This paper reports the calculations of parameters for the Pitzer equation and thermodynamic potentials of solid phases crystallizing in water-salt systems modeling chloride brines taking into account the presence of bromide ions in them. Solubility diagrams were calculated for corresponding ternary and quaternary systems containing chlorides and bromides of sodium, potassium, and magnesium at 25°C. The results of calculations are in adequate agreement with the available published experimental data on solubility and can be used to model salt crystallization during the concentration of seawater and brines. © Pleiades Publishing, Ltd. 2007.