The Density of Ammonia at High Pressures to 723 K and 950 MPa

High pressure-high temperature procedure and equipment is described to determine the specific volume of ammonia as a function of pressure and temperature. An autoclave consisting of a nickel-based superalloy and a suitable pressure-sensitive separator between ammonia and the pressure-transmitting fluid is used. Ten volume isotherms between 298 and 723 K and at pressures from 10 to 950 MPa have been determined. Previous literature data extend to 950 MPa but only up to 473 or to 723 K at pressures below 500 MPa. Polynomials with up to eleven terms are used to represent each experimental volume isotherm with a maximum average deviation of 0.16%. A table with smoothed density values is presented for the whole range of conditions. A comparison with data calculated earlier by Haar and Gallagher (1978) up to 500 MPa showed deviations between 0.06 and 1.1% with an average of 0.4%. The present isothermal volume data are reasonably well described by Tait equations. Parameters are given.