When two fluid phases are near a critical point, one of them will be excluded from contact with any third phase that happens to present by wetting film the other phase. A simple and quite general strategy may used induce transition complete incomplete is add new component chosen drive away their point. This illustrated for methanol-cyclohexane mixtures.

We review the principles, techniques and results from primary acoustic gas thermometry (AGT). Since establishment of ITS-90, International Temperature Scale 1990, spherical quasi-spherical cavity resonators have been used to realize AGT in temperature range 7 K 552 K. Throughout sub-range 90 < T 384 K, at least two laboratories measured (T − T90). (Here is thermodynamic T90 on ITS-90.) With a minor exception, resulting values T90) are mutually consistent within 3 × 10−6 T. These measurements...

For helium, the accuracy of calculated transport properties and virial coefficients based on an accurate ab initio potential now exceeds that best measurements. The results should be used to calibrate measuring apparatus.

The presence of a gravitational field leads to both practical and fundamental limits the resolution in critical phenomena experiments fluids near gas-liquid point. We present equations that yield estimates limitations variety for large number as function magnitude field. Various strategies improving such are discussed, including procedures remove fluid from thermodynamic equilibrium (e.g., stirring). A comparison is made between earth-bound those at microgravitational levels may become...

We report a new determination of the Universal Gas Constant R: (8.314471 ±0.OOOOI4)J.mol-1K-1 • The uncertainty in value is 1.7 ppm (standard error), factor 5 smaller than best previous value.The gas constant was determined from measurements speed sound argon as function pressure at temperature triple point water.The measured with spherical resonator whose volume by weighing mercury required to fill it tem-perature tri~le point.The molar mass comparing standard sample accurately known...

We report a new value for the universal gas constant $R:8.314471\ifmmode\pm\else\textpm\fi{}0.000014$ J ${\mathrm{mol}}^{\ensuremath{-}1}$ ${\mathrm{K}}^{\ensuremath{-}1}$. The standard error of $R$ has been reduced by factor 5, to 1.7 ppm. was determined from speed sound in argon contained within thick, spherical shell at temperature triple point water ${T}_{t}$. volume measured our weighing mercury required fill it molar mass relative that with accurately known chemical and isotopic...

The liquid-vapor transition in a pure fluid and the liquid-liquid partially miscible liquid mixture are examples of phase transitions that have critical points. These systems exhibit striking macroscopic phe:. nomena near their Thermodynamic fluctuations within single extend over larger regions space become increasingly long-lived as point is approached. For example, liquid­ vapor point, liquid-like vapor-like large enough to scatter significant amounts light. Thus, fluids which transparent...

Data for the surface tension of pure fluids near critical points and interfacial between coexisting liquid phases binary mixtures consolute are reviewed using recent theoretical values exponents concept two-scale-factor universality [D. Stauffer, M. Ferer, Wortis, Phys. Rev. Lett. 29\ensuremath{\rightarrow}, 345 (1972)]. The data used to estimate universal amplitude ratios relating ${\ensuremath{\sigma}}_{0}$ specific-heat divergence correlation length ${T}_{c}$. a wide variety fluid systems...

Gas-filled spherical resonators are excellent tools for routine measurement of thermophysical properties. The radially symmetric gas resonances nondegenerate and have high Q’s (typically 2000–10 000). Thus they can be used with very simple instrumentation to measure the speed sound in a an accuracy 0.02%. We made detailed study prototype resonator filled argon (0.1–1.0 MPa) at 300 K, objective discovering those phenomena which must understood use gas-filled thermodynamic temperature...

We report precise optical measurements of the equations state Xe, S${\mathrm{F}}_{6}$, and C${\mathrm{O}}_{2}$ very near their critical points ($\frac{|T\ensuremath{-}{T}_{c}|}{{T}_{c}}&lt;5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$). find that exponents these fluids in this region are close to calculated from three-dimensional Ising model.

Recent quantum mechanical calculations of the interaction energy pairs helium atoms are accurate and some include reliable estimates their uncertainty.We combined these ab initio results with earlier published to obtain a helium-helium interatomic potential that includes relativistic retardation effects over all ranges interaction.From this potential, we calculated thermophysical properties helium, i.e., second virial coefficients, dilute-gas viscosities, dilutegas thermal conductivities 3...

We used a quasi-spherical cavity as an acoustic and microwave resonator to measure the thermodynamic temperatures, T, of triple points equilibrium hydrogen, neon, argon mercury difference T − T90, in range 7 K 273 K. (T90 is temperature on International Temperature Scale 1990 (ITS-90).) In 24.5 K, our preliminary values T90 agree with recent results from dielectric-constant gas thermometry achieve uncertainties that are comparable or smaller than those achievable using interpolating constant...

