界面移动法测定离子迁移数实验的改进

Improvement for Measuring Transference Numbers of Ions by Moving-Boundary Method

对界面移动法实验装置进行了数字化改造,采用电导率-时间曲线测量方法,准确、客观地确定溶液界面在两对电导电极间的移动速率。该方法消除了人工观测的主观偏差,且无需使用指示剂标示界面,解决了低浓度条件下界面无法观察的问题,并可将实验测定对象由传统的酸性电解质溶液(如HCl水溶液)扩展到中性电解质溶液(如NaCl、KCl等)。该方法在实验浓度范围内(约0.01–0.1mol·L^(-1))测定的氢离子迁移数值在合理偏差的区间内(0.8230–0.8350),可用于测定电解质的离子迁移数和电迁移率等性质,为物理化学实验教学提供一种新方法。

The apparatus for moving-boundary method is upgraded by digital technique.The conductivity-time curve is measured,and the moving velocity of the boundary through two pairs of conductive electrodes can be determined precisely and objectively.This method eliminates the subjective deviation from manual observation.No indicator is needed to mark the boundary,and the problem of unobservable boundary at low concentration is therefore solved.The experimental object is also extended from traditional acidic electrolyte solution(e.g.,aqueous HCl)to neutral electrolyte solution(e.g.,aqueous NaCl,KCl,etc.).In the range of experimental concentrations(approx.0.01 mol∙L^(−1) to 0.1 mol∙L^(−1)),the transference number of H+can be obtained with a reasonable deviation(0.8230–0.8350)by this method.The improved apparatus can be used to determine the transference numbers and mobilities of electrolytes,which provides a new way for physical chemistry experiment teaching.