Isochoric p-rho-T measurements on 1,1-difluoroethane (R152a) from 158 to 400 K and 1,1,1-trifluoroethane (R143a) from 166 to 400 K at pressures to 35MPa

The p-rho-T relationships have been measured for 1,1-difluoroethane (R152a) and 1,1,1-trifluoroethane (R143a) by an isochoric method with gravimetric determinations of the amount of substance. Temperatures ranged from 158 to 400 K for R152a and from 166 to 400 K for R143a, while pressures were up to 35 MPa. Measurements were conducted on compressed liquid samples. Determin ations of saturated liquid densities were made by extrapolating each isocho re to the vapor pressure, and determining the temperature and density at th e intersection. Published p-rho-T data are in good agreement with this stud y. For the p-rho-T apparatus, the uncertainty of the temperature is +/- 0.0 3 K, and for pressure it is +/-0.01% at p > 3 MPa and +/-0.05% at p < 3 MPa . The principal source of uncertainty is the cell volume (similar to 28.5 c m(3)), which has a standard uncertainty of +/-0.003 cm(3). When all compone nts of experimental uncertainty are considered, the expanded relative uncer tainty (with a coverage factor k=2 and thus a two-standard deviation estima te) of the density measurements is estimated to be +/-0.05%.