In the past, farmers have used toxic chemicals such as calcium arsenate, Paris green, dichlorodiphenyltrichloroethane, and toxaphene to rid their cotton crops of insects.
Their oxidation products include an array of arsenates, selenates, and selenites.
Volume 4 of the Handbook of Mineralogy is, like its predecessors, an invaluable reference work, this time on essentially all the arsenates, phosphates, vanadates, and uranates known through 1999.
Problems arise when chemical reactions change the arsenates into arsenites, which don't bind tightly to other minerals and can therefore enter the underground water supply.
