A SPECTROPHOTOMETRIC REACTION RATE METHOD FOR DETERMINATION OF BISMUTH USING A DIMERIC HETEROPOLYMOLYBDATE

A new method for the determination of bismuth(III) is described based on the initial rate of formation of the reduced dimeric heteropolymolybdate, 18-molybdobismuthophosphoric acid, from the reaction between phosphate, bismuth, molybdate, and ascorbic acid. The relative precision for the analysis of 4 ppm bismuth was better than 0.5% and of 0.04 ppm bismuth, the lower concentration limit, better than 10%. The formation of the reduced 18-molybdobismuthophosphoric acid is accomplished under conditions where 12-molybdophosphoric acid does not reduce. The method is simple and rapid, requiring only 20-60 seconds of reaction time. A study of diverse ions is presented and advantages of the rate method are discussed. © 1969, American Chemical Society. All rights reserved.