クロム(III)及び酒石酸イオン共存下のおける亜鉛(II)イオンのEDTAによる電導度滴定

概要

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Conductometric titration of Zn(II) ion with EDTA in the presence of Cr(III) and tartrate ions was investigated. Although Zn(II) ion forms partially the ternary complex, Zn-Cr-tartrate, with Cr(III) and tartrate ions, the determination of Zn(II) ion is possible without interference with the complex formation. Recommended procedure is as follows: The sample solution of Zn(II) ion containing up to 30mg of Cr(III) and 360mg of tartrate ions is transferred into a 200ml beaker. After adding 2ml of 3M acetate buffer solution (pH 5.5), the solution is diluted to 120ml with water and titrated with 0.1M EDTA solution at a rate for 0.30ml per min. The change of conductance is recorded. On the titration curve, two inflection points are always obtained, because of the partial ternary complex formation. Total Zn(II) ion in the solution is determined from the second inflection point. The proposed method allows (6〜20)mg of Zn(II) ion to be determined satisfactorily with the coefficient of variation of less than 0.4%. The first inflection point corresponds to Zn(II) ion which does not form the ternary complex. This method is applied also to the study on the ternary complex formation under various conditions.
社団法人日本分析化学会の論文
1978-12-05