The fulvic and humic acids of a podzol were fractionated into five fractions by means of dialysis. In each fraction the process of humification was studied through IR-spectra and the curve of neutralization. In the fractions of the fulvic acids, the acidity is due to the carboxyl groups and with the progress of humification one observes a decrease of these groups. On the contrary, in the fractions of the humic acids one observes a decrease in the carboxyl groups with the progress of humification but the neutralization capacity increases. This means that the acidity is caused in the humic acids by the phenolic OH groups. In both cases the humification progresses with a loss of carboxyl groups and a gain of OH groups.

8 pages, 4 figures, 9 references.

Peer reviewed