The adsorption of methane on cyclohexane-preplated graphite has been studied volumetrically at 77 K. Methane undergoes a displacement transition as well as layer-by-layer condensation transitions, similarly to Kr studied previously. The isotherm step of the displacement transition is clear and sharp, being indicative of a first-order phase transition. The transition takes place when the adsorbed methane molecules exceed the pre-adsorbed cyclohexane in number. The results support our previous interpretation that the displacement transition is a change from the layer-on-layer mode to the two-phase mode of two-component adsorption.
