ARSENIC is the name applied in popular language to a well-known poisonous sub stance, arsenious acid (q.v.), but, strictly speaking, the term is restricted to the metal, of which the symbol is As and the equivalent is 75.0. The metal A. is rarely found free in nature, but in a state of combination it occurs largely (see ARSENICAL MINERALS). The metal is generally prepared from arsenious acid by mixing it with its own weight of charcoal, placing the mixture in a well-covercd crucible, and subjecting the whole to heat, when the metal set free by the charcoal rises, and condenses in the upper part or cover of the crucible. Metallic A. is very brittle, can easily be reduced to pow der by hammering, or even pounding in a mortar; and when a freshly-cut surface is examined, it presents a brilliant dark steel-gray lustre, which, however, readily tarnishes on exposure to the air. The metal, as such, is not considered poisonous, but when intro duced into the animal system, it is there faintly acted upon by the juices, and in part „dis solved, at the same time exhibiting poisonous properties. When heated in the open air,
it burns with a peculiar bluish flame, and emits a characteristic alliaceous odor. The only use to which the metal A. is applied in the arts is in the manufacture of leaden shot of the various sizes, when its presence in small quantity in the lead renders the latter much more brittle than it ordinarily is. Of all the compounds of A. the most impor tant is the one already alluded to—viz., arsenious acid, which is an oxide of A. With sulphur, A. forms two important compounds: realgar a red, transparent, and brittle substance, which is employed in the manufacture of the signal-light called white Indian fire; and orpiment or Icing's yellow, a cheap pigment of a yellow color. With hydrogen, A. forms arseniuretted hydrogen a very poisonous gas, and one which has been fatal to several chemists.