电解质在混合溶剂中的活度系数及溶剂化数的研究——KClO_(4)-CH_(3)OH-非电解质体系

STUDIES ON ACTIVITY COEFFICIENTS AND SOLVATION NUMBERS OF ELECTROLYTES IN MIXED SOLVENTS-SYSTEMS OF KClO_(4) METHANOL AND NONELECTROLYTES

本文测定了KClO_(4)在甲醇-苯,甲醇-甲苯,甲醇-四氯化碳及甲醇-环己烷四个混合溶剂中的溶解度。使用A.D'Aprano[4]和C.W.Davies[2],报告的KClO_(4)及KNO_(3)在甲醇中的缔合常数,计算得“自由离子”浓度。盐的介质效应活度系数fMX以S_(o)/S_(m)或S_(o+)、D_(m±)的表示值趋近相等,与非电解质的摩尔分数X(Ne的关系符合经验公式:1gf_(MX)=kX_(Ne),这里S _(o)和S_(m)分别是盐在甲醇和混合溶剂中的溶解度;脚注(±)标识“自由离子”;k为常数。电解质的溶剂化数公式:n_(+)+n_(-)=-21gf_(MX)/1gφ_(ρ),对KClO_(4)在这些混合溶剂中的情况并不适用,这里n_(+)+n_(-)是正、负离子溶剂化数之和;φ_(p)是甲醇在混合溶剂中的体积分数。这个结果表明ClO_(4)^(-)的溶剂化层不是完全由甲醇分子所形成,非电解质也影响着ClO_(4)^(-)在这些溶剂中的溶剂化层。KNO_(3)的实验数据,溶解度公式和溶剂化数公式是引自李芝芬、黄子卿、刘瑞麟以前的论文[1]。

Solubility data of KClO_(4) in mixed solvents,namely,methanol-benzene,methanol-toluene,methanol-Carbontetrachloride and methanol-cyclohexane,are reported in this paper,The"free ion"concentrations of KC1O_(4) and KNO_(3) are calculated by using the association constants given by A,D’Aprano and C.W.Davies[2]of these salts in methanol,The medium activity coefficients fMX expressed in terms of S_(0)/S_(m)and(S_(0))±/(S_(m))±are approximately equal and related to rnol fraction XNc of nonelectrolytes in the mixed solvents by the following empirical formula:lg/MX=kX_(Ne) where So and Sm are solubilities of salts in methanol and mixed solvensts respectively;the Subscript±is used for the"free ion"and k is a constant.The formula for the Solvation number of electrolyte n_(+)+n_(-)=-2lgf_(MX)/lgφP is not valid for KClO_(4) in these Mixed solvents,where n_(+)+n_(-)is the sum of the solvation number of positive and negative ion;φp is the volume fraction of methanol in mixed solvents,This result indicates that the solvation layer of ClO_(4) is not entirely formed by the methanol molecules and the nonelectrolyte exerts some effects on the solvation layer too.experimental data of KNO_(3),formulas of the solubility and of Solvation numbers are quoted from the former paper of li,Huang and liu[1].