Adsorption of nitrogen on Grafoil preplated with carbon tetrachloride at 77 K

Nitrogen adsorption on Grafoil preplated with carbon tetrachloride has been studied volumetrically at 77 K. The step in the N ₂ adsorption isotherm which is caused by the order-disorder (solid-fluid) phase transition of adsorbed N ₂ has been observed for various amounts of CCl ₄ preadsorbed. The equilibrium pressure of N ₂ at which the step appears is not affected by the preadsorption of CCl ₄. The step height decreases linearly with increasing amount of CCl ₄ preadsorbed, until the step disappears at 0.844 ± 0.053 monolayer (ML) of CCl ₄. It is suggested that the adsorbates separate into an essentially pure N ₂ phase and a phase mixture of CCl ₄ and N ₄ when the amount of CCl ₄ preadsorbed is less than 0.844 ML. It is also found that the amount of N ₂ which fills the first overlayer of the monolayer CCl ₄ is comparable to or slightly greater than the 1 ML quantity of CCl ₄.