An arsenate (compound) is some compound that contains the arsenate ion : AsO₄^3- . Arsenate is much like phosphate. In acid conditions we have arsenic acid, H₃AsO₄; in weakly acid conditions we have the dihydrogen arsenate ion, H₂AsO₄^-; in weakly basic conditions we have hydrogen arsenate ion HAsO₄^2-; and finally, in basic conditions, the arsenate ion AsO₄^3-.