This International Standard specifies a method for determining the hydroxyl value of unsaturated polyester resins. In fact, this method determines the difference between the hydroxyl value and the acid value; it is therefore necessary to determine the total acid value separately, in order to calculate the hydroxyl value. NOTE 1 The hydroxyl value of saturated polyester resins (for example, polyester resin used for the manufacture of polyurethanes and polymeric plasticizers) and of certain types of alkyd resins may also be determined by this method.