1.1 This part of ISO 3451 specifies a method for determining the ash, consisting of inorganic residue, yielded by unplasticized cellulose acetate.1.2 This method applies to unplasticized acetate free of additives, fillers, dyes or other materials which may affect the result.1.3 When plasticizers, additives, fillers or dyes which may affect the result are present, they shall be separated by a method agreed between the interested parties.1.4 The ash content at 575 ± 25 °C is a reasonable measure of the mineral salts and inorganic foreign matter in the cellulose acetate. The weight of ash obtained varies with the temperature of ignition. Higher temperatures such as 850 °C will convert calcium carbonate and other carbonates to the oxides and thus give lower values for the ash. The composition of ash may vary with the pulping process used in manufacture, which limits the significance of the ash determination in absolute terms.