Distribution of Complexes and Ligands in the Solution

it is also necessary to evaluate [L] dependence on the solution pH by making use of the equilibrium constants of this type, 

in a general case to calculate the composition of the complex system, the material balance equations are necessary. If we assume that complexes of ML, type form in the monoligand system, and protonated ligand LH is unable to form coordination bonds with M ions, it follows from Eqs. (1.4), (1.7), (1.8), and 

It should be noted that data about formation of mixed complexes in this system could also be found. For example, in interpreting the data of potentiometric titration, the opinion was expressed [14] that with the aforementioned compounds such complex ions as Zn(CN)g(OH) or Zn(CN)3(OH)2 can be formed. However, the existence of the latter complexes has not been supported by other independent methods thus far therefore, there is no final answer to this question. Mixed complexes can form in other systems as well, for example, in alkaline Cu(II) solutions containing various ethanolamines. 

This is determined by relevant changes in chemical equilibria. This phenomenon is impossible in the solutions of simple salts. 

The effect of temperature on the distribution of complexes is not definitive either. It is especially difficult to forecast when the solution contains forms of protonated ligand, which are unable to form coordination compounds with metal ions. The Cu(II)-ethylenediamine system in which such particles as Cu, CuL , CuL , L, LH, and form (here, ethylenediamine is symbolized 

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