Using a quasispherical, microwave cavity resonator, we measured the refractive index of helium to deduce its molar polarizability A(epsilon) in limit zero density. We obtained (A(epsilon,meas) - A(epsilon,theory))/A(epsilon) = (-1.8 +/- 9.1) x 10(-6), where standard uncertainty (9.1 ppm) is factor 3.3 smaller than that best previous measurement. If theoretical value accepted, these data determine for Boltzmann constant only 1.8 9.1 ppm larger accepted value. Our techniques will enable...

We have measured the viscosity of four binary mixtures near their consolute points: (1) methanol+cyclohexane, (2) isobutyric acid+water, (3) nitroethane+3-methylpentane, and (4) 2-butoxyethanol+water. The data are consistent with power-law divergence: η∼‖T−Tc‖−y, an apparent exponent in range 0.0404&amp;lt;y&amp;lt;0.0444. Recent theoretical estimates for y 0.032, which is outside experimental range. value independent whether critical point upper or a lower approach toward Tc at constant...

We have measured the specific heat at constant volume (${C}_{v}$) of ${\mathrm{He}}^{4}$ near its critical temperature (${T}_{c}$) and density (${\ensuremath{\rho}}_{c}$). Tabulated data are given along seven isochores with densities in range $\ensuremath{-}0.10&lt;\ensuremath{\Delta}\ensuremath{\rho}&lt;+0.15$, where $\ensuremath{\Delta}\ensuremath{\rho}=\frac{(\ensuremath{\rho}\ensuremath{-}{\ensuremath{\rho}}_{c})}{{\ensuremath{\rho}}_{c}}$, temperatures...

In certain binary solutions the lower of two liquid phases forms a layer which intrudes between upper phase and vapor. The intruding layer's thickness (measured by ellipsometry) was 70 400 \AA{}. It varied approximately as ${L}^{\ensuremath{-}\frac{1}{3}}$ where $L$ is height spanned phase. This behavior predicted de Gennes using idea that long-ranged part intermolecular potential governs thickness. Deviations from occur near consolute points.

The SI unit of temperature will soon be redefined in terms a fixed value the Boltzmann constant k derived from an ensemble measurements worldwide. We report on new determination using acoustic thermometry helium-4 gas 3 l volume quasi-spherical resonator. method is based accurate and microwave resonances to measure speed sound at different pressures. find for universal R = 8.314 4614(50) J·mol−1·K−1. Using current best available Avogadro constant, we obtain 1.380 648 78(83) × 10−23 J·K−1...

The principles and techniques of primary refractive-index gas thermometry (RIGT) are reviewed. Absolute RIGT using microwave measurements helium-filled quasispherical resonators has been implemented at the temperatures triple points neon, oxygen, argon water, with relative standard uncertainties ranging from 9.1 × 10-6 to 3.5 10-5. Researchers now also argon-filled cylindrical for near ambient temperature, between 3.8 10-5 4.6 10-5, conducting on isobars low temperatures. optical frequencies...

Recent advances regarding the interplay between ab initio calculations and metrology are reviewed, with particular emphasis on gas-based techniques used for temperature pressure measurements. Since roughly 2010, several thermophysical quantities – in particular, virial transport coefficients can be computed from first principles without uncontrolled approximations rigorously propagated uncertainties. In case of helium, computational results have accuracies that exceed best experimental data...

The densities of the coexisting phases and capillary length have been measured to obtain interfacial tension (σ) near consolute temperatures Tc three binary liquid mixtures: triethylamine+water, triethylamine+heavy water, methanol+cyclohexane. Our data are combined with from literature test predictions for temperature-independent ‘‘universal’’ ratios: U+1=σ(ξ+)2/(kBTc) Y(±)=σ(αt2C±s/kB) −2/3/(kBT0). [Here ξ+ is correlation length, C±s singular part heat capacity per unit volume, α=0.11...

The speed of sound in gaseous 1,1,1,2-tetrafluoroethane (R134a) has been obtained between 233.16 and 340 K from measurements the frequency radial acoustic resonances a gas-filled spherical cavity. Perfect-gas heat capacities second third virial coefficients have calculated results. are used to estimate density B(T) C(T) an effective square-well potential. estimates consistent with deduced high-quality equation-of-state measurements; those for slightly inconsistent. apparatus its calibration...

Abstract The thermodynamic properties of vapor‐liquid equilibrium (VLE) states near the critical locus mixtures are correlated in very close analogy with techniques used to correlate pure fluids a point. only mixture parameters correlation values pressure, volume, temperature, and mole fraction ( PVTx ) along physical locus. We illustrate power present approach by correlating rather extensive data that exist loci binary mixtures: CO 2 C H 6 , SF 3 8 C 18 . Nearly all within 10% temperature...