SPECTROPHOTOMETRIC REACTION-RATE METHOD FOR THE DETERMINATION OF SULFIDE BY CATALYTIC ACTION ON THE OXIDATION OF SODIUM-AZIDE BY IODINE

A catalytic kinetic method has been used for the determination of ultr a trace amounts of total dissolved sulfide based on its catalytic effe ct on the reaction between sodium azide and iodine in aqueous solution . Sulfide over the range of 0.020-0.500 mu g.ml(-1) was determined spe ctrophotometrically by measuring the decrease in absorbance of iodine at 348 nm by the fixed-time method. The decrease in absorbance during the first 0.5-3.0 min from initiation of the reaction is related to th e concentration of sulfide. The detection limit is 0.010 mu g.ml(-1). The relative standard deviation for the determination of 0.050 mu g.ml -1 of sulfide was 2.2%. The proposed method was successfully applied f or the determination of sulfide in synthetic samples, spring water and of sulfur in steel.