Sound speed data have been obtained for thirteen binary mixtures and four multicomponent mixtures of natural gas components using a cylindrical cavity.These data cover a temperature range from 250 to 350 K at pressures to 10 MPa.The uncertainty in the data is approximately 0.05 percent.The binary mixtures are primarily methane-rich, with ethane, nitrogen, carbon dioxide, or propane as the second component.The multicomponent mixtures are representative of commercially available compositions in the United States and Europe.The data were used to develop and test mathematical models for prediction of the sound speed of natural gas mixtures, within an average uncertainty of 0. 1 percent, over the ranges of pressure, temperature, and composition that encompass the major region of custody transfer for natural gas.

A torsional piezoelectric crystal viscometer for compressed gases and liquids at temperatures to 600 K and a pressures to 70 MPa has been developed. Several torsional crystals were prepared from swept (electrolyzed) quartz to obtain a good performance at high temperatures. Measurements of the bandwidth of the crystal resonance curve were automated using an impedance analyzer. The viscometer was tested on compressed gaseous argon and methane at temperatures to 500 K and at pressures to 50 MPa. The measurements differ from accurate wide-range correlating equations by less than 2%.

The state-of-the-art of radio-frequency current measurement is reviewed with emphasis on the most useful standards. In particular, thermocouple and electrodynamic ammeters are discussed in detail. Reference is made to photoammeters, air thermometer milliammeters, and other types of current-measuring apparatus, some of which deserve additional development. Extensive referencing is included for the ...