電位差滴定法によるステンレス鋼着色液中の遊離硫酸の定量

概要

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A rapid potentiometric titration mothod of free sulfuric acid in the colouring solution for stainless steels is described. The solution was composed of chromic acid (CrO_3, 250 g/l), sulfuric acid (H_2SO_4, 500 g/l) and metallic sulfate ions as Fe_2(SO_4)_3, Cr_2(SO_4)_3 etc. For the control of the tints and qualities of coloured films, the determination of free sulfuric acid was needed. But the conventional procedures could not be employed because of co-precipitation of both sulfuric acid and metallic sulfate as BaSO_4. It was found the following procedure was effective to take away the interference of the metallic sulfate ions. (1) At first, total [H^+] at 1st titration end point of H_2SO_4 and H_2Cr_2O_7 in the sample solution was determined with potentiometric titration method after addition of Zn-EDTA for masking metallic ions. (2) Free sulfuric acid concentration was determined after subtraction of [H^+]_<CrO_3> of 1st dissociation of CrO_3 from total [H], which was determined by the another chemical analysis of Cr(VI). The time required for this method was about 30 minutes for one sample and the results were accurate and reproducible.
社団法人日本鉄鋼協会の論文
1989-01-01