The present invention is directed to copper arsenate compositions which are useful in preparing chromated copper arsenate wood preserving formulations. The copper arsenate compositions are slurries of insoluble copper arsenates in an aqueous solution of copper arsenates. The copper arsenate slurries have a mole ratio of As.sub.2 O.sub.5 to CuO of from about 0.3:1 to about 0.9:1 and are readily soluble in chromic acid to form chromated copper arsenate solutions. The copper arsenate slurries are prepared by reacting copper metal with arsenic acid in the presence of an acid catalyst and an oxidizing agent.