The heats of formation and dissociation of zinc sulphide

An entrainment method has been used to measure the reduction and dissociation equilibria of β‐zinc sulphide (sphalerite) in hydrogen and nitrogen respectively. Values obtained for Δ H 1000 in the reactions studied ZnS(β)+H g (g)=Zn(s)+H 2 S(g), and ZnS(β)=Zn(g)+½S 2 (g), were 71.93 ± 1.0 and 93.51 ± 1.0 kcal/mole, respectively. The heat of formation of zinc sulphide was calculated from the reaction Zn(s) + S(rhombic) = ZnS(β), and a value of Δ H 298 =‐49.2 ± 1.0 kcal./mole was obtained. It is concluded that the observed vapour pressure of ZnS is due completely to dissociation of it into Zn and S vapour.