Study of a Binary Critical Mixture of 2,6‐Dimethyl Pyridine/Water: Measurements of Static and Dynamic Light Scattering and Specific Heat Near the Lower Critical Point

Abstract

Static and dynamic light scattering experiments are reported for the system 2,6‐dimethyl pyridine/water to determine the critical amplitude ζo of local concentration fluctuations and the critical amplitude Ωo of the characteristic frequency ΩD to scale ultrasound absorption data. It is found: ζo = (2.7 ± 0.2) · 10−8 cm and Ωo/π = 2.9 GHz. Measurements of the temperature dependence of specific heat capacity at constant pressure lead to a critical amplitude A = (0.183 ± 0.002) J g−1 K−1. The two scale factor universality is tested by combining the values of ζ0 and A as well as the values of ζ0 and τ*0 and B* (B*: critical amplitude of the coexistence curve, τ*0 critical amplitude of turbidity). The two ratios of the critical amplitudes calculated from the experimental data are higher by about 15% than the highest theoretical predicted value.

Critical behaviour of binary mixture of {xC6H5CN+(1−x)CH3(CH2)7CH3}: Measurements of coexistence curves, light scattering, and heat capacity

“…The value of X was predicted to be (0.01966 ± 0.00017) from an expansion of d = 3 [41], and (0.01880 ± 0.00008) from high-temperature series [2], respectively. Recent experimental determinations have found X to be in the range between 0.019 and 0.028 [28,30,34,36,39,[42][43][44]. Our measurements in the range (T À T c ) = (0 to 2.8) K gave the values of amplitude n 0 of the correlation length and amplitude A + of the heat capacity to be (0.287±0.005) nm and (0.01365 ± 0.00009) J Á K À1 Á cm À3 , respectively.…”

Drag coefficient of a rigid spherical particle in a near-critical binary fluid mixture, beyond the regime of the Gaussian model

“…The proportionality of ξ ∝ τ −ν with ν ≈ 0.627 is observed in the bulk of a binary fluid mixture with the critical composition when it is sufficiently close to the critical point. The Gaussian free-energy density, giving ξ ∝ τ −0.5 instead, appears to be valid when ξ is smaller than approximately 15 nm in the bulk of the mixture of 2,6-lutidine and water (Jungk, Belkoura & Woermann 1987). When the particle motion is studied in the Gaussian model Fujitani 2018), the correlation length is assumed to be homogeneous and much smaller than the minimum of l, i.e.…”

1H and 2H NMR Studies of Mixtures 2,6-Lutidine/Water Near the Lower Critical Solution Point

“…in the vicinity of the lower critical solution point (T c L ). This system has been chosen because precise measurements of the phase diagram and other critical data are available [11][12][13][14][15]. Moreover the critical anomalies of 'H NMR chemical shifts and linewidth in 2,6-lutidine/H 2 0 solutions have been reported [5].…”