The infra-red spectra of two softwood lignins are discussed with reference to the spectra of their acetyl and methoxyl derivatives. The spectra of the respective acetyl derivatives provide conclusive evidence for the presence of both phenolic and alcoholic groups in lignin and oxidized lignin, and of alcoholic groups only in the methoxyl derivatives of both these samples. Treatment of lignin with hydriodic acid in the conventional Zeisel determination of methoxyl groups eliminates the alcoholic hydroxyl groups and appears to split aliphatic ether linkages. The spectrum of lignin treated with hydriodic acid is very similar to that of brown coal, which supports previous chemical evidence that brown coal appears to be essentially " demethylated dehydrated lignin ". The progress of the isolation of lignin from wood was followed by infra-red spectroscopy.

A study was made of the products formed by treating brown coal or lignin with concentrated aqueous or ethanolic alkali at 200 �C. With brown coals a major redistribution of the oxygen-containing functional groups appeared to occur, because the products contained aliphatically linked carboxyl groups and aliphatic hydroxyl, as well as phenolic hydroxyl groups. The behaviour of lignin under the same conditions was less clear but sufficiently similar to that of brown coal to suggest that reactions of the same type were occurring in both cases. Reactions involving decarboxylation, ring scission of dihydric phenol structures, and subsequent hydrogenation are suggested tentatively as the main steps in the formation of the products. The results provide some additional evidence for the view that there is a simple chemical relation between Victorian brown coal and lignin.

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Quantitative studies have been made of the changes in the infra-red spectra of coals and chars that follow their acetylation. Those features in the spectra of the acetylated materials that are characteristic of the acetate groups were found to vary quantitatively with the chemically determined acetyl contents. Changes occurring in the hydroxyl absorption (at 3380 cm-1) as a result of pyrolysis and acetylation tend to confirm that the 5 to 7 per cent. of oxygen which is not detected in the functional group analysis of Victorian brown coals is predominantly in the form of hydroxyl groups which resist acetylation and which appear to be stable on heating to about 450 �C.