The loss of stability of the horizontal interface in a two-layer system of immiscible liquids with a diffusing component was investigated experimentally. To this end, the evolution of the system, which was based on a mixture of chlorobenzene and benzene (lower layer) and water or an aqueous solution of sodium chloride (upper layer) was examined. At the beginning of the experiment, the diffusing component (acetic acid), which was a surface-active substance (surfactant), was located in the lower layer of the system. Since the initial densities of the base fluids were close to or equal to the acid density, all further density changes in the system were only the result of the contraction effect. The prepared liquids filled the vertical Hele-Shaw cell and were separated by a movable partition. The removal of the partition led to the development of the diffusion process of acid, which turned to be the reason for the loss of stability of the system provoking the deformation of the inter-phase boundary and the detachment of droplets from it. The dependences of changes in density and interfacial tension at the point of maximum deflection of the boundary on time and initial acid concentration in the lower layer were determined. For case of discontinuity of the interfacial surface a neutral curve was obtained. The analysis of the system behavior revealed a stabilizing role of the solutal Marangoni convection.

中文翻译：

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在不混溶液体系统中由于表面活性剂扩散而引起的界面不稳定性

实验研究了具有扩散成分的两层不混溶液体系统中水平界面稳定性的损失。为此，检查了基于氯苯和苯（下层）和水或氯化钠水溶液（上层）的混合物的系统演变。在实验开始时，扩散成分（乙酸）是一种表面活性物质（表面活性剂），位于系统的下层。由于基础流体的初始密度接近或等于酸密度，因此系统中所有进一步的密度变化仅是收缩作用的结果。所制备的液体充满了垂直的Hele-Shaw池，并由可移动的隔板隔开。分隔物的去除导致了酸的扩散过程的发展，这成为系统失去稳定性而引起相间边界变形和液滴从其分离的原因。确定了在边界的最大挠度点处密度和界面张力的变化与时间和下层中初始酸浓度的关系。对于界面不连续的情况，获得了中性曲线。对系统行为的分析表明，Marangoni对流具有稳定作用。确定了在边界的最大挠度点处密度和界面张力的变化与时间和下层中初始酸浓度的关系。对于界面不连续的情况，获得了中性曲线。对系统行为的分析表明，Marangoni对流具有稳定作用。确定了在边界的最大挠度点处密度和界面张力的变化与时间和下层中初始酸浓度的关系。对于界面不连续的情况，获得了中性曲线。对系统行为的分析表明，Marangoni对流具有稳定作用。