(see that word Encycl.). The suffocating violence with which the oxy-muriat of potas- sia, when mixed with various substances, detonates, has been already noticed in this Supplement under the ar- ticle Chemistry, no 721, where the theory of these explosions is likewise given. But as several chemists seem to think that this salt, which decrepitates by fric- tion, and spontaneously takes fire when mixed with sul- phur, contains in itself the elements and phenomena of thunder, it will not probably be unacceptable to our readers to find, in this place, a distinct account of the various mixtures which produce its detonations. The following are the principal which have been discovered by Fourcroy and Vaquelin.
1. Three parts of the oxy-muriat of potas, and one part of powdered sulphur, rubbed together in a metal mortar, produce numerous successive explosions, resem- bling the cracking of a whip, or even as loud as the re- port of a pistol or a musket, according to the rapidity of the motion, and the force of the pressure made use of. A few grains of the same mixture, by being struck firmly upon an anvil with a hammer, occasion a report equal to that of a musket; and torrents of purplish light are seen about the anvil. If this mixture be thrown into concentrated sulphuric acid, it instantly takes fire, and burns, without noise, with a flame of a dazzling whiteness.
2. A mixture of three parts of this salt, half a part of sulphur, and half a part of charcoal, causes stronger explosions than the preceding, when rubbed in a mor- tar, and a louder noise when struck upon an anvil. Its flame also, when the mixture is made to explode, or when it is thrown into sulphuric acid, is more rapid, more lively, and of a redder colour, than that of the preceding.
3. A mixture of equal parts of oxy-muriat of potas and antimony in powder, explodes with noise by per- cussion; but produces only reddish sparks when thrown into sulphuric acid. If zinc be substituted in the place of antimony, a similar explosion takes place, accompa- nied with a white flame. Sulphuric acid has no effect upon this last mixture.
4. With regulus of arsenic, this salt explodes very violently by the stroke of a hammer; it inflames, with singular rapidity and brilliancy, by the contact of sul- phuric acid. In this last experiment there arises a smoke, which in the air takes the form of a crown, in the same manner as phosphorated hydrogenous gas does when it inflames spontaneously in a still atmosphere.
5. Sulphuret of iron or martial pyrites inflames rapid- ly, but without noise, when rubbed in a metal mortar with oxy-muriat of potas. This mixture, when struck upon an anvil, explodes violently, and with a red flame.
6. The red sulphuret of mercury or cinabar, and the sulphurated calces of antimony, explode with the oxy-muriat of potas by percussion, but they do not in- flame by sulphuric acid. The same thing happens when charcoal alone is mixed with this salt.
Any of the following substances, namely, sugar, gums, oils (both fixed and volatile), alcohol, ether, when mixed with oxy-muriat of potas, have the pro- perty of exploding very violently by the stroke of a hammer, and all of them send forth a brisk flame at the time of their explosion. The liquid combustible substan- ces above-mentioned are to be mixed with the salt in such a manner as to form a kind of paste. None of these mixtures explode or inflame by being rubbed in a mortar; but some of them inflame by being mixed with concentrated sulphuric acid, their combustion being slow and progressive.
8. All the substances above-mentioned, which, be- ing mixed with the oxy-muriat of potas, take fire and burn instantly, and with considerable noise, by the quick pressure of the strokes of a hammer, produce a much stronger explosion when they are so closely wrapped up in paper, two or three times doubled, as to be thereby compressed before they are struck.
9. An electric shock from a battery of large surface, charged by a strong electric machine, causes all the fore- mentioned mixtures to explode in the same manner as percussion, and their explosion is also accompanied by a bright light.
To the above-mentioned facts, the authors add, that it was already well known, that gunpowder would ex- plode by a violent blow, or very strong pressure; but they observe, that the stroke which is necessary for that purpose must be much stronger than that which suffices to produce an explosion in the above-mentioned mix- tures of combustible substances with the oxy-muriat of potas; and that its explosion is by no means so re- markable as that which is produced by the help of this new fact.