A modification of the Peng-Robinson equation of state (PR EOS) is described that has been used to calculate physical properties and phase equilibria for fluorinated hydrocarbons, HF, and mixtures containing these compounds. The key modifications are improved mixing rules for mixtures containing hydrofluorocarbons and an association model for HF that assumes a chemical equilibrium between HF monomers and hexamers. Equation-of-state parameters are presented for 21 pure compounds, including many halogenated compounds, ammonia, chlorine, hydrogen chloride, dimethyl ether, n-butane, and water. Generalized correlations are also presented that allow estimation of the EOS parameters for other compounds based on the measurement of liquid density and vapor pressure at a single temperature. Chemical association constants for HF and the PR EOS parameters for HF monomer and hexamer are also reported over the temperature range from -78 to 180 degrees C.