Sulphate reacts with barium ions forming a precipitate of barium sulphate. Under defined conditions this turbidity can be used for concentration measurements.
Turbidities of the sample interfere and have to be filtered. Good reproducibility is obtained for drinking, surface and ground water. For polluted waste waters low concentrations are measured.

The determination of sulphate ions is of special importance to evaluate the aggressiveness of a water towards concrete. Sulphate, a component of natural water, is formed in many manufacturing processes and is found in waste waters even after neutralisation.