交流ポーラログラフ法による鉄鋼中のガリウム定量法

概要

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A new method for the a. c. polarographic determination of gallium using perchloric acidammonium thiocyanate as supporting electrolyte solution was studied and applied to iron and steel. The procedure is as follows. One g. sample is decomposed with the mixture of nitric and hydrochloric acids, and evaporated to white fume after adding perchloric acid. After reducing ferric ions with 1-ascorbic acid, gallium is extracted with MIBK from hydrochloric acid solution and back-extracted with water. This treatment is repeated once more, and water is removed by moderate evaporation. Perchloric acid (60%) 0.3ml and ammonium thiocyanate solution (50.0%) 5.0 ml are added and diluted with water to exact 25 ml. The oxygen dissolved in an aliquot is removed completely by passing nitrogen gas. This solution is applied to an a. c. polarography under the voltage between -0.55 and -0.85V against mercury pool and the amount of gallium is determined from the wave height of -0.75V. This method is carried out within an absolute error of 0.005%. The time required for an analysis is about 90 min. The 38 elements coexisting commonly in iron and steel scarcely interfere.
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