THE INFRARED SPECTRA OF HUMIC ACIDS AND RELATED MATERIALS

Abstract

The infrared spectra of a number of humic acids and related materials obtained by the potassium bromide pressed pellet technique are summarized. Acidic properties of humic acids are largely due to clearly defined carboxylic acid frequencies at 3.9 μ and 5.8 to 5.85 μ. These bands are shifted in the expected manner by preparation of the sodium salts. Autoclaving of humic acids from lignite and from hydroquinone removes the carboxylic acid bands and produces material having bands in the long wave-length region that are at the same position as bands shown by bituminous coal and autoclaved cellulose. The potassium bromide technique has also revealed in the infrared spectra of low rank material a band at 6.65 μ which decreases markedly with increase in rank and may be related to the degree of condensation of aromatic nuclei.