  The recent {\em ASCA} results show that the iron abundance of the X-ray gas
of elliptical galaxies is less than the solar abundance ($Z_{\sun}$). The
observed low iron abundance is inconsistent with the predictions of the
previous chemical evolution models. In order to solve this problem, we present
a simple model of chemical evolution for elliptical galaxies after the galactic
wind period under the assumption that the gases ejected from stars do not mix
with the circumferential gas. The ejected gas components evolve separately
according to their birth time and origin. We have investigated their evolution
qualitatively. The gas components originated from supernova remnant shells cool
and drop out of the hot gas faster than the other components because of their
high density and metal abundance. As a result, supernovae cannot heat the whole
gas of the elliptical galaxies effectively, in contrary to the previous
results. If the metal abundance of mass-loss gas is not uniform, the mass-loss
gas with higher abundance also easily drops out and the average abundance can
decrease. We believe that this is a hint of solving the low abundance problem.
