ARGON-ETHYLENE LAYER FORMATION ON GRAPHITIZED CARBON BLACK

Argon isotherms have been measured on various coverages of ethylene on graphitized carbon black in the range 64-78°K. The molecular area of ethylene at 77°K was estimated to be 17.8-18.8 Å2. This value corresponds best with a model of ethylene molecules rocking to and fro on the carbon surface. The prefrozen layer methods of Halsey have been extended to a system in which capillarity is a complication. The maximum thickness of the ethylene film was found to be 2 layers. Argon Vm lowering on ethylene was observed and attributed to loose packing of argon rather than to ethylene capillarity or surface roughness of carbon. A two-dimensional phase transition, presumably of the liquid → solid type, has been observed for the first time on a prefrozen layer system.