  The thermodynamics of solvable isotropic chains with arbitrary spins is
addressed by the recently developed quantum transfer matrix (QTM) approach. The
set of nonlinear equations which exactly characterize the free energy is
derived by respecting the physical excitations at T=0, spinons and RSOS kinks.
We argue the implication of the present formulation to spinon character formula
of level k=2S SU(2) WZWN model .
