A new approach to studying the condensation processes in the polluted atmosphere, based on the thermodynamic models, is presented. The thermodynamic models of extreme intermediate states (MEIS) can be used for analysis of system states in the course of the system relaxation toward final equilibrium. Raindrops are modeled as a diluted solution of strong electrolytes, using Debye-Hueckel statistical theory. The methods of description of surface effects, used in the model, are discussed. The mathematical simulation results are compared with the statistically analyzed data of observations of chemical composition of precipitation in different Eastern Siberian regions. Theoretical and experimental estimates of the dependence of droplet ion composition in the atmosphere on the concentration of gaseous pollutants and composition of the condensation nuclei are presented.