Pittsburgh No. 8 coal, whose average short-range structural domain contains approximately three parallel layers separated by an average inter-layer distance of 3.9 Angstrom, forms a stable adduct with aniline. In this adduct, the inter-layer structuring characteristic of Pittsburgh No. 8 coal is not disrupted to an extent measurable by wide-angle x-ray scattering methods. No such adduct is formed when Pittsburgh No. 8 coal is treated with toluene, with triethylamine, with tetrahydrofuran, or with chlorobenzene.