Surface Tension Measurements of Surface Freezing in Liquid Normal Alkanes
X. Z. Wu 1,
B. M. Ocko 2,
E. B. Sirota 1,
S. K. Sinha 1,
M. Deutsch 3,
B. H. Cao 1, and
M. W. Kim 1
1 Corporate Research Science Laboratory, Exxon Research and Engineering Co., Annandale, NJ 08801
2 Physics Department, Brookhaven National Laboratory, Upton, NY 11973
3 Physics Department, Bar Ilan University, Ramat Gan 52900, Israel
Surface tension measurements reveal surface freezing in liquid n-alkanes. A solid monolayer of molecules is found to exist up to 30°C above the bulk freezing point. This surface phase exists only for carbon numbers 14 n
50. The measured carbon number and temperature dependence of the surface tension is interpreted within a simple thermodynamical model based on known bulk latent heat data and surface energy considerations. The vanishing of the surface phase for n
14 is a possible transition from surface freezing to surface melting behavior.
Submitted on April 1, 1993
Accepted on June 22, 1993