Baird James K, Baker Jonathan D, Hu Baichuan, Lang Joshua R, Joyce Karen E, Sides Alison K, Richey Randi D
Department of Physics, ‡Department of Chemistry, and §Materials Science Graduate Program, University of Alabama in Huntsville , Huntsville, Alabama 35899, United States.
J Phys Chem B. 2015 Mar 12;119(10):4041-7. doi: 10.1021/jp511892b. Epub 2015 Feb 25.
Binary liquid mixtures having a consolute point can be used as solvents for chemical reactions. When excess cerium(IV) oxide is brought into equilibrium with a mixture of isobutyric acid + water, and the concentration of cerium in the liquid phase is plotted in van't Hoff form, a straight line results for temperatures sufficiently in excess of the critical solution temperature. Within 1 K of the critical temperature, however, the concentration becomes substantially suppressed, and the van't Hoff slope diverges toward negative infinity. According to the phase rule, one mole fraction can be fixed. Given this restriction, the temperature behavior of the data is in exact agreement with the predictions of both the principle of critical point isomorphism and the Gibbs-Helmholtz equation. In addition, we have determined the concentration of lead in the liquid phase when crystalline lead(II) sulfate reacts with potassium iodide in isobutyric acid + water. When plotted in van't Hoff form, the data lie on a straight line for all temperatures including the critical region. The phase rule indicates that two mole fractions can be fixed. With this restriction, the data are in exact agreement with the principle of critical point isomorphism.
具有低共熔点的二元液体混合物可作为化学反应的溶剂。当过量的二氧化铈与异丁酸 + 水的混合物达到平衡时，若以范特霍夫形式绘制液相中铈的浓度，在温度远高于临界溶液温度时会得到一条直线。然而，在临界温度的1K范围内，浓度会大幅降低，且范特霍夫斜率趋向负无穷大。根据相律，可以固定一个摩尔分数。在此限制下，数据的温度行为与临界点同构原理和吉布斯 - 亥姆霍兹方程的预测完全一致。此外，我们还测定了结晶硫酸铅（II）与碘化钾在异丁酸 + 水中反应时液相中铅的浓度。当以范特霍夫形式绘制时，包括临界区域在内，所有温度下的数据都位于一条直线上。相律表明可以固定两个摩尔分数。在此限制下，数据与临界点同构原理完全一致。
