RELATION BETWEEN SOLUBILITY OF COAL-TAR PITCHES AND COMPOSITION OF THEIR VOLATILE FRACTION

The connection between the composition of the volatile fraction and th e solubility of coal tar pitches as a whole is tested. Nine coal tar p itches were extracted with several organic solvents, using the same pr ocedure, and the extract yields were determined. The same solubility s equence of these pitches was found for all the solvents, and the most soluble pitches had the smallest C/H atomic ratio. The volatile fracti on of the pyridine extract of each pitch was characterized quantitativ ely and the relations between the composition of this fraction and pit ch solubility were examined. It was found that pitch solubility was cl osely related to the concentration ratio of a benzo-derivative of a po lycyclic aromatic compound and its parent hydrocarbon. It is concluded that a study of the volatile fraction is a valuable approach towards understanding the properties and behaviour of coal tar pitches.