Thermodynamic properties of lanthanum molybdates

The enthalpy of solution of LаОНMoO₄ and Cs₂MoO₄ in aqueous HCl at 298 К has been determined by solution calorimetry, and the standard enthalpy of formation of lanthanum hydroxomolybdate has been calculated. The enthalpies of solution of NaLa(MoO₄)₂ and Na₅Lа(MoO₄)₄ in molybdate melt at 973 K have been determined by high-temperature melt solution microcalorimetry, and the high-temperature enthalpies of the double molybdates in the 298–1000 K range have been measured by the mixing method. The standard enthalpies of formation of the double molybdates have been calculated using data available from the literature. The low-temperature heat capacity of NaLa(MoO₄)₂ in the 60–300 K range has been measured on an adiabatic vacuum calorimeter. The basic thermodynamic properties of NaLa(MoO₄)₂, Na₅Lа(MoO₄)₄, and LаОНMoO₄ have been calculated.