FIELD: chemistry.;SUBSTANCE: invention relates to soil sciences, agricultural chemistry and pharmaceutical industry, namely to a method for fractionation of brown humic acids. Method for fractionation of brown humic acids from a soil sample, comprising drying, grinding, removing organic residues and screening a soil sample, alkaline extraction of a soil lot with a solution of 0.1 N NaOH, the resultant alkaline extract is further mixed five times every 2 minutes at a speed of w=60 rpm, followed by shaking it for 10 minutes every time with a shaking frequency of f=60 cycles/min, and the separation of the alkaline extract from the soil particles is carried out by settling it for 120 minutes, wherein sampling from the alkaline extract is carried out directly from the process vessel, in which the entire process of fractionation of brown humic acids from a soil sample is carried out.;EFFECT: above described method provides shorter time of fractionation of brown humic acids and higher accuracy of determination.;1 cl, 1 dwg, 1 tbl, 2 ex
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