Measurement of the solubility of metal complexes in supercritical carbon dioxide using a UV–vis spectrometer

A new apparatus based on the circulation method was developed to measure the solubility of metal complexes in supercritical carbon dioxide (scCO2) at a wide range of temperatures and pressures. A UV–vis spectrometer, which was connected to a small saturation cell through optical fibers, was used to determine solubility. The solubilities of cobalt(III) acetylacetonate (Co(acac)3) and chromium(III) acetylacetonate (Cr(acac)3) in scCO2 were measured to check the validity of both the apparatus and the method and to accumulate new solubility data. The solubility data for Cr(acac)3 obtained in this study were in good agreement with the data reported in the literature.The measured solubilities of Co(acac)3 and Cr(acac)3 were also correlated with the empirical equation including the three adjustable parameters, based on the equation proposed by Chrastil. The parameters were determined by fitting the equation to the experimental data for each metal complex and the calculated results closely replicated the experimental data.