Researches on the chemistry of coal. Part VI.—Its benzenoid constitution as shown by its oxidation with alkaline permanganate

In Part IV of this series a preliminary account was given of the discovery that the benzene-pressure-extracted “residue” of a typical bituminous coal can readily be oxidised by means of an alkaline solution of potassium permanganate with formation of considerable quantities of benzenoid acids, among which benzene hexacarboxylic (mellitic) and 1:2:3:4 benzene tetracarboxylic acids had been isolated and identified, the total yield of such acids obtained amounting to between 25 and 40 per cent, of the weight of the coal residue taken, according to the conditions under which the oxidation had been conducted. Seeing that the benzene-pressure-extracted “residue” treated in the experiments was 88·6 per cent, of the original coal substance, such results indicated that a considerable part of the original coal substance is of a benzenoid character, and the working out of the possibilities thereby opened up was reserved for further investigation because of its bearing upon the chemical constitution of coal. Since the publication of those results the subject has been under continuous investigation in the Fuel Research Laboratories of the Imperial College with the aid of grants from the Fuel Research Board of the Department of Scientific and Industrial Research, and the present paper gives an account of our further experiments.