In order to provide basic data for the crystallization of dl ‐methionine and understand the thermodynamic properties of dissolution, the solubility of dl ‐methionine in water was measured by gravimetric method from 294.05 to 347.05 K and the solubility at different pH values under temperature 302.95 to 342.05 K was determined by elemental analysis in this work. The experimental data show that the solubility of dl ‐methionine increases with increasing temperature as well as more acidic or basic pH values. The van't Hoff equation, modified Apelblat equation, λh equation, Wilson model, NRTL model, and UNIQUAC model were used to correlate the solubility data versus temperature. The melting temperature, enthalpy of fusion, enthalpy and entropy of dissolution were estimated from solubility data and it shows that the expression of solubility by enthalpy and entropy of dissolution gives more reasonable estimation and Wilson model gives a better correlation for these thermodynamic properties.

中文翻译：

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依赖于温度和pH值的dl-蛋氨酸的溶解度的测定和关联

为了提供dl-蛋氨酸结晶的基础数据并了解其溶解的热力学性质，采用重量法从294.05到347.05 K测量了dl蛋氨酸在水中的溶解度，并在302.95至250的温度下测量了不同pH值下的溶解度。在这项工作中通过元素分析确定了342.05K。实验数据表明，dl的溶解度蛋氨酸随着温度的升高以及酸性或碱性pH值的增加而增加。使用Van't Hoff方程，改良的Apelblat方程，λh方程，Wilson模型，NRTL模型和UNIQUAC模型将溶解度数据与温度相关联。根据溶解度数据估算了熔融温度，熔融焓，溶解焓和溶解熵，结果表明，由溶解焓和溶解熵表示的溶解度表示更合理，Wilson模型对这些热力学性质给出了更好的相关性。