The mixed aqueous electrolyte system containing lithium, sodium, chloride, and carbonate has been investigated using the isothermal evaporation method at 273.15 K. The stereophase diagram and the planar projection diagram have been constructed based on the Janecke method. The compositions of the equilibrated solid phases and liquid phase corresponding to equilibrium points were measured. The system contained only four single salts, sodium chloride (NaCl), lithium chloride monohydrate (LiCl center dot H2O), lithium carbonate (Li2CO3), and sodium carbonate decahydrate (Na2CO3 center dot 10H(2)O). Salt LiCl has a strong salting-out effect on the other salts. The density coefficients A(i) which were used for the calculation of density at 273.15 K were obtained by fitting. The calculated values of density using an empirical equation have a maximum relative error less than 0.020.