This International Standard specifies a microtitration method to measure the degree of unsaturation in polyether polyols used in the production of polyurethanes. It is based on the reaction of mercuric acetate with double bonds in the polyol. It does not apply to compounds in which the unsaturation is conjugated with carbonyl, carboxyl or nitrile groups. The product being measured must be essentially dry and free of inorganic salts, especially halides.