Hydrophobic hydration of synthetic humic acids

An attempt has been made to understand the folding-unfolding behaviour of natural humic acid-like synthetic substances in terms of the solute-solvent interaction term, the B-coefficient of the Jones-Dot equation. The B-expt/B-theo ratio is supposed to be in the range of the ratio of exposed surface area of the coiled system to that of linear chain which was computed earlier to be 1/pi. It is observed that there is deviation of this ratio from the ideal value of 1/pi, with the deviation depending not only on hydrophilic polar head groups of the synthetic substances but also on aliphatic and aromatic parts of humic substances due to 'hydrophobic hydration' phenomenon. It is also observed that the higher value of (-delta Y/delta lnC) in the surface property measurement contributes positively to hydrophobic hydration through its structure-making effect, resulting in, a higher B-terms ratio and a; greater degree of condensation, as indicated by lower (E(4)/E(6)) ratio.