AbstractAn experimental database for the precipitation of chloride and sulfate salts associated with six cations (sodium, potassium, magnesium, calcium, barium, and strontium) from aqueous solutions was generated using isopropylamine as the precipitation agent. Consistency tests performed on the acquired precipitation data indicated a high level of experimental consistency. The precipitation fractions (P) of all chloride salts (at 5,000 and 10,000 mg/L) over the studied range of solvents volume ratios (VR) were approximately identical and their small variations were within their experimental uncertainty. The P of sulfate salts (1,000 mg/L) over the studied range of VR were appreciably varied.A framework derived from thermodynamic principles of liquid‐liquid equilibrium criteria was developed to correlate the precipitation data. The activity coefficient of a given salt in a reference solvent (water) was related to the activity coefficient of such a salt in a mixed‐solvent mixture (water and organic). The power series function was employed to express the activity coefficients. Two model equations were provided by the framework: the 2‐power equation with two interaction parameters, and the 3‐power equation with three interaction parameters. While both equations were adequate for correlating the solubility phase behavior of a salt in a mixed‐solvent mixture, the 3‐power equation was more accurate.