  We show the possibility of extracting important information on the symmetry
term of the Equation of State ($EOS$) directly from multifragmentation
reactions using stable isotopes with different charge asymmetries. We study
n-rich and n-poor $Sn + Sn$ collisions at $50AMeV$ using a new stochastic
transport approach with all isospin effects suitably accounted for. For central
collisions a chemical component in the spinodal instabilities is clearly seen.
This effect is reduced in the neck fragmentation observed for semiperipheral
collisions, pointing to a different nature of the instability. In spite of the
low asymmetry tested with stable isotopes the results are showing an
interesting and promising dependence on the stiffness of the symmetry term,
with an indication towards an increase of the repulsion above normal density.
