Densities and volumetric heat capacities for dilute solutions of N-methylpiperidine (N-MP, 0.2 mol·kg−1) and N-methylpiperidinium chloride (N-MPH+Cl−, 0.1 mol·kg−1) were measured relative to water at 0.1 MPa using a vibrating-tube densimeter, and at 0.4 MPa using a twin fixed-cell, power-compensation, differential temperature-scanning nano calorimeter, over the temperature ranges 283.15 K ≤ T ≤ 363.15 K and 283.15 K ≤ T ≤ 393.15 K, respectively. The resulting apparent molar volumes, Vϕ, and heat capacities, Cp,ϕ, were corrected for speciation effects using Young’s rule and extrapolated to infinite dilution using the Debye-Hückel limiting law, Yo ≈ Yϕ − AYIs1/2, to yield the standard partial molar properties, Yo, for N-MP(aq) and N-MPH+Cl−(aq). The standard partial molar volumes, Vo, and heat capacities, Cpo, were represented by a semi-empirical function of solvent density and temperature, Yo(ρw,T), the “density” model, which can be used to extrapolate these results, as well as other thermodynamic properties for the ionization of N-methylpiperidine, to higher temperatures.