Thermochemistry of uranium compounds VII. Solution calorimetry of α- and β-Na2UO4, standard enthalpy of formation of β-Na2UO4, and the enthalpy of the α to β transition at 298.15 K☆

Abstract The enthalpies of reaction of α- and β-Na 2 UO 4 with 1 mol dm −3 HCl were found to be −(41260 ± 21) and −(44574 ± 28) cal th mol −1 , respectively, at 298.15 K. Thus, the enthalpy difference between the α- and β-compounds is (3314 ± 35) cal th mol −1 , and ΔH o (β-Na 2 UO 4 , c, 298.15 K) = −(442.25 ± 0.85) kcal th mol −1 .