Solubility products of MgO in molten (KCl + SrCl2) with composition corresponding to congruent compound K2SrCl4 at T = 923, 973 and 1023 K were determined by a potentiometric titration method using Pt(O-2)vertical bar ZrO2(Y2O3) indicator electrode. The solubility product indices (p(Ks, MgO), mole fractions) were found to decrease with the temperature elevation by such a manner (9.92 +/- 0.13) at 923 K, (9.34 +/- 0.11) at 973 K and (9.08 +/- 0.13) at 1023 K. The slope of logK(s,) (MgO) - T-1 plot in the studied temperature range (ca. 76 kJ.mol (1)) corresponds to value of fusion enthalpy of MgO (77 kJ.mol (1)). A comparison of MgO solubilities in the molten K2SrCl4 with the similar results obtained for (CsCl + KCl + NaCl) (0.455: 0.245: 0.300) and (KCl + LiCl) (0.41: 0.59) eutectic melts shows that the values for K2SrCl4 melt are intermediate between those for low-acidic (CsCl + KCl + NaCl) and merely acidic (KCl + LiCl). The oxobasicity indices pIL of K2SrCl4 in the studied temperature range change from 2.26 to 2.45 with the temperature rise. (C) 2016 Elsevier Ltd.