同位体希釈・スパークイオン源質量分析法によるフェロアロイ，鉄鉱石，銑鉄中の硫黄定量

抄録

The determination of sulfur in ferroalloy, iron ore and pig iron by the isotope dilution method using ³⁴S enriched sulfur, combined with spark source mass spectrometry, was studied. This method is based on a conventional gravimetric method. Samples are dissolved in nitric acid and hydrochloric acid containing potassium chlorate and the spike solution which is prepared by dissolving elemental ³⁴S in nitric acid, and potassium chlorate is added to the solution. In ferrosilicon and high carbon ferrochrome samples, those are fused with sodium carbonate or sodium carbonate and sodium peroxide. The resulting solution is evaporated to drynass. The salts are dissolved in hydrochloric acid, and metallic zinc is added to reduce ferric ions to ferrous ions. Barium chloride is added to the solution to precipitate sulfur as barium sulfate, and then the precipitate is filtered and ignited. The ignited residue is mixed with graphite powder and pressed into electrodes.
The method was applied to the determination of sulfur in the JSS, NBS and BCS standard samples, and the results with satisfactory precision and accuracy were obtained for the analyzed samples except for ferrosilicon samples. The poor precision for ferrosilicon sample seems to be due to the blank of sulfur from reagents (Na₂O₂, etc.) used.