The alkaline permanganate oxidation of organic substances selected for their bearing upon the chemical constitution of coal

In Part VIII of the previous papers upon the Chemistry of Coal from these laboratories (Bone, Parsons, Sapiro and Groocock 1935) it was shown that on oxidation by means of boiling alkaline permanganate the main organic substance of the lignin → peat → coal → anthracite series yields carbon dioxide, acetic, oxalic and benzene carboxylic acids, the proportions of the last named to the oxalic acid produced increasing with the maturity of the coal substance. Also, while every benzene carboxylic acid, except benzoic acid itself, was isolated from the oxidation products of some coal or other, in each and every case examined the penta- or hexacarboxylic acid predominated. Another notable result was that whereas no phthalic acids were detected among the benzenoid acids produced from lignins, and comparatively small proportions among those yielded by peats and brown coals, larger proportions thereof were yielded by bituminous coals and anthracites. The results as a whole, while strongly supporting the view of the essential chemical continuity of the lignin → peat → coal → anthracite series, and of lignins rather than celluloses being its chief progenitors, suggested the possibility of the main coal substance having arisen through condensations of phenolic and amido-bodies with aldehydic bodies—much as systematic resins are now produced—and more recent observations have pointed to high pressures, rather than temperature, having been the principal factor in the natural maturing of the coal substance.