A Study on Chromium-Humic Complexation: Part 1. Characterisation of Humic Substances

The natural humic and fulvic acids were extracted and fractionated from the soils of two tea-estates of Jalpaiguri district of West Bengal, and the synthetic humic acids were prepared in the laboratory from hydroquinone and α-amino acids, namely glycine and valine. Both the natural humic/fulvic acids and the synthetic humic acids were characterized in terms of important properties, namely functional group contents by pH-potentiometric titration, viscosity-average molecular weight, surface excess by surface-tension measurements, as well as the visible spectrophotometric properties. The fulvic acids had more total acidity than did the corresponding humic acids of both types. The naturally occurring humic acids were more complex in structure with essentially hydrophobic nature as compared to the corresponding fulvic acids and synthetic analogues of humic acids.