This disc uses the Standard Method DPD procedure to indicate efficiency of chlorine application in water and wastewater treatment plants, as well as in pollution control. Permanent non-fading glass colour standard is featured. Intended use with No. 673-700-11 Hellige Pocket Comparator and Standard Colour Comparator. Price for each Disc includes 50 DPD No. 1 tablets, 50 DPD No. 3 tablets and plastic stirring rod.
DPD No. 1 tablets are for free available chlorine only. When DPD No. 3 tablets are used with No. 1 tablets, an increase in colour represents monochloramine form of chlorine.