The liquid density, boiling point, critical temperature and critical density are investigated for R-161 (CH3CH2F, bp = -37.3 degrees C), CF3SCF3 (bp = -20.1 degrees C), and RE-218 (CF3OCF2CF3, bp = -23.7 degrees C); which are potential R-12 and R-22 alternatives. Since the range of applicability of chemicals may be improved by considering their mixtures, the vapor pressure of the mixtures; CH3CH2F/CF3SF5, CF3CH2F/CF3SF5, and CF3(CF2)(2)CH2F (R-338mccq)/isopentane; were also investigated. The critical mixing temperature of the CH3CH2F/CF3SF5 mixtures is above -30 degrees C which is greater than the normal boiling point of -40 degrees C. Therefore, these mixtures would have Limited application as R-12 and R-22 alternatives. The normal boiling point of the R-134a (CF3CH2F)/CF3SF5 mixtures at the azeotropic R-134a mole fraction, 0.60, is -30.0 degrees C. The critical mixing temperature of the latter mixtures is well below the boiling point and is not a factor in refrigeration applications. The CF3(CF2)(2)CH2F (R-338mccq)/isopentane mixtures have a normal boiling point of 15.1 degrees C and a critical mixing temperature of about -5 degrees C which may be acceptable for some applications as a R-11 alternative. (C) 1998 Elsevier Science B.V. All rights reserved.