Investigations on the solubilities of some disperse azo dyes in supercritical carbon dioxide

Abstract The solubilities of three disperse azo dyes, 4-( N , N -dimethylamino)-4′-nitroazobenzene (D 1 ), 4-( N , N -diethylamino)-4′-nitroazobenzene (D 2 ) and Parared (D 3 ) in supercritical carbon dioxide have been measured at different temperatures (308, 318, 328, 338, 348 and 358 K) and in the pressure range of 122–355 bar. The measurements were performed using a simple static method. As evidenced from the experimental results, the solubilities increase with increasing density of supercritical CO 2 . The solubilities in supercritical CO 2 decrease in the order D 2 >D 1 >D 3 , which parallel the order of their relative melting points; the higher the melting point, the lower the solubility. The equilibrium solubility data were correlated using a semiempirical model. The calculated results show satisfactory agreement with the experimental data.