NIST logo

Publication Citation: Apparatus for Wide-Ranging, High-Accuracy Fluid p-ρ-T Measurements Based on a Compact Two-Sinker Densimeter

NIST Authors in Bold

Author(s): Mark O. McLinden; Cornelia Losch-Will;
Title: Apparatus for Wide-Ranging, High-Accuracy Fluid p-ρ-T Measurements Based on a Compact Two-Sinker Densimeter
Published: September 28, 2006
Abstract: An apparatus for high-accuracy fluid p-ρ-T measurements over wide ranges of temperature, pressure, and density (90 to 520 K; 0 to 40 MPa; 5 to 1700 kg/m3) is described. The densimeter is based on the Archimedes (buoyancy) principle and is a two-sinker system incorporating a magnetic suspension coupling. The density is obtained directly, without the need for calibration fluids. The complete apparatus, including the thermostat, pressure and temperature measuring systems, auxiliary systems, and computer control, is described. The determination of the sinker volumes and calibrations of the measuring systems are detailed. The traceability to national standards and fundamental SI quantities is emphasized. The uncertainty (k = 2) in density is {plus or minus}(0.0025 % + 0.0006 kg/m3) at 293 K and 0.1 MPa. The uncertainty increases to {plus or minus}(0.015 % + 0.001 kg/m3) at the upper and lower temperature limits of the apparatus and a pressure of 40 MPa, primarily due to increased uncertainties in the sinker volumes. The uncertainty in temperature is {plus or minus} 0.004 K and that in pressure ranges from {plus or minus} 0.005 % to 0.05 %. Results for high-purity nitrogen and helium demonstrate the performance of the densimeter and confirm the stated uncertainties. New data are presented for a high-density fluoroether; these measurements demonstrate the capabilities for liquids.
Citation: Journal of Chemical Thermodynamics
Volume: 39
Pages: pp. 507 - 530
Keywords: 2-trifluoromethyl-3-ethoxydodecafluorohexane;densimeter;experimental measurements;helium;nitrogen;pressure-density-temperature behavior;thermodynamic properties;two-sinker densimeter;virial coefficients
Research Areas: Thermophysics
PDF version: PDF Document Click here to retrieve PDF version of paper (1MB)