VAPOR PRESSURE OF LIQUID URANIUM EFFECTS OF DISSOLVED TANTALUM PHOSPHORUS SULFUR CARBON AND OXYGEN

The vaporization behavior of liquid uranium saturated with tantalum, phosphorus, sulfur, and carbon has been studied by mass effusion and mass spectrometric techniques in the temperature range 1800-2400°K. The results, combined with those previously reported for uranium saturated with oxygen, show that the activity coefficient of uranium decreases with increasing electronegativity of the dissolved component, varying from nearly unity in the case of tantalum and phosphorus to approximately 0.2 for oxygen. The vapor pressure of liquid uranium is given by the equation log p(atm) = (5.71 ± 0.17) - (25,230 ± 370)/T, and the heat of sublimation, ΔH°298, is 126.3 ± 1.0 kcal/mol. At high temperatures uranium monophosphide and uranium monosulfide are converted to the two-phase systems UP(s) + U(1) and US(s) + U(1).