A fractional precipitation technique applied to soil humic substances

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Abstract
Soil humic substances are usually divided into humic and fulvic acid fractions according to their acid-precipitability. However, the author has now many evidences which indicate polymolecularity of humic substances (1, 2) and. hence. the routine fractionation seems to be insufficient for certain purposes. especially for the study of their physicochemical nature. Chromatography and electrophoresis have been most frequently used for further fractionation of humic acid preparations. but these procedures generally give at most 3 or 4 fractions and are not necessarily suitable for handling large amounts of preparations.