Complex formation in the system Hg (II) - 1-phenyl-2,3-dimethylpyrazoline-5-thion - 0.1 mol / l HNO<sub>3</sub> - 298 K
The process of complexation of mercury (II) ions in a medium of 0.1 mol / L HNO<sub>3</sub> at a temperature of 298 K was studied by potentiometry using a redox electrode based on 1-phenyl-2,3-dimethylpyrazoline-5-thione and its oxidized form. It is shown that titration of the Hg (II)-1-phenyl-2,3-dimethylpyrazoline-5-thione - 0.1 mol /L HNO<sub>3</sub> - 298 K system leads to a regular increase in the potential of the indicator electrode. It was found that the process of complexation proceeds stepwise with the formation of four complex forms of compositions: [HgL(H<sub>2</sub>O)<sub>3</sub>]<sup>2+</sup>, [HgL<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>]<sup>2+</sup>, [HgL<sub>3</sub>(H<sub>2</sub>O)]<sup>2+</sup> and [HgL<sub>4</sub>]<sup>2+</sup> For each complex particle, their stability constants are determined by the Bjerrum method.