  Phase transitions of first and second order can easily be distinguished in
small systems in the microcanonical ensemble. Configurations of phase
coexistence, which are suppressed in the canonical formulation, carry important
information about the main characteristics of first order phase transitions
like the transition temperature, the latent heat, and the interphase surface
tension. The characterisitc backbending of the micro- canonical caloric
equation of state T(E) (not to be confused with the well known Van der Waals
loops in ordinary thermodynamics) leading to a negative specific heat is
intimatly linked to the interphase surface entropy.
