Viscosimetric characteristics of humic acid

One of the authors, KUMADA (I), has proposed a new classification of humic acids based on their colour and spectral characteristics in the visible and ultra-violet regions. Humic acids can be grouped into four major types by this procedure (A, B, Rp and P types) and evidence for a classification diagram based on the values ΔlogK and RF has recently been presented (2). It is clearly important that the usefulness of this new classification should be investigated by considering other chemical and physical properties of humic acids.