Since ancient times, man has known arsenic. Arsenic occurs frequently in some of the sulfur in the sulfides that are the principal ores of many heavy metals. When these ores are heated, the arsenic sublimes leaving ferrous sulfide. Arsenic has been used in agricultural insecticides and military poison gases as lewisite and adamsite. It has been increasingly used as a doping agent in solid state devices, such as transistors.
Gallium arsenide is used as a laser material that changes electricity directly into light.
Large quantities of arsenic are used in the manufacture of glass to eliminate a green color caused by impurities of iron compounds. Sometimes arsenic is added to lead to harden it. Bayer Corporation is a research-based company with major businesses in health care and life sciences, and chemicals.