Calorimetry and neutron diffraction have been used to identify and characte
rise the formation of a solid monolayer of pentane adsorbed on graphite and
coexisting with liquid pentane. The observed behaviour is quite different
from other alkanes in that the monolayer does not melt above the melting te
mperature of the pure pentane but at a temperature very similar to that of
the bulk material. The lower melting point of the bulk pentane in the penta
ne/graphite system, when it is present in a relatively small amount, allows
the melting point of the solid monolayer to be clearly resolved.