The Kamlet-Taft parameters describing the dipolarity-polarizability, pi*, and hydrogen bond acceptor ability, beta, for ethane and six fluorinated ethane solvents in the sub-and supercritical region of the phase diagram were measured using solvatochromic probe molecules. The measured ultraviolet electronic transitions of the solvatochromic probes in a given solvent were fitted to third-order polynomials in solvent density for all isotherms investigated. The values of pi* and beta were calculated for each of the solvents as a function of the solvent density. Trends in pi* values were related to the degree of fluorination about the ethane molecule, while the average beta values for all solvents were negative and were interpreted as an inability on the solvents part to act as hydrogen bond accepters.