ISO 979:1974

Sodium hydroxide for industrial use — Method of assay

Method for determination of the titre; this is expressed conventionally as percentages by mass of NaOH, a) as total alkalinity and b) as caustic alkalinity, corresponding to the total alkalinity less the alkalinity due to carbonates. 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 two amounts a) and b). The mass of carbon dioxide is determined by the method specified in ISO 3196. This method has also been approved by the IUPAC. – Cancels and replaces ISO Recommendation R 979-1969 of which it constitutes a technical revision.