  Using symmetric 112Sn+112Sn, 124Sn+124Sn collisions as references, we probe
isospin diffusion in peripheral asymmetric 112Sn+124Sn, 124Sn+112Sn systems at
incident energy of E/A=50 MeV. Isoscaling analyses imply that the
quasi-projectile and quasi-target in these collisions do not achieve isospin
equilibrium, permitting an assessment of the isospin transport rates. We find
that comparisons between isospin sensitive experimental and theoretical
observables, using suitably chosen scaled ratios, permit investigation of the
density dependence of the asymmetry term of the nuclear equation of state.
