双指示剂法测定混合碱实验的改进

Improvement of Double Indicator Method for Determination of Mixed Alkali

基于酚酞和甲基橙的双指示剂法测定混合碱是高校本科实验化学课程的一个重要实验,然而第一终点颜色由红色变为近无色,不易观察和控制,从而导致测定结果偏差交大。本实验将蓝蝴蝶鸢尾提取液作为辅助指示剂,对基于酚酞和甲基橙传统双指示剂测定混合碱的方法进行了改进,提高了第一终点的准确度且不影响第二计量点的判断。该研究方法兼顾实用性和趣味性,为混合碱的测定提供了重要参考。

The determination of mixed alkali by double indicator method based on phenolphthalein and methyl orange is an important experiment in the undergraduate experimental chemistry course in colleges and universities.However,the color of the first end point changes from red to nearly colorless,which is not easy to observe and control,resulting in large deviation of the determination results.In this experiment,using the extract of Iris iridis as an auxiliary indicator,the traditional double indicator method based on phenolphthalein and methyl orange for the determination of mixed base was improved,which improved the accuracy of the first end point and did not affect the judgment of the second metering point.The research method is practical and interesting,and provides an important reference for the determination of mixed alkali.