An experimental technique for measuring high solubilities of dyes in supercritical carbon dioxide

The solubilities of colour index (C.I.) disperse orange 3, red 324, blue 79 and quinizarin were measured at the temperatures of 353.2, 373.2, 393.2 K between 18 and 30 MPa with a ‘flow method’ conceived for determination of high solubilities in order to avoid the flow instability problems connected with dye precipitation. The comparison of results with the literature underlines the advantage of this new technique: higher solubility values are obtained especially at the most severe operating conditions. Experimental data for disperse orange 3 were also compared with similar results obtained by the authors using a ‘batch method’ in a previous work. The comparison of the results shows how the ‘flow method’, even though adapted for high solubility measurements, reveals to be the simplest and more efficient technique to evaluate dye solubility in supercritical fluids