Vapor pressures and liquid densities for ammonium chloride (NH4Cl) + ammonia (NH3) mixtures were measured over a wide range of temperatures and concentrations. Vapor pressures of the NH4Cl + NH3 mixtures were measured at temperatures ranging from (303.12 to 373.16) K and concentrations ranging up to 50.74 wt % of NH4Cl. Vapor pressure was measured with a pressure transducer. The experimental values were correlated with Antoine's equation. Liquid densities of the NH4Cl + NH3 mixtures were measured at temperatures ranging from (303.15 to 373.15) K, pressure ranging from (10.0 to 30.0) MPa, and concentrations ranging up to 50.68 wt % of NH4Cl. Liquid densities were measured with a piezometer. The experimental values were correlated with a Tait-form equation.