Disodium hydrogen arsenate
Disodium hydrogen arsenate is the inorganic compound with the formula NaHAsO7HO. The compound consists of a salt and seven molecules of water of crystallization although for simplicity the formula usually omits the water component. The other sodium arsenates are NaHAsO and NaAsO, the latter being called sodium arsenate. Disodium hydrogen arsenate is highly toxic. The salt is the conjugate base of arsenic acid. It is a white, water-soluble solid. Being a diprotic acid, its acid-base properties is described by two equilibria: