  The differences between the experimental and the theoretically calculated
binding energies in Relativistic Mean Field (RMF) approach have been calculated
for a large number of odd-$Z$ nuclei from $A=47$ to 229. Neutron-proton (n-p)
interaction is expected to be the major contributor to this difference. This
difference, excluding certain mass regions and taking other effects as well as
the odd-even mass difference into account, may be linearly parametrized by the
Casten factor, a recognized measure of the n-p interaction in the nucleus. The
results follow the same pattern as in the case of even-$Z$ nuclei observed
earlier.
