High-pressure solubility of disperse dyes in near- and supercritical fluids: measurements up to 100 MPa by a static method

Solubilities of the disperse dyestuff 1,4-bis-(octylamino)-9, 10-anthraquinone (AC08) in near- and supercritical CO2 were measured spectroscopically in the visible range with a static analytical method. The concentrations were determined in the temperature and pressure ranges from 286 to 325 K and 6 to 90 MPa (13 isotherms). In addition, the solubility behavior was investigated along the liquid-vapor boundary curve starting at 282.5 K until near the critical temperature. As a rule, it was found that the concentrations become higher with increasing pressures and densities at a constant temperature. The isotherms of the dyestuff examined show intersection points in the concentration versus pressure plots which can be explained by a density effect. Supplementary experiments were carried out for AC08 in CClF3 at two temperatures (309 and 315 K) and in a pressure range from 9 to 78 MPa. In this particular case higher pressures are needed to reach the same concentration as for the solvent CO2 at a given temperature. (C) 1998 Elsevier Science B.V.