In terms of practical applications it is important to collect accurate solubility data at any temperature and pressure in a supercritical fluid. We have been developing a process for detoxifying environmentally hazardous waste, namely chromated copper arsenic-(CCA-) treated wood, using supercritical CO, This is because, there is an increased awareness of possible problems caused by waste CCA-treated wood, leading to the need to develop a technique for extracting hazardous components from wood. We focused on copper compounds and used a flow-type apparatus to measure the solubility of a model copper compound fixed in wood. The model compound we used in this study was CuHAsO4, which is believed to exist in CCA-treated wood. After proving the accuracy of our apparatus by measuring naphthalene solubility in supercritical CO2 the solubility of CuHAsO4 was measured at 308 and 363 K for 14.7 and 24.5 MPa. It was found that the value was of the order of 10(-8)-10(-9), and that it was possible to dissolve CuHAsO4 in supercritical CO2 at a concentration of 2-6 x 10(-5) g kg(-1)-CO2. A solution model coupled with the Flory-Huggins equation was then used to correlate the experimental data. Relatively good agreement was obtained between the experimental data and the data calculated with this method. The validity of this correlation model was confirmed by applying it to the correlation of the reported solubility of copper chelate complex. (C) 2002 Elsevier Science B.V. All rights reserved.