Relates to the analysis of a possible excess of acidity or alkalinity. Detection by dissolution of a test portion in water. Addition of a known excess of standard volumetric suphuric acid solution in the presence of methyl red. Elimination of the carbon dioxide by boiling. Titration of the excess of acid with standard volumetric sodium hydroxide solution. Calculation expressed as sulphuric acid or sodium carbonate depending on whether the quantity of acid found is higher or less than the known quantity introduced.