The interaction of hydrogen sulphide with films of nickel and tungsten has been studied over the temperature range -80" to 100°C. Rapid dissociative adsorption, followed by desorption of hydrogen occurred on both metals. The average composition of the surface phase was expressed as H,S and n decreased with increase of both surface coverage and temperature. Adsorption of hydrogen sulphide on silver films at -80°C caused sintering to occur ; a substantial fraction of the adsorption was reversible but some dissociation also took place.The completion of the surface layer on nickel at 0°C was followed by the formation of bulk sulphide. Activation energies for the incorporation process were determined as the thickness of the sulphide layer increased over the temperature range 0" to 90°C. No clear evidence for incorporation on tungsten was obtained at temperatures below 100°C but a slow process was observed on silver films between 150" and 260°C.Evidence for two kinds of adsorbed hydrogen atoms was found by exchange experiments with deuterium on films of nickel and tungsten partially covered with hydrogen sulphide.

The interaction of methyl mercaptan with evaporated films of nickel and tungsten has been investigated in the temperature range -80" to about 140°C. Dissociative adsorption occurred on nickel at -80°C and hydrogen and some methane were desorbd. Sulphidation of the metal began at 0°C with the evolution of methane but above 40°C a second reaction involving the formation of dimethyl sulphide and hydrogen became important. The factor controlling the changeover in mechanism appeared to be tbe concentration of adsorbed hydrogen atoms on the surface which decreased with rise in temperature. Activation energies for the evolution of the various gases were determined ; substantial sulphidation took place by the second reaction with a value of 10 kcal/mole which was independent of the thickness of the sulphide layer.Dissociative adsorption together with some molecular adsorption occurred on tungsten at -80°C.Hydrogen, and with rise in temperature, methane, were evolved but no dimethyl sulphide was formed and no incorporation of sulphur took place below 100°C.

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