自动电位滴定法精密测定硝酸钍溶液中的钍

Accurate and Precise Determination of Thorium in Thorium Nitrate Solution by Automatic Potentiometric Titration

采用氧化还原电对Fe(Ⅲ)/Fe(Ⅱ)指示滴定终点,建立了钍的精密络合滴定方法。对影响测量的主要因素:自动滴定仪的滴定体积的重现性、酸度、滴定剂EDTA浓度、缓冲液加入量、Fe(Ⅲ)用量等进行了研究,确定了最佳测量条件。建立了以电位指示滴定终点的钍的精密测定方法。结果表明,钍取样量为5mg时,相对标准偏差达到了0.1%(n=6)。

The conventional method for determination of thorium is established by EDTA complexometric titration in which xylenol orange is used to indicate the titration end point.This paper presents a novel technique to identify the complexometric titration end point.The technique is that Fe（Ⅲ）/Fe（Ⅱ） redox couple replaces the use of xylenol orange to detect the end point by potentiometry.Various factors possibly influencing the measurement of thorium by EDTA complexometric titration were studied,such as repeatability of titrated volume,pH value,the concentration of EDTA,buffer solution and so on.The optimum conditions for the determination of thorium by EDTA complexometric titration were obtained.A new methodology was established for precise and accurate determination of thorium with Fe（Ⅲ）/Fe（Ⅱ） detecting the titration end point by potentiometry.Under optimized conditions,5 mg thorium can be determined precisely with a relative standard deviation of 0.1％（n=6）.