observes, that, after the time of Valentine, Crollius, who lived in the last half of the 16th century, was well acquainted with fulminating gold, and made its preparation more generally known. In the _Oswaldi Crollii Basilica Chymica_, 4to, p. 211, published at Frankfort, in 1609, the process is also to be found. He calls it _aurum volatile_, and speaks of its being useful in medicine. Beguin, however, appears to have given it the appellation of _aurum fulminans_, if we judge from his _Tyrocinium Chymicum_, 12mo, printed in 1608. _Sect. XXVIII. Of Fulminating Platinum._