Applicable to products the acidity of which is between 2 mol and 200 mol of univalent acid per kg. Two procedures are given: one is applicable to liquid products (R11, R113, etc.) and the other one to gaseous (R12, R22, etc.). The principle consists in extraction of the acids by water. Titration of the acids in the aqueous phase with standard volumetric sodium hydroxide solution in the presence of bromocresol green as indicator. A figure shows an apparatus for absorption of acids for products which are gaseous at ordinary temperatures.