SEPARATION AND SPECTROPHOTOMETRIC DETERMINATION OF THIOSULFATE, SULFITE AND SULFIDE IN THEIR MIXTURES

The conditions under which each species of thiosulfate, sulfite and sulfide can be selectively separated from their mixtures have been established. The proposed method comprises three procedures: excess iodine for its reaction with the thiosulfate separated in Procedure I and the thiosulfate formed from sulfur dioxide in Procedure II; the thiocyanate formed from hydrogen sulfide in Procedure III is spectrophotometrically measured. The sulfur dioxide separated from a mixture of thiosulfate and sulfide was introduced into a solution containing a buffer and sulfur; the sulfur dioxide was completely converted into thiosulfate. Procedure I can be applied to the determination of up to 4.8 X 10(-4) M thiosulfate in the presence of sulfite and sulfide, Procedure II up to 4.8 X 10(-4) M sulfite in the presence of thiosulfate and sulfide, and Procedure III up to 6X10(-4) M sulfide in the presence of thiosulfate and sutfite. Good recoveries of thiosulfate, sulfite and sulfide from hot-spring and lake-water samples were achieved using the proposed method.