The thermodynamic behavior of mixtures R23/R744 and R41/R344 at saturation state was analysed. It was established that the difference of temperatures of saturated vapor and liquid on isobars for four values of composition not exceed 2 K. The dependences of these temperatures’ difference from pressure and temperature are presented in intervals from 0,1 up to 5,5 MPa and from 185 to 310 К. The characteristics of cycle of one-step refrigerating machine using mentioned mixtures as working media were estimated.