Solubilities of m-phthalic acid in petroleum ether and its binary solvent mixture of alcohol + petroleum ether

The solubility of m-phthalic acid in petroleum ether and in binary solvent mixture of ethanol + petroleum ether and 1-propanol + petroleum ether was measured in temperature range of 293–347 K using the analytical gravimetric method. The components and their compositions in the petroleum ethers used in this work were identified by GC–MS analyses. The solubility measurements show that petroleum ethers have much lower solubility to m-phthalic acid than ethanol and 1-propanol. In addition, the petroleum ether of higher boiling range shows much lower solubility than that of lower boiling range. For binary solvents the addition of petroleum ether into alcohol remarkably lower the solubility of the alcohol. The solubility data was correlated with the Apelblat equation and the Buchowski–Ksiazczak equation (the λh equation). Good agreements were obtained with the average absolute percent deviations of 1.55% and 3.32%, respectively. Furthermore, the mixed solvent systems were found to exhibit a synergistic effect (maximum solubility effect) on the solubility at high temperature, which may be attributed to the intermolecular association between the solute and the solvent mixture. The positive synergistic effect was well modeled by the modified Wilson equation.