Results of pycnometer based experiments at INRIM to measure LNG density

A novel pycnometer and a cryogenics apparatus were designed and manufactured in support of the EMRP – ENG 03 “Metrology for LNG” to provide accurate density measurements of Liquid Natural Gas and synthetic natural gas mixtures in the liquid region. Densities of two Synthetic Natural Gas Mixtures have been determined in the temperature range 100 K and 111 K with pressures up to 6 bar (0,6 MPa). An unexpected change in composition of the samples affected the liquid density. Such effect could be due to adsorption in the Titanium surface of gas molecules and to evaporation of the mixture light components