开路电位法研究高锰酸钾滴定柠檬酸

Study on Titration of Citric Acid by Potassium Permanganate with Open Circuit Potential Method

以开路电位的方法探测了高锰酸钾滴定柠檬酸的电位变化过程。实验发现,高锰酸钾中硫酸含量为5%(体积),温度为30℃时,滴定体积偏大;50℃时滴定体积稍有误差,70℃时滴定体积偏小。若硫酸含量提高至15%(体积),则滴定体积均偏小。误差原因在于不同酸度条件下,高锰酸钾还原历程不同,5%硫酸时,以两步法还原,而15%硫酸时以一步法直接还原。

A method of open circuit potential titration for the quantitative analysis of citric acid by potassium permanganate was established. The results showed that when there was 5 % （V/V） sulphuric acid in the potassium permanganate solution, the titration volume of potassium permanganate was bigger than calculated value at 30℃, close to at 50℃ and smaller at 70℃. When sulphuric acid was increased to 15% （V/V）, both the titration volumes at 30℃ and 50℃ were smaller than calculated value. Under the condition of different acidity, there were two different reduction process for potassium permanganate, that is, two steps in 5% （V/V） sulphuric acid, and one step in 15% （V/V） sulphuric acid.