Results of (pressure, density, temperature) measurements on methane and on nitrogen in the temperature range from 273.15 K to 323.15 K at pressures up to 12 MPa using a new apparatus for accurate gas-density measurements

Measurement and correlation of the (p,ρ,T) relation of nitrogen. I. The homogeneous gas and liquid regions in the temperature range from 66 K to 340 K at pressures up to 12 MPa

“…With the exception of the measuring runs of Friedman, (25) Canfield et al, (26) and Crain and Sonntag (28) nearly all data points confirm each other within the experimental uncertainty of this work. In particular, the (p, r, T ) values of Pieperbeck et al, (34) Guo et al, (31) and Duschek et al (7) are in excellent agreement with the new values, mostly to within =5·10 −5 ·r =. (The apparatus used by Pieperbecket al, (34) and Guo et al, (34) is also a ''Two-Sinker-Densimeter'' which was designed by our group (34) especially for density measurements in the gas region; this apparatus is at the laboratories of Ruhrgas AG in Dorsten, Germany.…”

“…In particular, the (p, r, T ) values of Pieperbeck et al, (34) Guo et al, (31) and Duschek et al (7) are in excellent agreement with the new values, mostly to within =5·10 −5 ·r =. (The apparatus used by Pieperbecket al, (34) and Guo et al, (34) is also a ''Two-Sinker-Densimeter'' which was designed by our group (34) especially for density measurements in the gas region; this apparatus is at the laboratories of Ruhrgas AG in Dorsten, Germany. The measurements of Duschek et al (14) were carried out for special purposes 10 years ago.…”

“…(35) The grey area corresponds to the experimental uncertainty of the measurements in this work. Figure 5 shows comparisons with selected experimental results of other workers (14,(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) on three supercritical isotherms in the temperature range between 260 K and 325 K. The diagrams have an extremely large resolution of 23·10 −4 ·r due to the outstanding data situation in this special temperature range close to the ambient temperature. With the exception of the measuring runs of Friedman, (25) Canfield et al, (26) and Crain and Sonntag (28) nearly all data points confirm each other within the experimental uncertainty of this work.…”

“…A detailed comparison of the new (p, r, T ) values with several selected measurements of other workers (14,(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) is presented on 12 representative isotherms outside the critical region in figures 2 to 5 (relative deviation in density) and on three isotherms in the critical region in figure 6 (relative deviation in pressure). The figures show the deviations between measured values and values calculated from a preliminary equation of state, which was established only for comparison purposes and was fitted only to the new measurements.…”

“…In addition to the experimental results, the figures also contain plots of values calculated from two equations of state; one was published in the IUPAC book on nitrogen (35) and the other in Jacobsen et al (36) The first temperature value given above each diagram corresponds to our measurements and the temperature range written in brackets covers the results of the other authors. A summary of the selected sets of measurements (14,(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34) together with their uncertainties is listed in table 3. In order to avoid overcrowding of the diagrams in the case of very comprehensive sets of measurements some of the measuring points have been omitted, however, without losing any essential information.…”