Averageparticle diameters in several commercially-produced carbon blacks range from 0.01 to 0.4 micrometres, while average aggregate diameters range from 0.1 to 0.8micron.

Because of their source materials, the methods of their production and their large surface areas and surface characteristics, commercial carbon blacks typically contain varying quantities of adsorbed by-products from the production processes,particularly aromatic compounds.

Typical classes of chemicals adsorbed onto the carbon black surface are carcinogenic polycyclic aromatic hydrocarbons (PAHs), nitro derivatives of PAHs and sulphur-containing PAHs.

Historically, this analysis has been carried out manually with all sorts of problems for example; reaction times, and stirring rates of the iodine to theblack, and a coloured (black!) solution making it extremely difficult to define the colour endpoint.

10 ml of the reacted iodine/carbon black sample is pipetted via another 800 Dosino through a special filter apparatus, and into the external titrating vessel, where the redox titration with sodium thiosulphate takesplace.

The use of a 772 pump unit, attached directly to the 778 Robotic Sample Processor, guarantees an effective aspiration of the sample after titration.

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