Leaching Tests on Copper-Chromium-Arsenic Preservatives

Tests of the leaching of CCA preservatives indicate that solution concentration, chromium content, solution acidity, and drying time of the treated material all have a definite influence on leaching resistance. Although leaching tests can be an important tool, the complex nature of the fixation of copper, chromium, and arsenic confounds the ability to predict the performance in service solely on the basis of laboratory leaching results. All leaching tests were carried out using pine sapwood sawdust as the test material. In each test, 2 grams of air-dry sawdust were placed in a small weighing bottle and 4 ml of the desired treating solution were added. The bottles were then covered and the treated sawdust was stored in the bottles for 3 days. At the end of this period the covers were removed and the material was allowed to air-dry at room temperature for 4 days. After drying the sawdust was leached for three 2-hour intervals using 200 ml of water each time, with some stirring of the solution during leaching. Total leaching time, therefore, was 6 hours and the total amount of leaching water used was 600 ml.

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