In 1893, Otto Wiener developed the first optical method for measuring the rate at which two liquids mix by interdiffusion. His elegant experiment is often reproduced at University to illustrate the phenomenon of molecular diffusion. It is based on the property that an interface between two liquids deflects light by refraction because of the composition gradient formed by interdiffusion. In this study, we refine the analysis that is generally made of Wiener's experiment by performing both simulations of the interdiffusion and ray tracing in the tank that contains the two liquids. By considering first the water/glycerol model system, we determine the time interval during which it is possible to simply extract the value of the interdiffusion coefficient. Then, we extend this study to alcohol/water systems for which unfamiliar experimental patterns are obtained. These images are explained qualitatively by modeling the two main ingredients responsible for their formation, namely, how the interdiffusion coefficient and the refractive index depend on the composition.

中文翻译：

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用维纳光学方法研究液体中的分子扩散

1893 年，奥托·维纳 (Otto Wiener) 开发了第一种通过相互扩散测量两种液体混合速率的光学方法。他优雅的实验经常在大学被复制来说明分子扩散的现象。它基于以下特性：由于相互扩散形成的成分梯度，两种液体之间的界面通过折射使光发生偏转。在这项研究中，我们通过对包含两种液体的罐中的相互扩散和光线追踪进行模拟，来完善通常由 Wiener 实验构成的分析。通过首先考虑水/甘油模型系统，我们确定可以简单地提取互扩散系数值的时间间隔。然后，我们将这项研究扩展到获得了不熟悉的实验模式的酒精/水系统。这些图像通过对导致它们形成的两个主要成分进行建模来定性地解释，即相互扩散系数和折射率如何取决于成分。