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A water sample is run through an ion exchanger in which all of the cations are replaced with hydrogen ions. The sulfate is determined through titration in the presence of a previously prepared barium chloride solution, of which a known amount in excess of that required is added in advance. The quantity is measured by complexometric titration. The difference between the initial concentration of barium chloride and the amount determined by back titration corresponds to the sulfate content.

In many cases, particularly at higher contents, an alternative and sufficiently accurate measurement is possible, called the “negative m value” or the “total mineral acid value” (without carbonic acid). This is achieved through titration. Subsequently, the mval values for the anions (Cl^-, NO₃^-, NO₂^-, PO₄^3-) are subtracted from the result.

Transformation of the chloride ions in the presence of silver ions produces silver chloride, which is not very soluble, until all the chloride ions are bound. The excess silver ions react with chromate ions to silver chromate, which exhibits a reddish brown color:

Cl ^-     +   Ag⁺            →     AgCI

2 Ag⁺ +   CrO₄^2-        →    Ag₂CrO₄

Refer to W-000.40.115 Oxygen in Water, Titration Method According to WINKLER

Given the very low levels of oxygen present in boiler water, a method employing iodine comparison is recommended. In this analysis, the blank value of the reagent is measured by titrating a water sample free of Mn²⁺ (“red”).