Sapric histosols

The development of electrophoretic techniques afforded possibilities for fractionations based on charge density differences. Duxbury (1989) has reviewed applications of different electrophoretic separation methods, including zone electrophoresis, moving boundary electrophoresis, isotachophoresis, and isoelectric focusing (IEF). Preparative column electrophoresis (Clapp, 1957) and continuous flow paper electrophoresis (Hayes, 1960 summarized by Hayes et al., 1985) methods have been used to separate components isolated from sapric histosol soils. These techniques allowed separation of polysaccharides from the colored components the electrophoretograms of the colored components were diffuse, showing a continuum of components of different charge densities. 

Hayes (1960) observed that products from heating glucose with glycine in aqueous media under reflux conditions had some compositional properties and reactivities similar to those of the HAs isolated in aqueous base from a sapric histosol. The techniques used for the comparisons included differential thermal analysis (DTA) (see Figure 1.2). However, that work was done before the introduction of NMR to such studies. 

Figure 1.2. Differential thermal analysis for the humic acid fraction isolated in NaOH from a sapric histosol (1), from the acid precipitate isolated from products of the reaction of meth-ylglyoxal with glycine (2), and from the acid precipitate formed from the reaction of glucose with glycine (3), alkali lignin (4), casein (5), lignin-casein 3 1 complex (6), and lignin-casein 6 1 complex (7).

Figure 1.5. Relationship between the frictional ratio (/// ,m) and the molecular weight for different humic acid fractions isolated from a sapric histosol. The line is the theoretically derived relationship between frictional ratio and molecular weight for a randomly coiled polymer. After Cameron et al. (1972).

TABLE 4. Yields and ESR Data for Humic Acids (HA) and Fulvic Acids (FA) Extracted by Different Extractants from a H+-Exchanged Sapric Histosol"... 

In a further set of experiments Hayes et al. (1975) exhaustively extracted an H -exchanged sapric histosol with water, and then exhaustively with the series DMF-, sulfolane-, DMSO-, pyridine-, and EDA-water, 1 1 (v/v) mixtures in that order. The cumulative amounts of humic substances extracted for any succession of solvents were the same as the amounts extracted by the last solvent in the series without the aid of the others. This would suggest that the materials dissolved in the less efficient solvents were dissolved also in the more efficient members of the series. The analytical data for the different fractions closely resemble those in Table 5 for the substances extracted by the single solvent systems. 

TABLE 8. Solubilization of H+-Exchanged Fen Humic Acids (H+-HA) and Humic Substances from a H+-Exchanged Sapric Histosol Soil (H+-SHisl) in O.IM NaOH, DMSO, and Acidified DMSO... 

Tables 8 and 9 present data for extraction of humic substances from a sapric histosol and from two tropical soils using various combinations of DMSO, acid, and water. For comparison, some data are presented for solution in sodium hydroxide and neutral sodium pyrophosphate solutions. Use is made of EJEf, ratios to indicate differences in the solution conformations and/or compositions of the humic substances in the different solvent systems.

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