| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1992: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1991: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
A spectrophotometric method has been established for the determination of each sulfur species of sulfide, sulfite, thiosulfate, trithionate and tetrathionate in mixtures.
The proposed method comprises the following five procedures. In Procedure I for the determination of sulfide, the thiocyanate formed from the hydrogen sulfide evolved from the mixtures was measured using iron(III).In Procedure II for the determination of sulfite and in Procedure III for thiosulfate, excess iodine from its reactions with the sulfur dioxide separated in Procedure II and the thiosulfate in the mixtures from which both sulfide and sulfite were purged in Procedure III, was measured. In Procedure IV for total amounts of thiosulfate and tetrathionate, excess iodine for both the thiosulfate in the mixtures and the thiosulfate formed from tetrathionate by its sulfitolysis was measured. In procedure V for total amounts of thiosulfate, trithionate and tetrationate, all these three species were oxidized to sulfate by iodate in a strong acid medium and the iodine, formed from excess of the iodate by the addition of iodide, was measured as triiodide. These three sulfur compounds in the mixtures give the following equivalents in Procedures IV and V : Procedure IV=S_2O_3^<2->+S_4O_6^<2-> and Procedure V=S_2O_3^<2->+S_3O_6^<2->+7/S_4O_6^<2->. Hence, the following equations can be obtained:[S_3O_6^<2->]=1/(3III-7IV+4V) and [S_4O_6^<2->] = IV-III. Here, III, IV and V denote the molar concentrations of thiosulfate determined by Procedure III, IV and V, respectively. Good recoveries of the above-mentioned five sulfur species added to hot-spring and lake water samples were achieved using the proposed method.
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