The infrared identification of a humo‐polysaccharide ester in soil humic acid

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Abstract
Studies involving methylation, dissolution, infrared spectroscopy and gas‐liquid chromatography were conducted with humic compounds extracted from a Greenville loam and a Cecil sandy loam. The results indicated that methylated humic acid and non‐methylated hymatomelanic acid have similar infrared characteristics, with intense C‐H absorption at 2980 ‐ 2920 cm‐1, and strong C=0 stretching but with very weak C00‐ stretching at 1720 and 1650 cm‐1 respectively. Gas‐liquid chromatography yielded chromatograms, having the same number of components, appearing at similar retention times. Dissolution separated hymatomelanic acid into fraction A, with humic acid characteristics; and fraction B, a polysaccharide. This separation released the infrared carboxyl peak at 1650 cm‐1 in fraction A. It was concluded that hymatomelanic acid was a naturally occurring ester compound, composed of humic material in ester linkages with polysaccharide.