[en] Solution and drop-calorimetric studies of magnesium uranate are described. From the solution experiments, the standard enthalpy of formation, Δ Hsub(f)⁰(MgUO₄, c, 298.15 K) was found to be -(1857.0 +- 1.3) kJ mol^-1. The drop-calorimetric experiments gave values for the enthalpy increment [H⁰(T) - H⁰(298.15 K)] and heat capacity Csub(p)⁰(T), which, over the temperature range 298.15 to 1400 K, are best represented by the equations: [H⁰(T) - H⁰(298.15 K)]/J mol^-1 = 110.268(T/K) + 3.3398 x 10^-2(T/K)² - 7.8127 x 10^-6(T/K)³ - 35638; Csub(p)⁰(T)/J K^-1mol^-1 = 110.268 + 6.6796 x 10^-2(T/K) - 2.3438 x 10^-5(T/K)². The complete thermodynamic functions of MgUO₄ are tabulated from 298.15 to 1400 K. The spontaneity of the decomposition of BeUO₄ to its component oxides is advanced as an explanation for the non-existence of this compound. (author)