物理化学学报 >> 1985, Vol. 1 >> Issue (04): 304-307.doi: 10.3866/PKU.WHXB19850402

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介绍一种改进内压力盐效应公式的计算方法

谢文蕙; 姬泓巍; 李万杰   

  1. 北京大学化学系
  • 收稿日期:1985-02-28 修回日期:1985-05-17 发布日期:1985-08-15

THE CALCULATION METHOD OF A MODIFIED EQUATION OF THE INTERNAL PRESSURE SALT EFFECT THEORY

Xie Wenhui; Ji Hongwei; Li Wanjie   

  1. Department of Chemistry, Peking University, Beijing
  • Received:1985-02-28 Revised:1985-05-17 Published:1985-08-15

Abstract:

Some assumptions were made for the modified equation of the internal pressure theory originally suggested by McDevit and Long~[2].
κ_s={V~0_n(V_s-V~0_s)}/(2.303RTβ_0)·a/(a+b) (1)
When the distance between ion and nonelectrolyte molecule in aqueous salt solution is calculated, the ionic hydration should be considered for the larger nonelectrolyte molecules; and the nonelectrolyte molecule must be excluded from the primary solvation shell of the ion. For 1-1 electrolytes, we assume that: (a) Latimer's radii are used instead of the radii of ions, i.e., r_L~+=r_P~+_P+0.085 (nm), r~-_L=r~-_P+0.010 (nm), where r_P is the Pauling′s radius; (b) a in equation (1) is the average of the radii of cation and anion, i.e., a=1/2(R~-_L+r~-_L); (c) b is the radius of the nonelectroiyte molecule, i.e., b=1/2(V_n/N)~1/3, in which V_n is the molar volume of the nonelectrolyte, N is the Avogadro′s number. In order to test these assumptions, it has been calculated for the salting-out constant of five benzene derivatives and four fatty acids in the solution of alkaline halides by the theories of (I) Debye-McAulay, (II) Conway-Desnoyers-Smith, (III) McDevit-Long and (IV) modified McDevit-Long. For larger nonelectrolyte molecules equation (1) of the modifited McDevit-Long. theory (IV) gives results in better agreement with the experiment than those of (I), (II) and (III).