A Two-Sinker Densimeter for Accurate Measurements of the Density of Natural Gases at Standard Conditions

A special reference densimeter has been developed for accurate measurements of densities of natural gases and multicomponent gas mixtures at standard conditions of temperature and pressure (T _s = 273.15 K and p _s = 0.101325 MPa). The densimeter covers the range from 0.7 kg · m^?3 to 1.3 kg · m^?3; the total measurement uncertainty in density is 0.020 % (95 % level of confidence). The measurement principle used is the two-sinker method, which is based on the Archimedes buoyancy principle. The certified calibration laboratory of E.ON Ruhrgas AG, Germany, uses this densimeter to verify the standard densities of certified calibration gases (binary and multicomponent gas mixtures). Moreover, the densimeter is used to determine the compositions of commercially available binary gas mixtures with a small uncertainty of (0.01–0.03) mol%.