Disclosed is a method of preparing compositions comprising submicron particles of a metal salt. The method comprises providing an aqueous alkaline solution comprising a metal, one or more ligand that forms a soluble complex with the metal under alkaline conditions, and optionally one or more dispersant； and admixing the solution and a source of carbon dioxide to reduce the pH of the solution such that submicron particles of a metal salt precipitate. Also disclosed are compositions prepared by the method. Also disclosed is a method of treating a substrate, such as lumber, comprising applying the compositions and substrates treated by the method.
