  The present knowledge about hadrons produced in relativistic heavy ion
collisions is compatible with chemical freeze-out happening when the energy
density divided by the particle density reaches the value of 1 GeV. This
observation is used to determine the energy dependence of the chemical
freeze-out parameters T_{ch} and mu_B^{ch} for beam energies varying between 1
and 200 A.GeV. The consequences of this energy dependence are studied for
various particle ratios. Predictions for particle ratios at beam energy 40
A.GeV are presented. The conditions for thermal freeze-out are also determined.
These correspond either to an energy density of 45 MeV/fm**3 or to a particle
density of 0.05/fm**3.
