부산대학교 도서관

The standard enthalpy of formation of sodium dimolybdate was determined by dissolution calorimetry based on the measured enthalpies of dissolution of Na2CO3, MoO3, and Na2Mo2O7 in a 0.2 M NaOH solution and the literature data: ΔfH0(Na2Mo2O7, 298.15 K) = −2245.3 ± 6.3 kJ/mol. The lattice enthalpy was calculated using the Born–Haber cycle: –54 730 kJ/mol. The wavelength of luminescence radiation decreased from 650 to 540 nm on passing from sodium molybdate to sodium tungstate, and the lattice enthalpy decreased from –54 730 kJ/mol (Na2Mo2O7) to –49 030 kJ/mol (Na2W2O7). The temperature dependence of the heat capacity of sodium dimolybdate was determined in the temperature range 320–785 K. There are no phase transitions in this range.