  We have studied thermodynamic properties of noninteracting gases in periodic
lattice potential at arbitrary integer fillings and compared them with that of
ideal homogeneous gases. Deriving explicit expressions for thermodynamic
quantities and performing exact numerical calculations we have found that the
dependence of e.g. entropy and energy on the temperature in the normal phase is
rather weak. In the Bose condensed phase their power dependence on the reduced
temperature is nearly linear, which is in contrast to that of ideal homogeneous
gases. We evaluated the discontinuity in the slope of the specific heat which
turned out to be approximately the same as that of the ideal homogeneous Bose
gas for filling factor $\nu=1$. With increasing $\nu$ it decreases as the
inverse of $\nu$. These results may serve as a checkpoint for various
experiments on optical lattices as well as theoretical studies of weakly
interacting Bose systems in periodic potentials being a starting point for
perturbative calculations.
