  The symmetry energy effects on the location of the inner edge of neutron star
crusts are studied. Three phenomenological models are employed in order to
check the accuracy of the well known parabolic approximation of the equation of
state for asymmetric nuclear matter in the determination of the transition
density $n_t$ and transition pressure $P_t$. The results corroborate the
statement that the error due to the assumption that a priori the equation of
state is parabolic may introduce a large error in the determination of related
properties of a neutron star as the crustal fraction of the moment of inertia
and the critical frequency of rotating neutron stars.
