| For
the development of reliable equations
of state for technically and scientifically important
fluids, in particular accurate pρT measurements
of these fluids are required. For the experimental determination
of these basic properties several new accurate densimeters
have been developed and built up by our group since about
1980. Since putting these densimeters into operation they
are systematically used for the accurate measurements of selected
fluids.
pρT
measurements with the two-sinker densimeter
Using
the two-sinker
densimeter many important pure fluids have been comprehesively
measured up to now, namely methane [32,
33,
38,
57,
125/appendix],
carbon dioxide [46,
47,
62,
97],
argon [69,
70],
ethylene [90,
91],
nitrogen [39,
98,
99],
sulphur hexafluoride [59,
131,
132],
and ethane [134,
135].
These fluids were measured in the entire pρT region
covered by the densimeter (saturated-liquid densities, saturated
vapour-densities, and vapour pressures from the triple-point
temperature to the critical temperature; homogeneous gas and
liquid region, including the critical region, from the triple-point
temperature to T = 340 K and for pressures from 0.001
MPa to 12 MPa). Moreover, two refrigerants were measured in
selected regions of the pρT surface [58]
. Recently, the pρT properties of propane, propylene,
n-butane, and isobutane were measured. The total uncertainty
of the measurements in density is ≤0.01% to ≤0.02%
for the most regions of the fluid state.
A typical example is presented by the keyword pρT
measuremens of the two-sinker densimeter using nitrogen as
an example.
pρT
measurements with the single-sinker densimeter
Using
the single-sinker
densimeter many important pure fluids have been measured
up to now, namely argon [109],
nitrogen [109],
methane [125],
carbon dioxide [125],
ethylene [137],
ethane [137],
and sulphur hexafluoride [137].
These fluids were measured in the entire pρT region
covered by the densimeter (homogeneous gas and liquid region
in the temperature range from 233 K to 523 K at pressures
up to 30 MPa). Moreover, propane were measured in selected
regions of the pρT surface. The total uncertainty
of the measurements in density is ≤0.02% for most regions
of the fluid state except for low gas densities below about
40 kg/m3.
A typical example is presented by the keyword
pρT measurements of the single-sinker densimeter
using ethane as an example.
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