This paper presents measurements of vapor pressures from 250 K to 450 K, liquid densities from 180 K to 370 K at pressures up to 70 MPa, vapor densities at 400 K at pressures up to 1 MPa, and the critical temperature for 1,1-dichloro-1-fluoroethane (R-141b). The derived second and third virial coefficients at 400 K are -459.5 x 10(-6) m(3) . mol(-1) and 1.93x10(-8)m(6) . mol(-2). Extrapolating the observed vapor pressures to the measured critical temperature (477.5+/-0.4)K provides a critical pressure of(4.194+/-0.002) MPa. Using these values with the law of rectilinear diameters indicates a critical density of (3921+/-6) mol . m(-3) Correlations provide values which agree with the measured values for liquid densities within +/-0.1% and vapor pressures within +/-0.05%. All uncertainties reported in the paper are 3 sigma.