Schwartz P A, Paruta A N
J Pharm Sci. 1976 Feb;65(2):252-7. doi: 10.1002/jps.2600650219.
Equilibrium solubilities of the first four homologous alkyl p-aminobenzoate esters were determined in methanol, ethanol, and 1-propanol at 25, 33, and 40 degrees; the esters and the alcohols comprise separate homologous series. The solution process of a solute may be considered to be the summation of two sequential steps, melting and mixing, and the magnitude of solubility depends upon temperature and the extent of interactions between solute and solvent molecules. Quantitative solute concentrations, obtained from spectrophotometric analysis, were converted to mole fractions. Statistical analysis of the logarithmic mole fraction solubilities of the aminobenzoates, which were linear with respect to both reciprocal absolute temperature and the logarithm of absolute temperature, generated enthalpies and entropies of solution, respectively. The heats of fusion and the melting points of these aminobenzoates were determined to calculate their ideal solubilities. Excess free energies and partial molal free energies of each solution were calculated from the activity coefficients of the solutes; the thermodynamic elements for these systems are discussed.
测定了前四种同系对氨基苯甲酸烷基酯在甲醇、乙醇和1-丙醇中于25、33和40摄氏度时的平衡溶解度；这些酯和醇各自构成同系物系列。溶质的溶解过程可被视为两个连续步骤（熔化和混合）的总和，溶解度的大小取决于温度以及溶质与溶剂分子间相互作用的程度。通过分光光度分析获得的定量溶质浓度被转换为摩尔分数。对氨基苯甲酸酯的对数摩尔分数溶解度进行统计分析，其与绝对温度的倒数以及绝对温度的对数均呈线性关系，分别得出了溶解焓和溶解熵。测定了这些对氨基苯甲酸酯的熔化热和熔点以计算其理想溶解度。根据溶质的活度系数计算了每种溶液的过量自由能和偏摩尔自由能；并讨论了这些体系的热力学要素。
