We make some predictions with respect to the critical parameters of Al, Cu and W( critical parameters of which lie in the phase domain still inaccessible for experiment) on the basis of the correspondence between the critical point and unit compressibility line (Zeno line) positions in the temperature-density plane using two new similarity relations. These ones rely on the fact that the Zeno line must be tangential to the extension of the liquid branch of the binodal at zero temperatures and correctly describe its low-temperature part. We show also that the compressibility factor at the critical point can not exceed 0.32 for the Lennard-Jones like systems. (c) 2008 Elsevier B. V. All rights reserved.