For determination of chloride, the pH of the sample is adjusted to approximately pH 3 with the nitric acid reagent, turning the solution yellow. The mercuric ions present in the titrant react with chloride in the sample. Once all of the chloride is in the mercuric chloride form, excess mercuric ions are present, forming a purple complex with the diphenylcarbazone indicator. The number of milliliters of titrant used to change the solution’s color from yellow to purple will determine the chloride concentration in mg/L (ppm). These reagents are designed to be used with samples that have an expected chloride range of 0 to 100 mg/L (ppm) and 0 to 1000 mg/L (ppm).