The well prepared fulminate of mercury is in the form of bright, little crystals of a brownish-gray color; they appear transparent when placed on a glass watch-crystal and humected with a few drops of water. They dissolve without residue in 130 parts of boiling water, and the solution deposits crystals by cooling.

The fulminato of mercury decomposes with flame and explosion, by a shock, or when heated at 870°. It disengages nitrogen, carbonic acid, and vapors of water and mercury.

The conditions of explosibility in the fulminate of mercury are very important to study from the point of view of the salubrity. Thus we would remark that the explosion is much more easy under the influence of the shock, when the striking bodies are harder. The shock of wood against wood, or even iron against wood docs not determine the explosion. It occurs very rarely between iron and lead; oftener, but with difficulty, between glass and glass, marble and marble. It is always produced between iron and iron, less easily between iron and bronze, iron and copper; on the contrary, by rubbing, it is easily determined between two wooden plates, less easily between two iron or two marble plates.

The largest crystals are those which detonate the most easily. When the fulminate of mercury is humected with 5 per cent of water, the part which is stricken alone detonates, and the inflammation is not spread to all the mass.

When you add 30 per cent of water, you can rub the fulminate, without any danger, on a marble plate.

All these circumstances are important, and ought to be known by every manufacturer, foreman, workman, etc., for they furnish useful information, and diminish the dangers of the fabrication of the fulminating powders.