filtre indicateur imprégné

CONT: Impregnated filters. These methods use the reaction of SO[subscript 2] with a basic compound which can then be measured colorimetrically. Generally samples are gathered on filters which have been impregnated with a solution such as potassium carbonate which reacts with SO[subscript 2]. The sulfite salt is oxidized to SO[subscript 4] with hydrogen peroxide and is reacted with a barium-thorin complex to provide a coloured solution of the liberated thorin whose absorbance is proportional to the SO[subscript 2] content.