This part of ISO 9963 specifies a method for the titrimetric determination of carbonate alkalinity in natural and drinking water. Using a higher pH value for the endpoint than the method specified in ISO 9963-1, the influence of other hydrogen acceptors, such as anions of humic acids, is reduced by the procedure. The method is intended for samples with a carbonate alkalinity between 0,01 mmol/l and 4 mmol/l (as H+ equivalents). For samples containing higher concentrations of alkalinity, a smaller test portion can be used for analysis. In this context, carbonate alkalinity is often called total alkalinity and usually has nearly the same numerical value as methyl orange alkalinity (MO-alkalinity). The endpoint detection, using a pH-meter is less prone to interferences than the use of the indicator.