  This paper focuses on the isospin properties of the asymmetric nuclear-matter
liquid-gas phase transition analyzed in a mean-field approach, using Skyrme
effective interactions. We compare two different mechanisms of phase separation
for low-density matter: equilibrium and spinodal decomposition. The isospin
properties of the phases are deduced from the free-energy curvature, which
contains information both on the average isospin content and on the system
fluctuations. Some implications on experimentally accessible isospin
observables are presented.
