The Quinone-Hydroquinone character of activated carbon and carbon black

Abstract

There are two extreme types of activated carbon and carbon black although structures intermediate between these two extremes are more usual. This work has established that in one extreme, the oxidized form (" H " carbon), the carbon has a pronounced quinonoid structure which creates a number of fixed olefinic bonds. In the other, the reduced form (" L " carbon), the structure is more aromatic and has the characteristics of a hydroquinone. Carbons having properties intermediate between those of a pure " H " or " L " carbon acquire some semiquinone characteristics and become less diamagnetic. It is experimentally shown that the chemical behaviour of these carbons parallels in many ways that of simple quinone-hydroquinone compounds. The quinonoid structure of an " H " carbon accounts for the formation of peroxygen complexes, its ability to catalyse the ionization of oxygen in the presence of an electron donor, its oxidizing properties, and its reactivity with rubber. The hydroquinone character of an " L " carbon is responsible for its ability to adsorb alkali, its reducing properties, and its ability to fog a photographic plate (" Russell effect "). The change in properties which occurs in chars carbonized above 650" C is due to the transition from an " L " to an " H " carbon.