Solubility of Coal - 3. Effect of Macromolecular Structure on the Coal's Solubility.

Pyridine has been used as the standard solvent in coal chemistry before the turn of the century. However, till now there is no satisfactory explanation for its solvent ability, although practical (introduction of new solvents for coal: Ethylendiamin, Thionylchlorid) and theoretical (attempts to explain the solubility by the Hildebrand theory or by the Gutmann theory) advances have been made. Experiments using the swelling of coal, or a property which can be correlated to it, as a measure of the interaction with the solvent have shown that selected binary mixtures of non-solvents (unspecific coal solvents) can behave like specific solvents. A series of suitable solvent mixtures of varying concentration was used to demonstrate the Flory-Rehner-Equation. The mathematical description of swelling over the concentration range coincides surprisingly well with the measured data.