Determination of the effective hydrodynamic radii of small molecules by viscometry.
Determination of the effective hydrodynamic radii of small molecules by viscometry.
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DOI：
10.1085/jgp.44.6.1189
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发表时间：
1961-07
期刊：
影响因子：
--
通讯作者：
SOLOMON AK
中科院分区：
文献类型：
--
作者：
SCHULTZ SG;SOLOMON AK
利用爱因斯坦的经典粘度理论确定了稀水溶液中不带电小分子的有效流体动力学半径。这样得到的半径是一个假想球体的半径，它的流体动力学行为与溶质分子加上水化水的流体动力学行为相同，水化水的结合太牢固，不能参与粘性剪切过程。所获得的结果比较有利的半径从分子模型根据原子尺寸编译鲍林。尽管将爱因斯坦理论应用于大小与水相当的分子是一个相当大的外推，但结果表明，在所研究的分子中，这种偏离理论假设的情况具有二阶重要性。利用粘滞半径，我们对斯托克斯-爱因斯坦扩散方程进行了经验修正。这种修正在形式上类似于坎宁安（22）和密立根（21）先前提出的修正，当溶质分子的大小与周围介质的不连续性相当时，这种修正特别重要。一些小的有机分子的分子半径的修正斯托克斯-爱因斯坦方程得到的装置不显着不同的半径从这些化合物的分子模型。
The effective hydrodynamic radii of small uncharged molecules in dilute aqueous solution were determined using Einstein's classical theory of viscosity. The radii thus obtained are those of a hypothetical sphere whose hydrodynamic behavior is the same as that of the solute molecule plus that water of hydration which is too firmly bound to partake in the viscous shearing process. The results obtained compare favorably with radii determined from molecular models constructed in accordance with atomic dimensions compiled by Pauling. Although the application of the Einstein theory to molecules whose size is comparable to that of water represents a considerable extrapolation, the results suggest that this deviation from the assumptions of the theory, in the case of the molecules studied, is of second order importance. Employing the viscometric radii, we have formulated an empirical correction of the Stokes-Einstein diffusion equation. This correction is similar in form to those previously proposed by Cunningham (22) and Millikan (21) and is of particular significance when the solute molecule is comparable in size to the discontinuities of the surrounding medium. The molecular radii of a number of small organic molecules obtained by means of the corrected Stokes-Einstein equation do not differ significantly from the radii obtained from molecular models of these compounds.