With FAS-DPD Titration you can read free and combined chlorine directly, without subtraction, measure levels in increments as low as 0.2 ppm, and eliminate color matching.
Free & total chlorine, .5-5 ppm, bromine 1-10 ppm, pH 7.0-8.0, acid and base demand, total alkalinity, calcium hardness cyanuric acid. Uses 9058 comparator. Sanitizer tests are titrations to improve accuracy and eliminate color-matching problems and free and combined chlorine 1 drop = 0.2 or 0.5 ppm. .75 oz bottles. Sold each.