萘在1-1价小离子盐水溶液中活度系数的研究(V)

STUDIES ON ACTIVITY COEFFICIENTS OF NAPHTHALENE IN AQUEOUS SALT SOLUTIONS(Ⅴ)

本文用紫外分光光度法测定了25℃下萘在LiBr、NaBr,KBr、NH_4Cl、NaF及KF盐水溶液中的活度系数f。将萘的lgf分别对六种盐的浓度c_S作图,得到通过原点的直线,符合Setschenow盐析公式,直线斜率就是盐析常数k。本文还计算了萘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,Debye-MacAulay理论和McDevit-Long公式的计算值都较实验值大2—3倍。Conway等人理论的计算k值对不同盐差别很小,而实验值彼此之间的差别却很大。对体积大的非电解质,色散力对盐析常数的影响不可忽略。本文对Bockris公式进行修正,计算结果表明,它能较正确地指出盐效应的次序及盐析常数的符号。内压力理论改进公式的计算结果不仅能预言盐析常数的符号,也能指出盐析常数大小的顺序,理论值与实经值符合较好。

The activity coefficients f of naphthalene in the aqueous salt solution were determined at 25℃ by spectrophotometer. The salts used are LiBr, NaBr, KBr, NH_4Cl, NaF and KF.When lgf is ploted vs. c_s for these salts, the results obtained are all straight lines The salting-out constants κ were calculated.We have calculated the salting-out constants of naphthalene in six aqueous salt solutions by the formulas of (1) Debye-McAulay, (2) Conway-Desnoyers-Smith, (3) McDevit-Long, (4) scaled partical theory, (5) modified Bockris' dispersion energy theory and (6) modified internal pressure theory.In the systems having ions and nonelectrolyte molecules both of large size, the effect of dispersion forces can not be neglected. Modified Bockris' theory indicates signs of salting-out effect correctly.For large nonelectrolyte molecules, the equation of modified internal pressure theory gives results in better agreement with the experiment than others.