Solubility of the System 2-Propanol-Water-Aluminum Sulfate

Abstract

Solubility and tie-line equilibria are observed for the system 2-propanol-Water-aluminum sulfate at 5, 15, 25, 35° C. And crystal structure of aluminum sulfate in a state of equilibrium is investigated. Effect of temperature on the phase diagrams is very small. When the weight fraction of water in the mixed solvent is in the range from ca.0.941 to ca.0.811, the solubility of aluminum sulfate decreases with rise of temperature (Fig.3 and Fig.4)
Several methods of tie-line estimation in the literature are examined. The method proposed by Hand gave straight lines (Fig.5). But these lines are different in various temperatures. The method proposed by Nakamura also gave straight lines which were independent of temperature (Fig.6). Besides these, the method proposed by Major and Swenson is acceptable. The other method gave curved lines. Log plot of XB/Xc against XB/XA gaves straight lines. In the case of liquid-liquid equilibrium with solid phase (Table 1), the theoretical ratio of solvent to excess water is obtained by the solvent addition crystallization method. This method gives lower ratio with fall of temperature (Fig.8). The real ratio of solvent to excess water will be larger than the theoretical one.