Double indication in catalytic-kinetic analysis: simultaneous photometric and thermometric indication of the iodine-azide reaction in closed and flow systems

Abstract The iodine—azide reaction catalyzed by sulphur-containing compounds is followed simultaneously by optical and thermometric measurements in closed and flowing systems. In the closed system, thiosulphate can be determined in the range 32.4–324 μg ml -1 , by observing the turbidity caused by the nitrogen formed during the reaction and the temperature changes. With the flow apparatus, thiosulphate can be determined in the range 112–1120 μg ml -1 by continuously mixing the sample and reagent solutions. H 2 S in nitrogen 5–100 ppm) is measured by sweeping the gas into the reaction Cuvette. In a third flow procedure, H 2 S is liberated continuously from sodium sulphide solutions (0.1–10 μg S 2- ml -1 ) by ascorbic acid, and swept to the measuring cuvette with nitrogen.