引用本文:
姬泓巍, 谢文蕙. 邻、间、对位-二甲苯在盐的水溶液中活度系数的研究[J]. 物理化学学报,
1987, 3(02): 146-154.
doi:
10.3866/PKU.WHXB19870208
Citation: Ji Hongwei, Xie Wenhui. STUDIES ON ACTIVITY COEFFICIENTS OF o,m,p-XYLENE IN AQUEOUS SALT SOLUTIONS[J]. Acta Physico-Chimica Sinica, 1987, 3(02): 146-154. doi: 10.3866/PKU.WHXB19870208
Citation: Ji Hongwei, Xie Wenhui. STUDIES ON ACTIVITY COEFFICIENTS OF o,m,p-XYLENE IN AQUEOUS SALT SOLUTIONS[J]. Acta Physico-Chimica Sinica, 1987, 3(02): 146-154. doi: 10.3866/PKU.WHXB19870208
邻、间、对位-二甲苯在盐的水溶液中活度系数的研究
摘要:
本文用紫外分光光度计测定了25 ℃下邻、间、对位三种二甲苯在八种盐水溶液中的活度系数f和盐析常数k值。所用的盐为LiCl、NaCl、KCl、SrCl2、BaCl2、LiBr、NaBr、KBr。将三种二甲苯的lgf分别对八种盐的浓度C_s作图, 得到二十四条通过原点的直线, 符合Setschenow盐析经验公式。三种二甲苯的盐析次序均为BaCl2>SrCl_2>NaCl>KCl>NaBr≈LiCl>KBr>LiBr.
实验表明: 每种盐的盐效应是单个离子的贡献之和; 随着二甲苯偶极矩的增大, 盐析常数有下降的趋势。
本文计算了四种理论的盐析常数k_s值。对内压力理论改进公式提出了一些假设, 选用了Latimer离子半径进行具体计算, 结果与实验值符合得较好.
对于体积较大的非电解质, 虽然静电力起主要作用, 但必须考虑色散力对盐析常数的影响。本文再一次证实和支持了黄子卿提出的盐效应机构。
实验表明: 每种盐的盐效应是单个离子的贡献之和; 随着二甲苯偶极矩的增大, 盐析常数有下降的趋势。
本文计算了四种理论的盐析常数k_s值。对内压力理论改进公式提出了一些假设, 选用了Latimer离子半径进行具体计算, 结果与实验值符合得较好.
对于体积较大的非电解质, 虽然静电力起主要作用, 但必须考虑色散力对盐析常数的影响。本文再一次证实和支持了黄子卿提出的盐效应机构。
English
STUDIES ON ACTIVITY COEFFICIENTS OF o,m,p-XYLENE IN AQUEOUS SALT SOLUTIONS
Abstract:
The solubilities of o, m, p-xylene in water as well as in the aqueous salt solution were determined at 25 ℃ by spectrophotometer. The activity coefficient (f) of each of the xylenes has also been calculated. The salts used are LiCl, NaCl, KCl, SrCl_2, BaCl_2, LiBr, NaBr and KBr.
The salt concentrations (c_s) used are 0-1 mol L~(-1). When logf were ploted vs. c_s for eight salts, the obtained results are all straight lines. On comparison of the slopes of these 24 lines, the salting-out order is BaCl_2>SrCl_2>NaCl>KCl>NaBr≈LiCl>KBr>LiBr for each of the xylenes.
The salt effect constant k_s can be expressed in terms of the sum of k_+ and k_-. The values of k_ decreases with the increase of the dipole moment of the xylene molecule.
The salting-out constants of these xylenes in eight aqueous salt solutions have been calculated respectively by the formulas of (1) Debye-McAulay, (2) Conway-Desnoyers-Smith, (3) McDevit-Long and (4) modified internal pressure theory.
Some assumtions were made for the modified equation of the internal pressure theory. When the distance between ion and nonelectrolyte molecule in aqueous salt solution was calculated, Latimer′s radii are used instead of the Pauling′s radii of ions. For larger nonelectrolyte molecules, equation of the modified internal pressure theory (4) given results in better agreement with the experiment than those of (1), (2) and (3).
The salt concentrations (c_s) used are 0-1 mol L~(-1). When logf were ploted vs. c_s for eight salts, the obtained results are all straight lines. On comparison of the slopes of these 24 lines, the salting-out order is BaCl_2>SrCl_2>NaCl>KCl>NaBr≈LiCl>KBr>LiBr for each of the xylenes.
The salt effect constant k_s can be expressed in terms of the sum of k_+ and k_-. The values of k_ decreases with the increase of the dipole moment of the xylene molecule.
The salting-out constants of these xylenes in eight aqueous salt solutions have been calculated respectively by the formulas of (1) Debye-McAulay, (2) Conway-Desnoyers-Smith, (3) McDevit-Long and (4) modified internal pressure theory.
Some assumtions were made for the modified equation of the internal pressure theory. When the distance between ion and nonelectrolyte molecule in aqueous salt solution was calculated, Latimer′s radii are used instead of the Pauling′s radii of ions. For larger nonelectrolyte molecules, equation of the modified internal pressure theory (4) given results in better agreement with the experiment than those of (1), (2) and (3).
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