Arsenic

Arsenic, chemical element, symbol As; for physical constants see Periodic Table. Arsenic has been known since ancient times. Elemental arsenic was first described by Albertus Magnus in the 13th century. Sometimes found native, it occurs widely in the form of arsenides, from which the element is obtained as a byproduct. Arsenic is a soft and brittle gray element with a metallic luster which sublimes without melting; several other allotropic forms have been reported. The metal conducts electricity moderately well. Arsenic is used in bronzing, hardening, and improving the sphericity of metal shot, and in pyrotechnics. Compounds of arsenic are used as agricultural insecticides and poisons. Arsenic in high purity is used as a doping agent in solid-state devices. Gallium arsenide is used as a laser material to convert electricity directly into coherent light. Arsenic and its compounds are poisonous.