Describes procedures for determination of copper, chromium and arsenic in preservatives and in treated timber containing those water-borne preservative compositions which consist essentially of copper, chromium and arsenic compounds, in sawdust, wood flour, or thin sections. There is no inter-elemental interference during the determinations and the procedures are specific for arsenic even in the presence of phosphorus compounds, includes sections on atomic absorption spectrometric method, colorimetric method and test report.