  We study the phase transition of asymmetric hadronic matter to a quark-gluon
plasma within the framework of a simple two-phase model. The analysis is
performed in a system with two conserved charges (baryon number and isospin)
using the stability conditions on the free energy, the conservation laws and
Gibbs' criteria for phase equilibrium. The EOS is obtained in a separate
description for the hadronic phase and for the quark-gluon plasma. For the
hadrons, a relativistic mean-field model calibrated to the properties of
nuclear matter is used, and a bag-model type EOS is used for the quarks and
gluons. The model is applied to the deconfinement phase transition that may
occur in matter created in ultra-relativistic collisions of heavy ions. Based
on the two-dimensional coexistence surface (binodal), various phase separation
scenarios and the Maxwell construction through the mixed phase are discussed.
In the framework of the two-phase model the phase transition in asymmetric
matter is continuous (second-order by Ehrenfest's definition) in contrast to
the discontinuous (first-order) transition of symmetric systems.
