The determination and chemical nature of fulvic acid
Pochvovedenie Pedology : 714-723
It was possible to separate from the illuvial humus horizon (Bh) of podzolized soils of the Kola peninsula a group of fulvic acids in the form of their ammonium salts. The organo-mineral gel freshly precipitated from this horizon at pH 5 was treated 3-4 times with (NH4)2CO3 soln. and heated for 30 min. on the water bath, causing the fulvic-acid fraction to go into soln. as an ammonium salt. The soln. was filtered through a Chamberland filter, and the excess of NH3 removed by evaporation. A clear, intense yellow-orange soln. was obtained. These fulvate solns. could be separated into fractions precipitated and not precipitated by Ba(OH)2 or Ca(OH)2. The latter is the lighter colored, but contains a higher % of C than the other. The darker fraction predominated in the Bh horizon of podzolized soils, the lighter fraction in the A horizon of chernozems. Solns. of free fulvic acids were prepd. by electrodialyzing solns. or suspensions of NH4, Ba and Ca fulvates. The fulvic acids so obtained were solns. which would not pass through a membrane filter. They were more dispersed than humic acids. The elementary composition of different samples varied very little. Typical data were: C 44.5%, H 5.6%, O 48.7%, N 1.2%; pH 2.76; base-absorbing capacity 620 mg. eq., equivalcnt wt. 160.