This part of ISO 9963 specifies a method for the titrimetric determination of alkalinity. It is intended for the analysis of natural and treated water, and waste water, and can be used directly for waters having an alkalinity concentration of up to 20 mmol/l. For samples containing higher concentrations of alkalinity, a smaller test portion can be used for analysis. The recommended lower limit is 0,4 mmol/l. Suspended matter in the form of carbonate may interfere with the analysis. This interference can be reduced by filtration prior to the titration. The endpoint detection, using a pH-meter, is less prone to interferences than the use of the indicator.