SPECTROPHOTORNETRIC METHOD FOR THE DETERMINATION OF SULPHTING AGENTS an‎d COMPREHENSIVE STUDY OF THE STOICHIOMETRY OF THE REAGENTS EMPLOYED

This work includes, two parts, the first part is simple, not time consuming and rapid spectrophotometricmethod for the determination of sulphiting agents (sulphur dioxide, metabisulphite, sulphite). Based ontheir reaction with phosphomolybdate (ammonium molybdate and phosphate) in sulphuric acid medium inthe presence of hydroquinone. The calibration graph was found to be linear over the concentration range8.076-53.84 mg ml^-1 as sulphur dioxide. The molar absorbitivity and Sandell sensitivity of the system at 732 nm were 0.751 × 10^3 l mol^-1 cm^-1 and 0.139 (mu)g cm^-1 respectively. The relative standard deviation(RSD%) was calculated to be less than 1.5%, whereas, the relative error was varied between -2.86 and 3.24%. The method was applied for the determination of sulphur dioxide in dried grape sample. The second part includes study of stoichiomerty of the reactants in this system comprehensively under the recommended optimum conditions and also at Keggin structure composition.