Sublimation of Strontium Sulfide and the Dissociation Energy of SrS

The sublimation of strontium sulfide in the temperature range 1543° to 2122°K was studied by mass spectrometric and vacuum balance effusion techniques. Partial pressures of the vapor species Sr, S, S2 and SrS were derived. Results are compared with those of Marquart and Berkowitz and of Colin, Goldfinger and Jeunnehomme. Best values obtained from second- and third-law calculations based on the dissociation energy of sulfur D0(S2) = 101 kcal/mole give the following heats of reaction: SrS(s)=SrS(g),ΔH0∘=132±4 kcal/mole,SrS(s)=Sr(g)+S(g),ΔH0∘=212±5 kcal/mole,SrS(g)=Sr(g)+S(g),ΔH0∘=80±4 kcal/mole=3.5±0.2 eV,S(s)+Sr(s)=SrS(s),ΔHf,298∘=−108±4 kcal/mole.