Ruthenium tetroxide selectively oxidizes activated aromatic compounds under mild conditions and has been used for the catalytic oxidation of several different coals. The quantities of the volatile monocarboxylic acids with 26 carbon atoms have been determined by an isotope dilution technique. The amount of ethanoic acid ranges from 1 to 3 mol/lOOC and the quantities of propanoic acid, and butanoic acid exceed 0.1 mol/lOOC. Methylpropanoic, pentanoic, 2-methylbutanoic, 3-methylbutanoicand hexanoic acid are formed in lesser amounts. The outcome of the experiment depends upon whether or not the coal has been extracted prior to oxidation. The results for Illinois No. 6 coal expressed in moles ofethanoic acid produced/lOOC illustrate this feature: raw whole coal, 1.9; coal extracted by the method of Hayatsu and co-workers, 1.0. Dehydrogenation with benzoquinone prior to oxidation increases the yield of ethanoic acid to 1.5 mol/lOOC. The amounts of ethanoic acid obtained from the other extracted coals are 1.0 for Texas lignite, 1.2 for Rawhide subbituminous, 3.4 for Pittsburgh No. 8, 3.3 for a higher ranking bituminous coal (PSOC726) and 0.7 for an anthracite (PSOC872). The results obtained in this study are compared with related information concerning the distribution of alkyl groups within coal by other methods.