Arsenic (As)
Arsenic (As)
Arsenic may have first been obtained in 1250 A.D., but preparation instructions were not published until 1649.
Arsenic is a brittle, crystalline, semimetallic solid that tarnishes in air. Elemental arsenic occurs in either yellow or gray metallic forms that have slightly different specific gravities. When heated, it rapidly oxidizes to arsenous oxide, which has a garlicky smell. Arsenic and its compounds are poisonous. Useful compounds include white arsenic, arsenic sulfide, Paris green, calcium arsenate, and lead arsenate.
Arsenic's uses include bronzing, pyrotechny, and for hardening and improving shot. Its compounds have been used in agricultural insecticides and poisons.