THE PHASE OF CONDENSATE COEXISTING WITH THE SOLID-PHASE OF NITROGEN ON GRAFOIL, STUDIED BY VOLUMETRIC ADSORPTION MEASUREMENTS OF NITROGEN

Volumetric adsorption isotherms of nitrogen at 77 K have been measured on Grafoil (compressed exfoliated graphite) preadsorbed with various amounts of cyclohexane or n-hexane. For cyclohexane preadsorption, the fluid-solid phase transition of post-adsorbed nitrogen is observed as a step on the isotherm until cyclohexane completes its monolayer, ind icating that post-adsorbed nitrogen compresses cyclohexane to convert its submonolayer phases into the monolayer phase. On the other hand, n -hexane preadsorbed at submonolayer coverage is found, just like CCl4 studied previously, to prevent nitrogen from undergoing the fluid-soli d phase transition. It is argued that n-hexane islands coexisting with pure nitrogen domains are in the higher-order commensurate submonolay er phase with nitrogen involved along its domain walls.