Solubilities of cobalt(III) and chromium(III) acetylacetonates in supercritical carbon dioxide at elevated temperatures

The solubilities of cobalt(III) and chromium(III) acetylacetonates (Co(acac)3 and Cr(acac)3) in supercritical carbon dioxide (scCO2) were measured at high temperatures to accumulate new experimental data and to clarify the temperature dependency of solubility across a wide range of temperatures. An apparatus based on a static method was newly developed by connecting a UV–vis spectrometer with optical fibers to determine the solubility. The solubilities of both Co(acac)3 and Cr(acac)3 increased with increasing temperature at a constant CO2 density. Moreover, the relationships between the logarithm of CO2 density and that of solubility were almost linear for both metal complexes at the experimental conditions. On the other hand, the isobaric curves for the solubilities had local minimum values on the temperature–solubility plots at low pressures.