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NEN-ISO 1304 specifies methods for the determination of iodine adsorption number of carbon blacks for use in the rubber industry. Two titration methods are described: - method A: titration using a burette and starch as indicator; - method B: potentiometric titration with an automatic titrator. The iodine adsorption number is related to the surface area of a carbon black and is generally in agreement with the nitrogen surface area. However, it is significantly depressed in the presence of a high content of volatile or solvent-extractable materials; the iodine adsorption number therefore does not always provide a measure of the specific surface area of a carbon black. Ageing of carbon black can also influence the iodine number. In case of dispute, the preferred method is method B (potentiometric titration).