This element is no longer available.
Arsenic appears in three allotropic forms: yellow, black and grey; the stable form is a silver-grey, brittle crystalline solid. It tarnishes rapidly in air, and at high temperatures burns forming a white cloud of arsenic trioxide. Arsenic is a member of group Va of the periodic table, which combines readily with many elements.
The metallic form is brittle, tarnishes and when heated it rapidly oxidizes to arsenic trioxide, which has a garlic odour. The non-metallic form is less reactive but will dissolve when heated with strong oxidizing acids and alkalis.
Arsenic compounds are used in making special types of glass, as a wood preservative and, lately, in the semiconductor gallium arsenide, which has the ability to convert electric current to laser light. Arsine gas AsH3, has become an important dopant gas in the microchip industry, although it requires strict guidelines regarding its use because it is extremely toxic.
During the 18th, 19th, and 20th centuries, a number of arsenic compounds have been used as medicines; copper acetoarsenite was used as a green pigment known under many different names.