Ionic fluids

Pitzer K S 1995 Ionic fluids near-critical and related properties J. Phys. Chem. 99 13 070... 

Fisher M and Levin Y 1993 Criticality in ionic fluids Debye Huckel Theory, Bjerrum and beyond Phys. Rev. Lett. 71 3826... 

Fisher M 1996 The nature of criticality in ionic fluids J. Phys. Condens. Matter. 8 9103... 

Stell G 1995 Criticality and phase transitions in ionic fluids J. Stat. Phys. 78 197... 

Stell G 1999 New results on some ionic fluid problems, new approaches to problems in liquid state theory Proc. NATO Advanced Study Institute (Patte Marina, Messina, Italy 1998) ed C Caccamo, J P Hansen and G Stell (Dordrecht Kluwer)... 

Larsen B, Rasaiah J C and Stell G 1977 Thermodynamic perturbation theory for multipolar and ionic fluids Mol. Phys. 33 987... 

This approximation gives excellent results for the behavior of ionic fluids at charged surfaces [114,115]. 

It has been proposed to define a reduced temperature Tr for a solution of a single electrolyte as the ratio of kgT to the work required to separate a contact +- ion pair, and the reduced density pr as the fraction of the space occupied by the ions. (M+ ) The principal feature on the Tr,pr corresponding states diagram is a coexistence curve for two phases, with an upper critical point as for the liquid-vapor equilibrium of a simple fluid, but with a markedly lower reduced temperature at the critical point than for a simple fluid (with the corresponding definition of the reduced temperature, i.e. the ratio of kjjT to the work required to separate a van der Waals pair.) In the case of a plasma, an ionic fluid without a solvent, the coexistence curve is for the liquid-vapor equilibrium, while for solutions it corresponds to two solution phases of different concentrations in equilibrium. Some non-aqueous solutions are known which do unmix to form two liquid phases of slightly different concentrations. While no examples in aqueous solution are known, the corresponding... 

Maase, M. Massonne, K. Halbritter, K. et al. Method for the separation of acids from chemical reaction mixtures by means of ionic fluids. World Patent WO 03, 062171 (2003). 

Much of the popular reference to ionic fluids seems to be focused on the green chemical use of these remarkable substances as more ecologically and environmentally acceptable solvents in analytical procedures. We are a long way from any evidence that every possible use of organic solvents in analytical procedures has an ionic fluid analog. Only time will tell. 

Dense ionic fluids are not all that new if one examines the many applications of molten salt use in chemistry to date. A good deal of the work is in electrochemistry where the relatively high temperatures are less of a limitation but the relation between low-temperature molten salts and ionic fluids certainly exists. It would be wise neither to completely depend on nor to completely ignore all that has been learned with molten salts and molten salt chemistry. Some highly reactive, easily oxidized metals are readily purified in molten salt solvent systems without the problems with oxygen or the decomposition of water with release of hydrogen. 

How will the microscopic properties of ionic fluids complicate the application of these remarkable substances to new kinds of analysis If they are used... 

The distribution of the electric potential in the ionic fluid surrounding the particles is described by the following b.v.p. in TZ2 ... 

Here, p is the pressure and p is the space charge density, which for the equilibrium ionic fluid under consideration assumes the form... 

Finally, some simple estimates will be presented for the three-dimensional electrolyte concentration and electric potential fields resulting from concentration polarization in a diffusion layer adjacent to a spatially inhomogeneous ion-selective interface (membrane). It will be shown that the appropriate fields are incompatible with mechanical equilibrium in an ionic fluid, so that a related (nongravitational) convection is expected to arise at an inhomogeneous ion-exchange membrane upon the passage of an electric current. 

Preliminaries. This chapter is concerned with some aspects of the nonequilibrium space charge in a motionless ionic fluid. (Electro-osmosis as a particular instance of electro-convection is treated in the next chapter.)... 

This chapter deals with critical phenomena in simple ionic fluids. Prototypical ionic fluids, in the sense considered here, are molten salts and electrolyte solutions. Ionic states occur, however, in many other systems as well we quote, for example, metallic fluids or solutions of complex particles such as charged macromolecules, colloids, or micelles. Although for simple atomic and molecular fluids thermodynamic anomalies near critical points have been extensively studied for a century now [1], for a long time the work on ionic fluids remained scarce [2, 3]. Reviewing the rudimentary information available in 1990, Pitzer [4] noted fundamental differences in critical behavior between ionic and nonionic fluids. 

The organization of this review is as follows In Section II we describe the theoretical and experimental background of the field. Section HI reviews experimental work on the criticality of ionic fluids. Section IV presents the basic theoretical methods for describing ionic phase transitions at the mean-field level. Results obtained by these techniques are reviewed in Section V. Section VI reviews the theoretical work concerned with the nature of the critical point. The review closes in Section VII with a brief summary and outlook. 

The bare Coulombic interaction (p = 1) and interactions of charges with rotating dipoles (p = 4) do not fall into this class, and it has been argued for a long time [30] that in this case one expects analytical ( classical ) behavior. This implies that the system can be described by a mean-field Hamiltonian, in which the interaction of a particle is ascribed to the mean field of all other particles, thus ignoring local fluctuations [10]. In real ionic fluids the... 

A. Liquid-Vapor Transitions in One-Component Ionic Fluids... 

Guillot s EOS T = 0.058 and p S 0.08. As discussed later in Section V.A, the best available MC results for the charge- and size-symmetrical hard-sphere ionic fluid yield [52, 53]... 

Nevertheless, Buback and Franck s results indicate that ionic fluids may differ appreciably in their effective critical behavior from nonionic fluids. 

BiCl3 is, however, little conducting in the liquid phase, and it resembles nonionic rather than ionic fluids. This may warn that specific interactions may destroy the peculiar effects of ionic criticality. Likewise, water (Tc = 647 K) shows Ising behavior [61]. At the critical point, autoprotolysis of water is enhanced by three orders of magnitude relative to ambient conditions [62]. 

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