ABSTRACT
Natural macromolecular organic substances-fulvic acids (FAs) take an active part in complex formation processes and stipulate migration forms of heavy metals in natural waters.
In spite of researches, experimental data on stability constants of complex compounds of FAs with heavy metals (among them zinc) are heterogeneous, and they differ in several lines from each other. One of the reasons for such a condition is ignoring an average molecular weight of the associates of FAs, which finally causes the wrong results. The complex formation process between zinc(II) and FAs was studied by the solubility method at pH = 9.0. ZnO suspension was used as a solid phase. FAs were isolated from Paravani lake by the adsorption-chromatographic method. This chapter shows that during the complex formation process, every 1/5 part of an associate of FAs, inculcates into zinc’s inner coordination sphere, as an integral ligand, so it may assume, that the average molecular weight of the associate of FAs which takes part in complex formation process equals to 1674. This part of the associate of FAs was conventionally called an active associate. The average molecular weight of the active associate was used for determination the composition of zinc fulvate complex, the concentration of free ligand and stability constant, which equals to 5.56 × 104.
