A tentative approach to the molecular structure of humic acids: The spectral evidence for a derivation of humic acids from plant-borne esters. 2. Infrared and chemical analyses.

It is suggested that: humic acids are polyesters, originate as monomers in the secondary metabolism of both higher and lower plants, and are formed in an acid environment (including high-moor peat); the formation of humic acids is promoted by desiccation, particularly under alkaline conditions; humic acids exhibit keto-enol tautomerism, can form semi-quinones and therefore stable radicals also, and derive their colour from these radicals. (Abstract retrieved from CAB Abstracts by CABI’s permission