Densities of aqueous solutions of NH4Cl at molalities ranging from 0.1 mol . kg(-1) to 6.0 mol . kg(-1), temperatures from 298.15 K to 623 K, and pressures of 10 MPa and 28 MPa were measured using a vibrating tube how densitometer. Heat capacities of the above solutions at temperatures from 302 K to 623 K and a pressure of 28 MPa were measured using a flow heat-capacity calorimeter. The volumetric and calorimetric results for NH4Cl(aq) are in good agreement with the literature data at low temperatures. At high temperatures, observed volumes and heat capacities of NH4Cl(aq) are consistent with the assumption of strong electrolyte behavior, with only small effects from reactions to form NH3(aq), H+(aq), and HCl(aq), and from ion pairing of NH4+(aq) with Cl-(aq).