Solutions containing mixtures of water soluble copper salts and sodium nitrite have been shown to be capable of producing leach resistant copper treatments when impregnated into timber. A rapid leaching trial showed that copper fixation levels of 85-90% were possible which compared well with the fixation level obtained with conventional hexavelant chromium containing systems in the same test regime. The fixation process appears to be dependant only upon the presence of copper and nitrite ions and is not affected significantly by the nature of the copper salt or other components present. Optimum fixation is obtained with a molar ratio of copper to nitrite ion of between 1:4 and 1:5.

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