Method for determination of the titre, conventionally expressed as percentages by mass of KOH. There are three ways: a) total alkalinity, b) caustic alkalinity corresponding to the total alkalinity less the alkalinity due to carbonates and c) actual potassium hydroxide corresponding to the total alkalinity less the alkalinity due to carbonates and any hydroxide which may be present. The principle consists in titration of the total alkalinity with standard volumetric hydrochloric acid solution in the presence of methyl orange as indicator. Calculation of the three amounts a), b), and c). - Replaces ISO Recommendation R 990-1969.