Multicomponent nature, of humic substances

Application of solubility parameter data is hindered by the multicomponent nature of humic substances, and homogeneous fractions are needed to obtain the necessary data for the macromolecules. Nevertheless, the available information shows that the best solvents for humic acids have polar,... 

In many cases authors never acknowledge that the subject of their investigation is a mixture even when such information is essential to the interpretation of the data. Somewhat more puzzling are the examples, which persist in the literature, where the multicomponent nature of humic substances is acknowledged but later ignored in the choice of experiments and interpretation of data The study of humic substances is the study of complicated, ill-defined mixtures, and many researchers appear to overlook this basic fact. 

However, considering the complicated, multicomponent nature of humic substances, with their variety of chromophores and probable variations in absorptivities, such statements must be viewed with extreme skepticism. A more reasonable inference from examining the UV-visible spectra of humic substances is that they result from the overlap of the absorbances of various chromophores (Hayes and Swift, 1978 Stevenson, 1982). As Hayes and Swift (1978) have pointed out, it is not possible to... 

---