Apparent molar volumes and apparent molar isentropic compressibilities of newly synthesized ammonium-based protic ionic liquid (PIL), namely diethylethanolammonium propionate, at T = (293.15 to 328.15) K and at atmospheric pressure were obtained from experimentally measured density and speed of sound data. Redlich-Mayer type of equation was used to calculate infinite dilution apparent molar volumes, V2 ∞, infinite dilution apparent molar isentropic compressibilities, Ks,2 ∞, and corresponding empirical parameters (Sv, Bv, Sk, and Bk). Positive magnitude of limiting volumetric slope Sv versus m1/2 for protic ionic liquid (PIL) + water binary solutions, suggests that PIL-water interactions are weak. Further, the temperature dependence of V2 ∞ values has also been evaluated. © 2015, Springer-Verlag Berlin Heidelberg.