Experimental determination of nitrogen density at high pressures and temperatures

The density of nitrogen was experimentally determined at pressures of 3-8 kilobar in the temperature range 400-1800 K with the aid of a special apparatus featuring an internal heat source. Gas convection was eliminated by filling the whole free space inside the apparatus with aluminum nitride of 60% porosity. Nitrogen density was determined by a variant of the displacement method of Tsiklis and Poliakov (1967). Two experiments were conducted with two different quantities of gas in the piezometer, but in one case an insert was placed in the device. After heating, the dependence of gas pressure on temperature was recorded, and the two curves were plotted in a pressure-temperature diagram. The coordinates of the point of intersection of the two curves determined the pressure and temperature values to which the density corresponds, equal to the ratio of the mass of gas displaced by the insert to the volume it occupies under the experimental conditions.