A set of pyridine soluble coal extracts, previously characterized by Fourier transform infrared spectroscopy using the KBr pellet technique, are now characterized using diffuse reflectance. The ratios of the aromatic to aliphatic CH band areas are plotted against the ratio’s of the aromatic to aliphatic CH contents determined by proton NMR, thus allowing the determination of the ratio of average absorption coefficients. This quantity varies with coal origin but also differs from that obtained using KBr pellets. This latter procedure produces superior correlations and is to be preferred for accurate quantitative work.