Fuchs humic acid structure

Figure 1.22. Fuchs model for humic acid structure. From Swain (1963). Reprinted by permission of Pergamon Press.

Concepts of the compositions of coals influenced many in considerations of the structures of soil HS. For example, the proposal of Fuchs (1931) for structures of coal HAs (Figure 1.1) influenced soil humic scientists. The proposed structure is composed of heterocyclic aliphatic functionalities, some phenol-derived units, and considerable amounts of carboxylic and hydroxyl acidic functionalities. It may be possible that such structures could arise under conditions of elevated temperature and pressure, with oxidation taking place subsequently. Whereas such conditions might prevail during the synthesis of coals, they would be most unlikely to take place during the transformations of organic materials in the soil environment. 

Figure 1.1. Structure of humic acid as proposed by Fuchs (1931).

Concurrent investigations into the chemistry of brown coals and their humic acids, such as those carried out by the German scientist Fuchs (1930, 1931), had a great influence on the study of soil humus. Many of the techniques that were applied to coal humic acids, including the determination of COOH and phenolic OH groups, had general applicability to the study of soil humic substances. Fuch s scheme for the structure of humic acid (Fig. 1) has been widely quoted in the soils literature. 

---

See also in sourсe #XX -- [ ]

---