ADSORPTION HYSTERESIS AND 2D PHASE NUCLEATION OF CHLOROFORM ON GRAPHITE

The thermodynamic characterization of a chloroform (CHCl3) film adsorb ed on (0001) graphite has been performed by means of isotherm measurem ents between 206.9 and 227.7 K. The isotherms exhibit two steps before bulk condensation. The first step is assigned to a monomolecular laye r condensation, whose two-dimensional critical temperature is estimate d to be 216 K. The second step measurement provides evidence of CHCl3 adsorptive properties very different from those classically observed i n the formation of a second adsorbed layer. Slow adsorption kinetics a nd significant hysteresis in the second step domain for temperatures b elow 224.8 K are related to nucleation difficulties. A restructuration of the first adsorbed monolayer seems to be necessary in order to bui ld a bilayer whose high stability results in unusually low relative pr essures of the second steps of the isotherms.