Rapid determination of sulfite ion by using detector tubes

A rapid and simple method for the determination of sulfite ion in water was investigated. The detector reagent was prepared as follows: cellulose powder that was impregnated with 0.2 % Na-CMC(sodium salt of carboxymethyl cellulose) was soaked in a mixed solution of 0.05 % Malachite Green-Magdalarot. After 10 min. the colored cellulose powder was filtered by suction and dried at 100 °C. And then, a portion of 0.1 g of the detector reagent was filled in a glass tube (about 1.8 mm inside diameter) to a length of 11 cm, and its both ends fixed with cotton stoppers. When this detector tube was soaked in a sample solution containing sulfite ion, the color changed from bluish purple to pink corresponding to the length of discolored zone of Malachite Green. The determination of sulfite ion was possible by measuring the length of the pink zone. By this method, the sulfite ion in the range from 10 ppm to 100 ppm {(0.040.40) mg/5 ml as sulfur dioxide} was determined. The variation coefficient was 6.7 % at the sulfite level of 0.20 mg SO2/5 ml. Dithionite, sulfide, disulfate and nitrite ions interfered with the determination of sulfite ion.