ISO 1304:2016 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).