  By using an Ansatz for the pressure (measured in terms of the bag constant)
of the hadronic gas in equilibrium, we have formulated a new bag-type model for
the phase transition, i. e. the extended bag model. This allows one to take
into account the nonperturbative vacuum effects from both sides of the
equilibrium condition. We have explicitly shown that our model automatically
provides an isentropic equilibrium deconfining phase transition from the
quark-gluon plasma phase to the hadronic gas phase with a temperature and
chemical potential dependent bag pressure at the phase boundary. This makes it
possible to regulate the total entropy and baryon number in both phases, i. e.
the flow of the specific entropy per baryon across the phase boundary. We have
also determined the functional form of the temperature and chemical potential
dependence of the bag pressure outside the phase boundary.
