Separation of the Groups of Humic Substances upon Recurrent Treatment with Solvents

Abstract

The recurrent (up to 20 times) reprecipitation of an alkaline extract from the Al horizon of dark gray forest soil by acids at pH 1.5 does not provide a complete separation of the acid-soluble fraction from the acid-insoluble residue of humic substances. A satisfactory separation of the residue into hymatomelanic and humic acids can be achieved by several treatments with dioxane, provided that the residue is subjected to reprecipitation before every extraction procedure.