RT info:eu-repo/semantics/article
T1 Updated determination of the molar gas constant R by acoustic measurements in argon at UVa-CEM.
A1 Segovia Puras, José Juan
A1 Lozano Martín, Daniel
A1 Martín González, María del Carmen
A1 Chamorro Camazón, César Rubén
A1 Villamañán Olfos, Miguel Ángel
A1 Pérez, Eduardo
A1 García Izquierdo, Carmen
A1 Campo, Dolores del
K1 Termodinámica
K1 Molar gas constant
K1 Triaxial ellipsoid resonator
K1 Kelvin
K1 Microwave resonance
K1 Speed of sound
K1 Acoustic resonance
AB A new determination of the molar gas constant was performed from measurements of the speed of sound in argon at the triple point of water and extrapolation to zero pressure. A new resonant cavity was used. This is a triaxial ellipsoid whose walls are gold-coated steel and which is divided into two identical halves that are bolted and sealed with an O-ring. Microwave and electroacoustic traducers are located in the northern and southern parts of the cavity, respectively, so that measurements of microwave and acoustic frequencies are carried out in the same experiment. Measurements were taken at pressures from 600 kPa to 60 kPa and at 273.16 K. The internal equivalent radius of the cavity was accurately determined by microwave measurements and the first four radial symmetric acoustic modes were simultaneously measured and used to calculate the speed of sound. The improvements made using the new cavity have reduced by half the main contributions to the uncertainty due to the radius determination using microwave measurements which amounts to 4.7 parts in 106 and the acoustic measurements, 4.4 parts in 106, where the main contribution (3.7 parts in 106) is the relative excess half-widths associated with the limit of our acoustic model, compared with our previous measurements. As a result of all the improvements with the new cavity and the measurements performed, we determined the molar gas constant R = (8.314449  0.000056) J·K-1·mol-1 which corresponds to a relative standard uncertainty of 6.7 parts in 106. The value reported in this paper lies -1.3 parts in 106 below the recommended value of CODATA 2014, although still within the range consistent with it.
PB IOP PUBLISHING
SN 1681-7575
YR 2017
FD 2017
LK http://uvadoc.uva.es/handle/10324/29085
UL http://uvadoc.uva.es/handle/10324/29085
LA eng
NO Metrologia 54 (2017) 663-673
NO Producción Científica
DS UVaDOC
RD 20-sep-2024