  By means of standard and histogram Monte Carlo simulations, we investigate
the critical and compensation behaviour of a ternary mixed spin alloy of the
type $AB_pC_{1-p}$ on a cubic lattice. We focus on the case with the parameters
corresponding to the Prussian blue analog $({\rm Ni}^{\rm II}_p {\rm Mn}^{\rm
II}_{1-p})_{1.5}[{\rm Cr^{III}(CN)}_6] \cdot n {\rm H_2O}$ and confront our
findings with those obtained by some approximative approaches and the
experiments.
