Copper arsenate (Cu3(AsO4)2.4H2O, or Cu5H2(AsO4)4.2H2O), also called copper orthoarsenate, tricopper arsenate, cupric arsenate, or tricopper orthoarsenate, is a blue or bluish-green powder insoluble in water and alcohol and soluble in aqueous ammonium and dilute acids. Its CAS number is 7778-41-8 or 10103-61-4.
Copper arsenate hydroxide or basic copper arsenate (Cu(OH)AsO4) is a basic variant with CAS number 16102-92-4. It is found naturally as the mineral olivenite. It is used as an insecticide, fungicide, and miticide. Its use is banned in Thailand since 2001.