Copper(II) arsenate

Copper arsenate (Cu3(AsO4)2.4H2O, or Cu5H2(AsO4)4.2H2O), also called copper orthoarsenate or tricopper arsenate or tricopper orthoarsenate, is an insecticide used in agriculture. It is also used as a herbicide, fungicide, and a rodenticide. It is a blue or bluish-green powder insoluble in water and alcohol and soluble in aqueous ammonium and dilute acids. Its CAS number is or.

Copper arsenate hydroxide or basic copper arsenate (Cu(OH)AsO4) is a basic variant with CAS number. 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.

Copper arsenate is also used as a poison in slug baits.

Copper arsenate can also be a misnomer for copper arsenite, especially when meant as a pigment.