Discrepancies in turbidity measurements in the ionic binary mixture triethyl n-hexyl ammonium triethyl n-hexyl boride in diphenyl ether

Abstract

We have repeated and extended turbidity measurements on a new sample of the ionic mixture triethyl n-hexyl ammonium triethyl n-hexyl boride (N2226B2226) in diphenyl ether in a temperature range above its consolute point. Previous measurements on this system by some of us indicated mean-field critical behavior over the range of reduced temperatures 10−4<t<10−1. Our new measurements do not reproduce those reported before. The transmission of the new sample is substantially lower, and the turbidities up to a factor of 3 higher than those of the sample used in the previous work. The correlation-length amplitude is approximately 40% larger than that found for the previous sample. Unlike the earlier results, the new data do not display a substantial range of mean-field critical behavior. In our investigation of this irreproducibility, we have carefully reviewed the earlier experiment, and we report here an effect not previously noted: a time dependence of the turbidity of the earlier sample. It is likely that the discrepancy is due to impurity effects, but we do not understand their origin.

Phase diagram of charged dumbbells: A random phase approximation approach

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A Short History of Phase Transitions in Ionic Fluids

“…However, later turbidity measurements of the Pitzer-system indicated a flaw in the previous measurements of this system: Wiegand noted a changing of the critical temperature during the measurements, which leads to false determination of the critical exponents [74]. Measurements on carefully equilibrated samples consistently yielded Ising behavior for the turbidity, the scattering intensity, the phase diagram [75] and the viscosity [76].…”

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“…For a symmetric 1:1 electrolyte system, for example, recent experiments [1,2,3,4,5] and simulations [6,7,8,9, 10] strongly support three-dimensional Ising-like criticality as the asymptotic behavior. One of the most basic and successful models of ionic fluids is the restricted primitive model (RPM), in which the ions are viewed as equisized hard spheres carrying positive and negative charges of the same magnitude.…”