Arsenic (symbol As) is a soft, brittle, poisonous element of steel-gray color and metallic luster. In atomic structure it is a semimetal, lacking plasticity, and is used only in alloys and in compounds. The bulk of the arsenic used is employed in insecticides, rat poisons, and weed killers, but it has many industrial uses, especially in pigments. It is also used in poison gases for chemical warfare.
Metallic arsenic is stable in dry air. When exposed to humid or moistened air, the surface first becomes coated with a superficial golden bronze tarnish, which on further exposure turns black. On heating in air arsenic will vaporize and burn to As2O3.
Dermatitis can result from handling arsenical compounds; hence, it is desirable to use impervious gloves or protective creams. The best preventative for dermatitis is strict personal hygiene. In areas where arsenical dusts and fumes are present, effective exhaust ventilation is necessary, or when impractical, a respirator should be used.
In the field of electronics, high-purity arsenic is finding an important use as a constituent of the III-V semiconductor compounds. The compounds of most interest are indium arsenide, which may be used for Hall effect devices, and gallium arsenide used for making diodes, transistors, and solar cells.
