Spectrophotometric Determination of Thiosulfate by Its Reaction with Silver(I) and Solvent Extraction of Excess Silver(I) with Methylene Blue

摘要

For reaction with thiosulfate, excess silver(I) was extracted as an ion-pair of dicyanoargentate(I) with Methylene Blue; the extract was measured spectrophotometrically at 657nm for the determination of thiosulfate. The conditions for thiosulfate to be stoichiometrically converted into silver sulfide were established by varying the pH and reaction time. A linear calibration graph with a negative slope was obtained over the 5.4×10-8-4.5×10-6M (0.006-0.504ppm) thiosulfate. The relative standard deviation was 0.79% at the 2.5×10-6M thiosulfate level. The effective molar desorptivity for thiosulfate at 657nm is -1.99×105l mol-1 cm-1. The proposed method has been successfully applied to the determination of thiosulfate in hot-spring water containing chloride.