Susceptibility of humic acid towards sodium amalgam

Three humic acids (HA-I) of different degrees of humification were treated with HCl (1:1). The hydrolyzed humic acids (HA-II) were subsequently degraded with Na-amalgam. The reduction products were divided into the following fractions: humic acid residues (HA-III), fulvic acid (FA), and ether-extractable lubstances (Et), The humic acids used in this study were extracted from the following three soils; Inogashira (Volcanic ash soil), Kuragari (Drown forest soil, BD type), and Higashiyama (Brown forest soil, rBB type). The experimental results are summarized as follows: 1. The RF values of HA-II, in the case of Inogashira and Kuragari, were higher, and the △log K values were lower than those of HA-I. The carbon and oxygen contents of HA-II were higher while the hydrogen, and nitrogen contents were lower than those of HA-I. 2. The total amount of carbon in HA-III. FA and Et added up to about 90% of the carbon present in HA-II. The carbon of HA-III found in HA-III after reduction tended to increase in the order: Inogashira>Kuragari>Higashiyama. In FA and Et, the opposite trend was followed. In the case of Inogashira about 60% of the carbon of HA-II was found in HA-III. 3. The dark coloration of humic acid largely disappeared during the reductive treatment. As for the amorphous carbon-like structure detected in Inogashira, it was not found in the HA-III after reduction. Therefore, it was presumed that the structures destroyed or saturated during the reductive treatment were the ones responsible for the essential properties of humic acid.