The iodine adsorption number of carbon black is in direct proportion to the surface area. This relationship is useful in characterizing carbon black. However, the adsorption number is also influenced by the presence of volatile substances, the porosity of the surface, and the presence of extractables.
This Application Note describes the fully automated determination of the iodine adsorption number.
Carbon black (expected IAN = 118.8 mg/g)
An appropriate amount of sample is placed in a desiccator and dried for 1 h at 105 °C and then cooled to ambient temperature.
For this determination, all solutions should be prepared one day in advance and stored in brown glass bottles to protect the fresh solutions against light.
The blank is determined by a technique identical to the sample, but without any sample.
Precisely 0.8–1 g of sample is weighed into the sample beaker. A magnetic stirrer bar is introduced and then the sample beaker is placed on the sample rack. Now 50 mL of iodine solution is dosed into the sample beaker and the suspension is stirred for 180 seconds.
After waiting for another 180 seconds for the solution to settle, with the stirrer switched off, 5 mL of the sample solution is passed through the tubing and filter as the first pre-rinse, and this is repeated for a total of four times.
Finally, 10 mL of the filtered solution is added into the external titration vessel, and the solution is now made up with distilled water. The stirrer is switched on in this vessel, following which the titration of the sample proceeds using c(Na2S2O3) at 0.0394 mol/L until the equivalence point.
During the titration, iodine solution is passed through the tubing and filter to flush back any residual solution into the sample beaker on the rack. The iodine solution is also connected to the Transfer Dosing Unit. Once the titration is complete, the pumps are switched on to clean out the external titration equipment.
The filter exchange is dependent on the sample used and must therefore be decided on the basis of past experience.
This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.
For more information on this source, please visit Metrohm AG.