The chemistry of chromated copper arsenate II. Preservative-wood interactions

The reactions which cause chromated copper arsenate preservative to fix str ongly into wood are reviewed. A number of the mechanisms proposed in the li terature appear chemically implausible. A new model is advanced in which th e final fixation products are dominated by chromium (III) arsenate, chromiu m (III) hydroxide, and copper (II)- wood carboxylate complexes. Carboxylate groups should be generated in large numbers in the reduction of chromium ( VI) by primary alcohol groups in lignin and carbohydrate fractions, or in t he oxidative degradation of lignin. The model is supported by a recent X-ra y absorption fine structure analysis.