Solid-liquid phase transition in a Gibbs monolayer of melissic acid at the $n$-hexane-water interface

A sharp phase transition from a crystalline state with the area per molecule $A=(17\pm 1)$Å$^2$ to a liquid state with $A=(23 \pm 1)$Å$^2$ at the $n$-hexane-water interface in a Gibbs monolayer of melissic acid has been revealed in data of X-ray reflectometry with the use of synchrotron radiation.