二氯苯在盐水溶液中活度系数的研究

STUDY ON THE ACTIVITY COEFFICIENTS OF m-DICHLOROBENZENE AND p-DICHLOROBENZENE IN AQUEOUS SALT SOLUTIONS

本文采用紫外分光光度法测定了25.00±0.001℃下间位和对位二氯苯在HCOONa,CH_3COONa,(NH_4)_4SO_4,MgSO_4和Na_2SO_4水溶液中活度系数(f).它们的lgf-C关系符合Setschnow盐效应公式.本文还计算了二氯苯在盐水溶液中盐析常数的各种理论值,并对各种理论值进行对比.对于Debye-MacAulay理论(DMT),小离子盐的计算值与实验值相差较少,大离子盐相差则多;Conway-Desnoyers-Smith(CDST)理论计算值不理想;定标粒子理论(SPT)与实验符合程度最差;改进后的内压力理论(XIPT)其理论计算值与实验值较为吻合;Bockris色散力理论改进后计算比较简单,可以判断盐效应的符号,盐析顺序基本正确.

The activity coefficients of m-dichlorobenzene and p-dichlorobenzene in aqueous salt solutions have been determined at 25℃ by using spectrophotometric method. The salts used are HCOONa,CH3COONa, (NH4)2SO4,MgSO4,Na2SO4. The relation between lgf and Cs are in agreement with Setschenow experimental formula.The experimental results are compared respectively with the calculation results of Debye-MacAulay (DMT) and Conway-Desnoyers Smith (COST) electrostatic theories, Scaled particle theory (SPT), internal pressure theory (IPT), modified internal pressure theory, and modified Bockris's dispersion energy theory.In the systems having both ions and nonelectrolyte molecules in large size,the effect of dispersion forces can not be neglected and modified Bockris's theory indicates signs of salting-out effect correctly.For laege nonelectrolyte molecules, the equation of modified internal pressure theory gives results in better agreement with the experiment than others.