FREE-ENERGY OF FORMATION OF CS3PUCL6 AND CSPU2CL7

The free energy, enthalpy and entropy of formation of the compounds Cs 3PuCl6 and CsPu2Cl7 have been determined by measuring the sublimation pressures for the reactions CsCl(s) reversible CsCl(g), 2/5Cs3PuCl6(S) reversible 1/5CsPu2Cl7(S) + CsCl(g), and CsPu2Cl7(S) reversible 2PuCl 3(s) + CsCl(g). The pressures are measured using Knudsen effusion mass spectrometry over the temperature range 600 to 850 K. For the formati on of Cs3PuCl6 from CsCl and PuCl3, DELTAG298-degrees = - 77.3 +/- 8.5 kJ/mol, DELTAH298-degrees = - 82.1 +/- 7.8 kJ/mol, and DELTAS298-degr ees = - 16.2 +/- 10.9 J/Kmol. For CsPu2Cl7, DELTAG298-degrees = -39.4 +/- 3.5 kJ/mol, DELTAH298-degrees = -40.8 +/- 3.2 kJ/mol, and DELTAS29 8-degrees = -4.6 +/- 4.2 J/K mol.