Uranium Monosulfide. III. Thermochemistry, Partial Pressures, and Dissociation Energies of US and US2

A mass‐spectrometric study of the sublimation of uranium monosulfide has been performed over the temperature range 1825° to 2400°K. The data are combined with the previous measurements of absolute rate of effusion by means of a new method of calculation which effects an absolute pressure calibration of the spectrometer and allows a determination of the partial pressures of U, US, and US2 in the vapor, the enthalpies and entropies of sublimation to atoms and molecules, and the dissociation energies of US and US2. The partial pressures of U, US, and US2 at 2020°K are in the ratios 1/0.27/0.001. The data for the several sublimation processes are as follows:     Reaction                  logP (atm)ΔH2020∘ kcal/moleΔS2020∘ cal/mole·degUS(s)=US(g)logPUS=(7.606±0.091)−(31 030±190)/T142.0±0.934.8±0.4US(s)=U(g)+S(g)logPU=(7.323±0.081)−(29 600±170)/T270.9±0.1665.0±0.72US(s)=US2(g)+U(g)logPUS2=(6.36±0.26)−(33 430±580)/T288.4±3.762.6±1.2 The quoted uncertainties are standard deviations. The dissociation energies for ...