Surface Area of Nonporous Carbon Blacks and Area of the Adsorbed Nitrogen Molecule

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Abstract
Surface areas of completely nonporous carbon blacks of widely varying particle chain formation (structure) have been determined by means of the nitrogen adsorption method as well as by electron micrography. Accurately determined densities in helium were used as the basis of calculations in the latter approach. It was found that the ratio of areas measured by nitrogen adsorption to electron micrographically determined surface areas is greatly dependent upon chain formation. A higher structural build-up leads to a lower ratio, explained by the observation that fusion areas in carbon chains are necessarily, though erroneously, counted as surfaces in electron micrography. The ratio differs markedly from unity, however, in low structure blacks, where fusion areas are negligible. By accepting the area of a nitrogen molecule adsorbed in a monolayer as being equal to that in the solid state, 13.8 A2, the ratio becomes unity for nonporous low structure blacks. It appears likely, therefore, that all surface area data based on the area of a nitrogen molecule in the liquid state of 16.2 A2 are too high by about 15 per cent of presently accepted values.

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