Kaon and proton ratios from central Pb+Pb collisions at the CERN SPS

K-/K+ and (p) over bar/p ratios measured in 158 A.GeV Pb+Pb collisions are shown as a function of transverse momentum P-T and centrality in top 8.5% central region. Little centrality dependence of the K-/K+ and (p) over bar/p ratios is observed. The transverse mass m(T) distribution anti dN/dy of K+, K-, p and (p) over bar around mid-rapidity are obtained. The temperature T-ch and the chemical potentials for both light and strange quarks (mu(q),mu(s)) at chemical freeze-out are determined by applying simple thermodynamical model to the present data. The resultant mu(q),mu(s) and T-ch are compared with those obtained from similar analysis of SPS S+A and AGS Si+A data. The chemical freeze-out temperature T-ch at CERN energies is higher than thermal freeze-out temperature T-fo which is extracted from m(T) distribution of charged hadrons. At AGS energies T-ch is close to T-fo.