A mixture of KNO3 and (Li0.435Na0.315K0.25)(2)CO3 showed molten salt liquid-liquid immiscibility at 773 K. The XRD patterns of sampled upper and lower portions of the molten salts in a crucible differed greatly and respectively showed patterns resembling those of KNO3 and (Li0.435Na0.315K0.25)(2)CO3. A clear phase boundary observed in the molten state remained in solidified salts. The compositions of the aliquots sampled at upper and lower liquids were determined respectively as Li0.04Na0.10K0.86(NO3)(0.82)(CO3)(0.09) and (Li0.44Na0.27K0.29)(2)(NO3)(0.08)(CO3)(0.96). By adding SrCO3 and Cs2CO3 to the separated liquids, Sr2+ was found to exist exclusively in the lower carbonate-rich liquid, and Cs+ distributed in the upper liquid: the lower liquid by 91:9. The distribution ratio of cations between the two liquids can be predicted using Coulombic potentials calculated from their ionic radii. (C) 2016 The Electrochemical Society. All rights reserved.