Investigations on the solubility of anthraquinone dyes in supercritical carbon dioxide by a flow method

The solubility of 1,4-bis-(n-propylamino)-9,10-anthraquinone in supercritical CO2 was measured spectroscopically by a flow method. Isotherms were recorded for temperatures and pressures from 305 to 340 K and from 7.5 to 20 MPa, respectively. Within the range of the experiments, the equilibrium concentrations become higher with increasing pressures and densities at constant temperature. In the concentration vs. pressure plot the isotherms show intersection points, which can be explained by a density effect.