溶媒抽出-直流ポーラログラフ法によるヒ酸の間接定量

概要

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After an addition of 1 ml of 5% ammonium molybdate to 10 ml of a solution containing up to 13 μg As as As (V) and 0.40.7N in sulfuric acid, arsenomolybdic acid formed was extracted with 10 ml of iso-butanol. A 2 ml aliquot of the extract washed four times with 5 ml of 0.5N sulfuric acid was taken into a 25 ml volumetric flask, and filled up to the mark with 1.4 ml of perchloric acid (60%), 5 ml of hydrogen peroxide (3%) and water. Arsenomolybdic acid was decomposed at once into peroxymolybdic acid in the homogeneous solution. A kinetic polarographic wave was observed with the solution. By measuring the height of the maximum wave appearing at about +0.2 V vs. S.C.E., arsenic was determined indirectly. Phosphorus was coextracted and zirconium hindered the extraction. A preliminary extraction with butylacetate of the hydrochloric acid solution was adopted to eliminate the interference from phosphorus less than 20 μg, and the recovery of arsenic was about 90% when the extraction was repeated three times. Analytical results obtained by the proposed method for arsenic in steels were in close agreement with those by the colorimetric method. The arsenomolybdic acid extracted with iso-butanol seemed to be the arseno-12 acid.
社団法人日本分析化学会の論文