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This paper will describe the screening and development of absorbents for HFC-134a in the chemical/mechanical heat pump. The absorbents must have low volatility, low melting point, high solubility for HFC-134a vapor, high heat of mixing with HFC-134a, suitable vapor pressure/temperature concentration characteristics when mixed with HFC-134a, low toxicity, low flammability, and thermal stability. A screening procedure was used to select approximately 15 absorbents for experimental evaluation. Measurement of the key physical and thermodynamic properties of the absorbent/HFC-134a mixtures, such as vapor pressure/temperature/concentration properties, materials compatibility, and thermal stability, is described. From these measurements, activity coefficients, enthalpy of mixing, and entropy of mixing of the liquid solution were determined.