Overview
ISO 1304:2016 - Rubber compounding ingredients - Carbon black - Determination of iodine adsorption number - specifies standardized laboratory methods for measuring the iodine adsorption number (iodine number) of carbon blacks used in the rubber industry. The document describes two titration procedures (Method A: manual titration with starch indicator; Method B: potentiometric titration with an automatic titrator) and sets out the required apparatus, reagents, sample preparation, solution preparation, titration and result expression. In case of dispute, Method B (potentiometric titration) is the preferred route.
Key topics and technical requirements
- Test principle: A dried test portion of carbon black is mixed with a measured iodine solution, centrifuged, and the remaining iodine in the supernatant is titrated with sodium thiosulfate to calculate the iodine adsorption number.
- Two titration methods:
- Method A - manual titration using a burette and starch indicator.
- Method B - potentiometric titration using an automatic titrator and combined electrode (preferred in disputes).
- Apparatus & equipment: analytical balances, oven (125 °C), volumetric glassware, calibrated pipettes/burettes or digital dispensers, mechanical shaker, centrifuge, magnetic stirrer, and automatic titrator (for Method B).
- Reagents & solutions: iodine/potassium iodide solution, sodium thiosulfate, potassium iodate/iodide primary standard, diluted sulfuric acid, n‑amyl alcohol, starch indicator (Method A). Preparation and standardization steps are specified in the standard.
- Limitations & interpretation:
- The iodine number is related to carbon black surface area and generally agrees with nitrogen surface area measurements, but can be significantly depressed by volatile or solvent‑extractable materials and affected by ageing of carbon black.
- Therefore the iodine adsorption number does not always equate to specific surface area; interpret results in context.
- Quality control: procedures for verification using standard reference blacks and an informative annex on precision are included.
Applications and who uses it
ISO 1304:2016 is used for:
- Quality control laboratories in carbon black manufacturing and rubber compounding plants.
- Rubber compounders and tyre manufacturers evaluating filler surface properties.
- Independent testing laboratories and R&D teams comparing surface activity or batch consistency.
- Procurement and specification teams who need standardized test data for supplier acceptance.
Keywords: ISO 1304:2016, iodine adsorption number, carbon black testing, potentiometric titration, rubber compounding, iodine number, surface area measurement, quality control.
Related standards
- ISO 1126 - Carbon black - Determination of loss on heating
- ISO 385, ISO 648, ISO 1042 - laboratory glassware calibration and use (referenced in ISO 1304:2016)