Mass-Spectrometric Study of the Sublimation of MnS(s) and the Dissociation Energy of MnS(g)

Abstract

Mass-spectrometric measurements on stoichiometric MnS and a mixture of MnS and graphite in tungsten crucibles show that the former vaporizes congruently to produce Mn(g) and ½S2(g) and that the latter system reacts to form Mn(g) and CS(g). Small quantities of MnS+, MnS2+, MnS3+, sulfur polymers, and possibly Mn2+ and Mn3+ were also observed. Intensity measurements on Mn+, S+, S2+, and MnS+ and previously measured decomposition pressures of MnS were combined in a third-law treatment to yield for the dissociation energy of MnS(g) 71±4 kcal/mole. The associated heat of formation from solid elements is 67±6 kcal/mole. The thermodynamic results are given in Eqs. (4) to (9). Very approximate values of energies for dissociation of a sulfur atom from MnS2 and MnS3 are given.