ABSTRACT
Molecular parameters of humic substances include such fundamental characteristics as the mean molecular mass, shape and size of molecules, degree of polydispersion and the nature of molecular mass distribution. In the chemistry of humic substances there is as yet no commonly accepted terminology for molecular parameters. The optimistic conclusions based on wide introduction of gel filtration for estimating molecular mass, polydispersion and the heterogeneous nature of humic substances is due to the distinctive and considerable information in the data obtained. On the whole, inferences relative to the shape and size of HA particles as also their solvation based on viscosimetric data, are contradictory and do not always accord with the results of studies by other methods. Humic acid molecules are generally considered predominantly two member systems consisting of ‘nuclei’ and peripheral chains. With this somewhat arbitrary assumption, the higher viscosity of humates of sodpodzolic soils could be explained by absolute enrichment of high mass molecules of HA with peripheral chains.
