Abstract
A humic acid isolated from a brown soil (Typic Xerochrept) was characterized by analytical pyrolysis and chemical degradation reactions. On Curie-point pyrolysis at 610° C the humic acid yielded pyrolysis products from polysaccharides, proteins and lignins. Fatty acids and aliphatic hydrocarbons were also released. Acid hydrolysis or persulphate oxidation of the humic acid released polysaccharides, proteins and to some extent lignins and fatty acids, leaving a residue that amounted to ca. 25–30% of the initial weight. Pyrolysis of the humic acid residues indicated the abundant presence of homologous series of
n-alkanes,
n-alk-1-enes and α,ω-alkadienes. The data suggest that lignin is not a significant contributor to the most resistant part of the humic acid. Other plant components, mainly highly aliphatic biopolymers encountered in plant cuticles and suberin, are probably a significant and resistant part of humic acids.