物理化学学报 >> 1986, Vol. 2 >> Issue (04): 302-309.doi: 10.3866/PKU.WHXB19860407

研究论文 上一篇    下一篇

298.1 K时脂肪酸钠盐对定组成水溶液中非水组分活度系数的影响

黄忆宁; 倪朝烁; 李芝芬; 刘瑞麟   

  1. 北京大学物理化学研究所
  • 收稿日期:1985-11-22 修回日期:1986-03-24 发布日期:1986-08-15

THE EFFECT OF SALTS OF FATTY ACIDS ON THE ACTIVITY COEFFICIENT OF NONAQUEOUS COMPONENT IN AQUEOUS SOLUTIONS WITH FIXED COMPOSITION 298.1 K

Huang Yining; Ni Chaoshuo; Li Zhifen; Liu Ruilin   

  1. Institute of Physical Chemistry, Peking University
  • Received:1985-11-22 Revised:1986-03-24 Published:1986-08-15

摘要: 本文报告了298.1 K下甲酸钠(C_1), 乙酸钠(C_2)、丙酸钠(C_3)、丁酸钠(C_4)、戊酸钠(C_5)、已酸钠(C_6)和庚酸钠(C_7)七个盐对水溶液中乙醇、丙酮和乙腈三个溶质的活度系数的影响。实验方法是, 固定水溶液中乙醇、丙酮和乙腈的浓度(摩尔分数约为0.05), 用气相色谱法检测不同盐浓度下平衡气相中溶质分压的变化, 从而得出溶质的盐效应活度系数γ。
本文给出了一个可以连续取样的气液平衡装置的设计。
由实验结果可见, 不同碳链大小的脂肪酸根离子的盐效应作用差别很大。C_1、C_2的盐效应主要由于静电作用; 对C_3、C_4盐, 除静电作用外,它们的疏水基与溶质疏水基的相互作用对盐效应有显著影响; C_5、C_6和C_7的盐效应则反映了疏水离子的特色, 疏水水化、疏水相互作用、疏水离子形成的聚集体与不同官能团的特定相互作用等几项因素, 导致儿个溶质盐效应的差异。

Abstract: This paper reports the effect of seven salts, namely sodium formate (C_1), sodium acetate(C_2), sodium propionate(C_3), sodium butyrate(C_4), sodium pentanoate(C_5), sodium caproate (C_6) and sodium heptylate(C_7), on the activity coefficients of three solutes, namely ethanol, acetone and acetonitrile, in aqueous solution at 298.1 K. Adopted method is to measure the variation of partial pressure of solute in the equilibrium vapor phase with the concentration of the salt at fixed composition of aqueous solution of solute by gas chromatography, thus to calculate the salt effect activity coefficient of the nonaqueous component in solution.
A design of vapor-liquid equilibrium apparatus for sequential sampling is described in detail.
According to the experimental result, it can be considered that the mechenism of salt effect changes dramatically as the num ber of carbon in the chain of anion increases. Electrostatic in teraction contributes to salt effect mainly for C_1 and C_2 salts. In addition to electrostatic, interaction between the hydrophobic group of C_3 and C_4 anion and that of solute raises a considerable contribution to it. The salt effects for C_5, C_6 and C_7 salts characterize the hydrophobic ions that the hydrophobic hydration, the hydrophobic interaction and the special interaction between the aggregation of hydrophobic ions and the various functional group cause the differentiation of salt effect o three solutes.