【摘要】 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Bi³⁺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ThO₂的毫克数.有5倍量的Ca²⁺、Sr²⁺、Ba²⁺、Mg²⁺;2倍量的Co²⁺、Ni²⁺,等量的Al³⁺,0.5倍量的Mn²⁺、混合稀土、Ce⁴⁺、Zr⁴⁺以及少量的Fe³⁺,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ThO₂/1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ThO₂含量为x％范围的矿样和其他试样.更多还原

【Abstract】 This paper reports a method for A. C. oscillopolarographic titration of thorium with standard EDTA solution.. Both EDTA and thorium ion are A. C. oscillopolarographic electroinactive species, so O.Sml (0.02M) of electroactive bismuth ion Bi3+ solution is added as indicating ion which givesa sharp incision on its curve. According to the difference of stabil-ity of Th-EDTA and Bi-EDTA complexes in an acetic buffer solution with pH = 3, thorium ion can be first completely titrated with titrant EDTA and resort to the appearance of Bi-EDTA Small incision or desappearance ofBi3+ incision on its curve to indicate the end point of titration.The net number of gram-milliequivalents of EDTA is used to calculate milligrams of Th02 in the sample.In spite of the presence of 5 times quantities of Ca2 + ,Sr2+,Ba2+ ,Mg2+ ,2 times Co2+ ,Ni2+ 1.5 times A13+,0.5 times Mn2+ , Fe3+ , and the mixture of rare earth elements, Ce4+ , Zr4+ respectively, the determination of thorium is not interfered. The proposed method may be used to determine milligrams of thorium oxide in synthetic sample. The procedure of pretreatment of sample is simpler than the procedure listed in literatures and the accuracy of the adopted method is also superier to its ordinary visual complexmetric titration. In determination of 25~80 mg Th02/1g synthetic sample, the coefficient variation is less than 0.92% .This method is supposed to be suitable for determining thorium ores and other thorium samples which contain X% Th02. Southern China Institute of Technology更多还原