Evaporation of Hypostoichiometric Plutonium Dioxide from 2070° to 2380°K

Total vapor pressures of PuO_2-x, compositions were measured gravimetrically with tungsten Knudsen cells from 2070° to 2380°K. The vapor pressure equation for the composition approximating the congruent one, PuO_1.82, is    
where P_c, is the pressure if the vapor is assumed to be entirely PuO₂(g). The evaporation of PuO_1.562 was univari-ant, indicating the presence of two condensed phases, and that of PuO_1.62 was bivariant from 2240° to 2380°K; this result confirms that the phase boundary of the PuO_2-x, phase remains at Pu_1.61 at temperatures close to the liquidus.