While noticing explosive compounds, it may not be improper to mention that of platinum, lately discovered by Mr. E. Davy. It explodes, when heated to 400 degrees, with a sharp report, similar to that produced by fulminating gold; but neither friction nor percussion will decompose it. It is formed by making a solution of platinum in nitromuriatic acid, and passing through it, sulphuretted hydrogen gas, until no further precipitation ensues. This precipitate, when collected, and digested in nitric acid, is converted into sulphate of platinum. This is dissolved in water, and liquid ammonia then added. The precipitate, now formed, is washed, and boiled in a solution of potassa, and, after having freed it from the adhering potassa, is suffered to dry. All fulminating ammoniacal compounds are analogous; and fulminating platinum, being composed of oxide of platinum, ammonia, and water, is decomposed in the same manner as these compounds. Fulminating platinum is composed as follows: Peroxide of platinum 82.5 _nearly_ 2 primes. Ammonia 9.0 1 ---- Water 8.5 2 ---- _Sect. XXIX. Of Detonating Powder from Indigo._ That indigo produces a detonating powder by treating it with nitric acid, is evident from experiment. As it produces a _purple_ light, it might, perhaps, be used advantageously in small fire-works. The process described by Dr. Thomson, (_System of Chemistry_, VOL. IV. p. 80, _Amer. edit._) is to boil one part of indigo in four parts of nitric acid. The solution will become yellow, and a resinous matter appear upon its surface. The boiling is to be stopt, and the liquor cooled. The resinous matter is then to be separated; and the solution evaporated to the consistence of honey. This is to be re-dissolved in hot water, and filtered, and a solution of potassa added, which will throw down yellow spicular crystals, consisting of _bitter principle_, combined with potassa. When the resin is again treated with nitric acid, the same bitter principle is produced. The spicular crystals, when wrapped up in paper, and struck with a hammer, detonate with a purple light. _Sect. XXX. Of the Fulminating Compound, called Iodide of Azote._