库仑滴定法测定水杨酸醇溶液中水杨酸的含量

Determination of salicylic acid in salicylic acid alcoholic solution by coulometric titration

目的：建立库仑滴定法测定水杨酸的含量。方法：以恒电流电解0．5mol·L^-1溴化钾溶液～1．0mol·L^-1冰醋酸溶液（1：1），采用电流上升法确定终点，根据法拉第定律计算水杨酸的含量。结果：水杨酸在0．8340～2．502mg·ml^-1范围内与电量呈良好的线性关系（r=0．9997），平均回收率99．70％（RSD=0．78％），同批次水杨酸醇溶液用库仑滴定法和氢氧化钠滴定法测定含量，含量平均值间的相对平均偏差为0．10％。结论：采用库仑滴定法和氢氧化钠滴定法测定同批次水杨酸醇溶液的含量结果一致。所建立的方法简单、准确、重复性好，被测成分微量，还具有不需要配制和标定滴定液的优点，可用于水杨酸醇溶液的质量控制。

OBJECTIVE To establish coulometric titration method for determination of saIicylic acid. METHODS The electrolyte of 0. 5 mol.L^-1 KBr and 1.0 mol.L^-1 CHdCOOH（1 ： 1）were electrolized by constant current. The end point was determined by the sudden rising current. The content of the salicylic acid was determined according to Faraday＇s laws. RESULTS The consumed quantity of electricity was in line with the concentration of the salicylic acid （r = 0. 999 7） at the range of 0. 834 0 - 2. 502 mg.ml^-1. The average recovery rate of salicylic acid was 99. 70% （RSD= 0. 78%）. For the same batch of salicylic acid alcoholic solution, the relative average deviations of average contents determined by coulometric titration and sodium hydroxide titration method was 0. 10%. CONCLUSION Compared with the traditional sodium hydroxide titration method, the newly established coulometric titration method could achieve the same results. The characteristics of the established method are simple, accurate, with good reproducibility, and can be used for the determination of trace sample. In addition this method does not need to prepare and calibrate the titration solution. This method can be used to control the quality of salicylic acid.