Arsenic

Arsenic is an ancient metal often used in compounds as a poison.   Albertus Magnus may have isolated arsenic in 1250 C.E.   In 1649, Johann Schroeder, a German pharmacist, published two methods for its preparation.   Arsenic is used in bronzing, pyrotechnology and in improving the hardening and sphericity of shot.   It is used in several forms as an agricultural insecticide and poison and as a doping agent in transistors.   Gallium arsenide [GaAs] is used as a laser material to convert electricity into coherent light. ^{Lide 4-4}

It is found in the sulfide ores realgar, orpiment and, most commonly, mispickel, FeSAs. ^{Lide 4-4}