Determination of the thermodynamic temperature between 236 K and 430 K from speed of sound measurements in helium

We report speed of sound measurements in helium at 273.16 K and at eight temperatures in the range between 236 K and 430 K. These results determine the difference (T  −  T 90) between the thermodynamic temperature T and its approximation T 90 by the International Temperature Scale of 1990 (ITS-90). The uncertainty of our measurements of (T  −  T 90) spans between a minimum of 0.25 mK near 247 K and a maximum of 0.89 mK at the freezing point of indium (429.75 K) with comparable contributions from the uncertainty of our acoustic determination of T and from the uncertainty of our laboratory realization of ITS-90. On the overlapping temperature ranges these results are consistent with other recent acoustic determinations of (T  −  T 90). We also present evidence that (T  −  T 90) can be determined with comparably small uncertainties by the alternative, time-saving procedure of measuring the speed-of-sound in helium using only a single, judiciously-chosen, pressure on each isotherm

Quantum-based realizations of the pascal: status and progress of the EMPIR-project: quantumpascal

The QuantumPascal (QP) project combines the capabilities of 12 European institutions to enable traceable pressure measurements utilizing quantum-based methods that evaluate the number density instead of force per area to target the wide pressure range between 1 Pa and 3 MPa. This article summarizes the goals and results since the project start in June 201

The role of vapour pressure in multibubble sonoluminescence from organic solvents

The action of high intensity cavitation on several liquid halocarbons (C2Cl4 CCl4, CHCl3, C2H2Br4) and other organic solvents (acetone, benzene and their mixtures) was investigated by recording multibubble sonoluminescence UV-Vis spectra over the temperature range between 246 and 298 K. The temperature induced variation of some thermophysical properties of the solvents Favours the interpretations of their role in determining the salient characteristics of the recorded spectra. We observed that high volatility does not necessarily quench sonoluminescence emission and that argon flow plays a key role in the appearance of radical emission lines. While for each investigated substance the intensity of C-2(center dot) emission lines was clearly correlated to temperature, a comparative test between different halocarbons did not show a clear correlation with vapour pressure. Following recently reported results which evidenced the formation of dynamically differentiated populations of emitting bubbles in sulphuric acid, we performed MBSL experiments in liquid mixtures of halocarbons and sulphuric acid to investigate the correlation between the production of emitting species and the halocarbon volatilit

Acoustic and microwave method in spherical cavities for the determination of the thermophysical properties of gaseous mixtures

The experimental methods and the underlying theory for the accurate determination of the speed of sound in gases with spherical cavities have been substantially improved during the past two decades aiming at an accurate acoustic determination of the Boltzmann constant. Here, we discuss the possible use of these methods and instrumentation for the determination of the speed of sound and other thermophysical properties of binary monoatomic gas mixtures. These properties, which include the diusion and thermo-diusion coecients, are of interest for several applications, such as thermoacoustic engines and acoustic methods for the determination of the composition of ssion gases in nuclear fuel rods. Interestingly, the extremely high accuracy achievable with these experiments over a wide range of temperatures and pressures may help to discriminate among contrasting theories of acoustic propagation in gas mixtures and the competing validity of the methods commonly used to predict the transport properties of mixture