Composition and solubility of precipitated copper(II) arsenates

► By mixing solutions of Cu2+ and HAsO42− solid phases are formed in a wide pH range. ► Five different stoichiometric compositions were found. ► Two of the solid phases formed in 0.1 M NaCl contained Na+. ► Stability constants for all solid phases have been determined. ► Aqueous complexes containing Cu2+ and AsO43− ions could not be detected.