  We study the N/Z dependence of energy of vanishing flow or balance energy for
different isotopic series of various system masses like Ca+Ca, Ni+Ni, Zr+Zr,
Sn+Sn and Xe+Xe. We find that balance energy decreases with N/Z of the system
and follows a linear behaviour. The slope of N/Z dependence is steeper for
lighter systems like Ca+Ca and less for heavier ones like Xe+Xe.
