The method describes how to determine the sulfate content of water through precipitation.
Barium chloride sulfate is precipitated as coarse crystalline barium sulfate. The precipitate is determined gravimetrically:
SO42- + Ba2+ → BaSO4
This method describes how to determine the sulfate content in water by cation exchange.
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-, PO43-) are subtracted from the result.
The method describes how to determine the sulfate content of water by means of a photometric cuvette test.
In the presence of barium chloride, sulfate ions form barium sulfate, which is only slightly soluble in water. The turbidity produced by doing so is determined with a photometer.