The Sound Velocity in Ideal Liquid Mixtures from Thermal Volume Fluctuations

Abstract

The selection of the correct mixing rule for sound velocity in ideal liquid mixtures determines the interpretation of the sound velocity in real mixtures. This is especially important for the determination of apparent properties of solutes, such as their apparent compressibility. There are different approaches reported in the literature, and this article presents a new derivation of the mixing rule based on statistical mechanics. It is shown that the correlation of volume fluctuations between adjacent components has a crucial influence on the ideal mixing rule.

Thermodynamic and transport properties of (1,2-ethanediol+1-nonanol) at temperatures from (298.15 to 313.15)K

“…Moreover, an inspection of the literature reveals that there is no generally accepted approach describing the speed of sound of ideal mixtures. The lack of a general agreement concerning the ideal mixing rules in the case of c has been quite recently discussed in detail by Douhéret et al in a review article [34] (this subject has been also taken up by Gliń ski [35] and Pfeiffer and Heremans [36]). The calculated c D values have been also compared with the c DNB values (c DNB = c À c id ) obtained on the basis of Natta-Baccaredda model [37].…”

Thermotropic phase behaviour of the pseudobinary mixtures of DPPC/C12E5 and DMPC/C12E5 determined by differential scanning calorimetry and ultrasonic velocimetry

“…This additivity is a consequence of the dynamic behaviour of molecules in liquids and arises from the correlation of thermal volume fluctuations of adjacent molecules (Pfeiffer and Heremans, 2005). There is reason to assume that this equation can serve as a more appropriate reference state for describing the sound velocity of mixtures than Eq.…”

Protein dynamics: hydration and cavities

“…Unfortunately no computer simulations are available which would allow an estimate of the contributions of hydration and cavities from temperature changes. The additivity of volumes, compressibility and thermal expansion may also be viewed from a statistical mechanical treatment of the volume fluctuations (42). When the coupling between the fluctuations of the solvent and the protein is strong, as may be expected in hydrogen-bonded systems, then the additivity rule does not apply.…”