chemical thermodynamics of neptunium and plutonium - U.S. ...

290 13. Neptunium group 2 (alkaline-earth) compoundsCODATA compatible auxiliary data the value f H ◦ m (Ba 3NpO 6 , cr, 298.15 K) = −(3085.6 ± 9.6) kJ·mol −1is obtained from a recalculation in this review. The value is accepted here.13.2.2 Barium alkaline-earth compoundsEnthalpy of formation data have been reported for three barium alkaline-earth compounds,the perovskite-type oxides of the form Ba 2 MNpO 6 (cr) with M = Mg, Ca andSr.No entropy or Gibbs energy values are available for these compounds.13.2.2.1 Ba 2 MgNpO 6 (cr)Based on the enthalpy of reaction of Ba 2 MgNpO 6 (cr) with 1 M HCl reported by Morss,Fuger and Jenkins [82MOR/FUG] and auxiliary data discussed in Appendix A, f H ◦ m (Ba 2MgNpO 6 , cr, 298.15 K) = −(3096.9 ± 8.2) kJ·mol −1is calculated and accepted in this review.13.2.2.2 Ba 2 CaNpO 6 (cr)The value of the heat of solution of Ba 2 CaNpO 6 (cr) in 1 M HCl was reported byGens et al.[85GEN/FUG] from nine replicate measurements on two well-characterisedsamples. From this and auxiliary data in Appendix A, the recommended valueis calculated. f H ◦ m (Ba 2CaNpO 6 , cr, 298.15 K) = −(3159.3 ± 7.9) kJ·mol −113.2.2.3 Ba 2 SrNpO 6 (cr)The value of the heat of solution of Ba 2 SrNpO 6 (cr) in 1 M HCl was reported byGens et al.[85GEN/FUG] from nine replicate measurements on two well-characterisedsamples. From this and auxiliary data in Appendix A, the recommended valueis calculated. f H ◦ m (Ba 2SrNpO 6 , cr, 298.15 K) = −(3122.5 ± 7.8) kJ·mol −1