A test portion is evaporated in the presence of ethanediol and the water content of the residue is determined by the Karl Fischer method with direct electrometric measurement. The method is applicable to products having water contents equal to or greater than 50 mg/kg. For water contents greater than 1000 mg/kg it is preferable to dilute the evaporation residue with anhydrous methanol in accordance with ISO 4276 and titrate an aliquot portion of the diluted solution.