Measurement of liquid/liquid interfacial kinetics by directly probing the concentration profiles at expanding droplets
Measurement of liquid/liquid interfacial kinetics by directly probing the concentration profiles at expanding droplets
复制标题
通过直接探测膨胀液滴的浓度分布来测量液/液界面动力学
作者：
C. Slevin;P. Unwin
描述了一种新的实验方法来测量在两种不混相液体之间的界面上发生的反应动力学。该界面是通过将给料液以缓慢的速度流过细毛细管尖端而形成的，因此液滴在第二受体相中以确定的方式周期性地形成和生长（类似于滴汞电极）。从界面延伸的产物或反应物的浓度分布在位于液滴膨胀的毛细管正下方的微电极上进行探测。通过研究三苯基氯甲烷在1,2-二氯乙烷/水界面上的水解来说明这种方法。反应速率是通过在靠近界面的水相的Ag/AgCl电极上电位测量氯离子的浓度分布来确定的。通过模拟实验几何中的质量传递，表明该反应在三苯基氯甲烷中为一级反应，反应速率常数为6.5 × 10 -5 cm s -1。
A new experimental approach for measuring the kinetics of reactions that occur at the interface between two immiscible liquids is described. The interface is created by flowing a feeder liquid through a fine capillary tip at a slow rate, so that droplets form and grow periodically in a second receptor phase in a defined way (analogous to the dropping mercury electrode). The concentration profile of either a product or reactant extending from the interface is probed at a microelectrode positioned directly below the capillary from which the droplet expands. The approach is illustrated through studies of the hydrolysis of triphenylmethyl chloride at the 1,2-dichloroethane/water interface. The reaction rate is determined by measuring the concentration profile for chloride ions potentiometrically at a Ag/AgCl electrode in the aqueous phase adjacent to the interface. By modeling mass transport in the experimental geometry, it is shown that the reaction is first order in triphenylmethyl chloride and occurs heterogeneously with a rate constant of 6.5 x 10 -5 cm s -1 .