ISO 3138:1974

Anhydrous hydrogen fluoride for industrial use — Determination of non-volatile acid content — Titrimetric method

Applicable to contents of between 0.005 % (m/m) and 0.3 % (m/m) expressed in sulphuric acid. Preparation of the samples according to ISO 3137. Removal of volatile acids by evaporation and titration of the remaining acidity with standard volumetric sodium hydroxide solution in the presence of phenolphthalein as indicator. The evaporation is carried out on a boiling water bath in a fume cupboard.