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本文报道了用EDTA标准溶液交流示波极谱滴定钍的方法.由于EDTA和钍离子均为交流示波极谱非电活性物种,因此加入0.3毫升的电活性铋离子作为指示离子.铋可以在其dE/dt=f(E)曲线上产生锐敏的切口,根据Th-EDTA和Bi-EDTA络合物稳定性的差别,在pH=3的醋酸缓冲液中,钍首先被EDTA完全滴定,并借助于dE/dt=f(E)曲线上Bi—EDTA小切口的出现或Bi~(3+)切口的消失来指示滴定的终点.用EDTA毫克当量数净值来计算试样中ThO_2的毫克数.有5倍量的Ca~(2+)、Sr~(2+)、Ba~(2+)、Mg~(2+);2倍量的Co~(2+)、Ni~(2+),等量的Al~(3+),0.5倍量的Mn~(2+)、混合稀土、Ce~(4+)、Zr~(4+)以及少量的Fe~(3+),均分别不干扰钍的滴定.本方法用含有毫克量钍的合成试样进行试验,前处理步骤要比文献中列举过的步骤有所简化,其准确度也高于通常的指示剂视滴定法.在测定25～80毫克ThO_2/1克合成试样时,其变动系数不超过0.92％.预计本方法可适用于测定ThO_2含量为x％范围的矿样和其他试样.
In this paper, a method for the titration of thorium by AC oscillopolarography with EDTA standard solution is reported. Since both EDTA and thorium ions are AC oscillopolarographic non-electroactive species, 0.3 ml of electroactive bismuth ions are added as indicator ions. According to the difference in stability of Th-EDTA and Bi-EDTA complexes, thorium was first completely titrated with EDTA in pH = 3 acetate buffer and the titration was performed on dE / dt = f (E) The endpoint of the titration is indicated by means of the presence of a small Bi-EDTA cut on the dE / dt = f (E) curve or the disappearance of the Bi3 + cut. The milligrams of ThO2 in the sample are calculated using the net number of milligrams of EDTA equivalent . There are five times of Ca2 +, Sr2 +, Ba2 +, Mg2 +, two times of Co2 +, Ni2 + ), The same amount of Al ~ (3 +), 0.5 times the amount of Mn ~ (2+), mixed rare earth, Ce ~ (4 +), Zr ~ (4+) and a small amount of Fe ~ Respectively, does not interfere with the titration of thorium.This method with a sample of thorium containing the amount of milligrams tested, the pretreatment steps than the literature has been simplified steps, the accuracy is higher than the usual indicator titrimetric method. In the determination of 25 ~ 80 mg ThO 2/1 g synthetic samples, the coefficient of variation of not more than 0.92%. Method is applicable to determination of ThO_2 content of ore and other samples of the range of x%.