Molecular weight determinations have been performed (using low-angle laser light scattering photometry) on derivatives of a series of humic acid macromolecules derived from lignite. The humate derivatives obtained from Beulah lignite by base extraction have molecular weights ranging from 1.3 x 10/sup 6/ to 4.3 x 10/sup 5/ daltons, from low and high yield extractions respectively. Mild oxidation with p-nitroperbenzoic acid gave humic acids with slightly larger molecular weights, again inversely proportional to the yields. The nature of the aliphatic bridging groups in low-rank coals has been investigated by ruthenium tetroxide oxidations using isotope dilution GC/MS methods for analysis of the product carboxylic acids derived from oxidation of the aromatic portions of the coal. The oxygen content of coals was studied using a new spectroscopic technique, high resolution x-ray fluorescence spectroscopy. This methods was investigated for direct quantitative oxygen analysis as well as for characterization of the type of oxygen bonds in coal. The content of several of the original plant substructures, such as cellulose, lignin, and waxy materials, was investigated. 21 refs., 1 fig., 10 tabs.