Journal of the Indian Society of Soil Science

The humic/fulvic substances extracted from the soils of Terai Agroecological region of West Bengal were characterized by potentiometric titrations, viscometric measurements, visible spectrophotometry and surface tension determinations. The results were correlated with coiling-decoiling behaviour, and aliphatic/aromatic balance of these acids. The δpH values of the humic/fulvic acids stated the polyprotic nature of the substances. The B_expt. values of the humic acids showed the higher degree of stable coiling corresponding to the fulvic acids. Humic acids exhibit much larger surface excess (τ) values than did the corresponding fulvic acids which signified the greater degree of hydrophobic character of the former than that of the latter. A sharp fall in the surface tension (γ) was also observed in aqueous solution of 0.1 M NaCl. The (E₄/E₆) ratio, showed in general, the higher amount of aliphatic moiety rather than the aromatic moiety.