The Free Chlorine powder reagent kit includes high-quality reagents that are ready-to-use with MW10 Free Chlorine Tester. The Method is an adaptation of USEPA 330.5. The reagents reaction between the DPD Free Chlorine and the reagent causes a pink tint in the sample. Simply add the reagent to the sample, wait for the reaction to take place and the photometer determines the concentration based on the color. The reagents are designed for use with samples that have an expected range of 0.00 to 2.50 ppm free chlorine.