In 1649 Schroeder published two methods of preparing the element. Arsenic and its compounds are poisonous. Arsenic is used in bronzing, pyrotechny, and for hardening and improving the sphericity of shot. Marsh's test makes use of the formation and ready decomposition of arsine. Arsenic is finding increasing uses as a doping agent in solid-state devices such as transistors.
Gallium arsenide is used as a laser material to convert electricity directly into coherent light.