FULMINATING POWDERS, is a name given to those chemical compounds which are decomposed with such ra pidity as to produce a report, with other signs of The most conspicuous of these bodies are the amtnoniiirets of gold, silver, and mercury ; the precipitate formed by al cohol from nitrate of mercury, which has been called ful minating mercury, and the powder formed with potash, ni tre, and sulphur, called fiulvis .fulminans.
The first of these compounds, viz. ammoniuret of gold, is prepared by dissolving gold in a mixture of equal parts of nitric and muriatic acids ; dilute the solution with three times its volume of water ; and acid pure aquA ammonia by a little at a time, so letng as any precipitate is thrown down. Beyond this point, more amnion:a would i cdissolve the pre cipitate, which is the substance to be obtained.
In this process, the ammonia combines with the oxide of gold, forming an insoluble yellowish powder. This is to he separated front the liquid, washed with pure water, and dried at a low heat upon filtering paper. When dry, it must be cautiously put into a clean bottle, the mouth of which must not be corked, but slightly covered with paper. Fulminating gold, thus prepared, has the following pro perties. It explodes by a smart blow from a hammer, or when sharply triturated in a mortar. It is also decompo sed with sudden violence when heated to about 250°. By all these means, the explosion is accompanied with a loud report, and the disengagement of elastic fluids, and is ac companied with light and heat. The hydrogen of the am monia combines with the oxygen of the oxide of gold, form ing water, which is dispersed in the form of highly elastic steam. The azote of the ammonia, at the same time, is evolved, acquiring great expansive force by the disenga ged caloric.
Fulminating silver is prepared by first dissolving pure silver in nitric acid. By adding lime water to this solu tion, the oxide of silver is precipitated ; this oxide is now separated by filtering and washing. Pure ammonia is now to be poured. upon the oxide, and allowed to remain upon it twelve hours. The liquid part is now to be carefully decanted off, and a black powder remains, which is the am moniuret of silver, the substance in question. It is now to
he transferred with great caution, and by a little at a time, into as many portions of clean filtering paper. This pow der is even capable of exploding, while moist, by a blow. When dry, it becomes so susceptible of decomposition as to explode by the slightest touch. The liquid separated from the powder, on being heated in a glass veto; t, affords azotic gas ; and small opaque crystals soon begin to appoar, of great brilliancy, having metallic lustre. These crystals are doubtless the true compound of ammonia with oxide of silver, owing their production in the crystalline form to their solubility in water. On being touched they detonate, even when covered with the liquid in which they are formed.
The same explanation which has been applied to the ful minating gold will apply to the substance in question, al though the reason is not very obvious why the fulminating silver should be more easily decomposed. Perhaps it will be found, that the silver contains twice the quantity of oxy gen with the gold, and that the oxide of the former com bines with twice the quantity of ammonia.
Fulminating silver has been lately used in making what have been called fulminating halls. These consist of small bubbles of glass, a little larger than a pea. A small por tion of this compound is introduced at a little opening left for the purpose. The glass is then covered with paper. Any force capable of breaking the bubble produces the ex plosion.
Mercury, from its weak affinity for oxygen, forms a de tonating compound with ammonia, and other bodies con taining much hydrogen. The first of these compounds is formed, by digesting strong aqua ammonia upon the red oxide of MercUry for ten or twelve days. At the end of this time, the oxide assumes lt white colour in crystal'. having the form of small scales. In this form, it fulmihate., by heat similar to fulminating gold. Its effects, however, are not so strongly marked as the two former, and it gradu ally loses its fulminating property by keeping. The am monia is separated, leaving the red oxide unc•anged.