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The Kamlet−Taft parameters describing the dipolarity-polarizability, π*, and hydrogen bond acceptor ability, β, 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 π* and β were calculated for each of the solvents as a function of the solvent density. Trends in π* values were related to the degree of fluorination about the ethane molecule, while the average β values for all solvents were negative and were interpreted as an inability on the solvents part to act as hydrogen bond acceptors.