Copper arsenate is prepared by mixing a solution of soluble arsenate and a copper sulfate solution, either or both solutions, which contain sludge-forming impurities. It helps in forming a copper and arsenic-containing solution without precipitating the copper arsenate. The pH during the process is controlled at a value in the range of 1.7 to 2.2 to precipitate impurities. Precipitated impurities are removed & the copper and the arsenic-containing solution is neutralized with an alkaline substance, preferably dilute sodium hydroxide solution, to pH 3.2 to 4.2 that helps in precipitating copper arsenate.
Additional Information: Casting Properties In comparison to pure copper, the copper - arsenic alloys provide some advantages in casting. With an increased amount of arsenic, the melting temperature of the metal is decreased. The addition of 0.5% arsenic to copper prevents porosity even when casting under oxidizing conditions. It has been found that arsenic reduces the crystal size in castings that may result in the increase of tensile strength, as it increases with the decreasing grain size. With an addition of up to 1% arsenic, the formation of solid solution slightly increases the tensile strength, however, the ductility of material is not influenced.
Annealing: The improved work hardenability of copper alloys has found to be the advantage over pure copper if it is required to produce hard edges.
Hot Working: With up to 18% arsenic, the copper alloys have found to be highly ductile in hot working at 500 & 6000 C.
Copper with arsenic additions is primarily used in the manufacturing of boiler fireboxes.
Copper arsenate is also used as an ingredient to make Chromated Copper Arsenate (CCA), which is used, in the wood preservative industry.