Molten salts corresponding states

Thermodynamic data show that the stabilities of the caesium chloride-metal chloride complexes are greater than the corresponding sodium and potassium compounds, and the fluorides form complexes more readily than the chlorides, in the solid state. It would seem that the stabilities of these compounds would transfer into the liquid state. In fact, it has been possible to account for the heats of formation of molten salt mixtures by the assumption that molten complex salts contain complex as well as simple anions, so that the heat of formation of the liquid mixtures is the mole fraction weighted product of the pure components and the complex. For example, in the CsCl-ZrCLt system the heat of formation is given on each side of the complex compound composition, the mole fraction of the compound... 

The noncrystalline sohds described here are amorphous and metastable. This specific thermodynamic property is because they aU originate from the liquid state. The corresponding glassy or vitreous materials are not very common in solid-state chemistry, and only a limited number of molten salts or molten alloys have the characteristics necessary to produce glasses when cooling. 

Simulations of the RPM predict a phase transition for the RPM at low reduced temperature and low reduced density. It was difficult to localize because of the low figures of the critical data. By corresponding states arguments this critical point corresponds to the liquid/vapor transition of molten salts and to some liquid/liquid transitions in electrolyte solutions in solvents of low dielectric constant [23, 24],... 

The oxoacidity scale of molten salts at 800 °C is presented in Fig. 1.3.5. The oxoacidic properties of the chloride melts are stated to be close, whereas those of the bromide ones differ appreciably. As a rule, the bromides are more acidic than the corresponding chlorides. Similar to the single chloride melts, the molten iodides are of the same acidities, which are weaker that those of the chloride melts. Molten bromides are found to possess higher acidities in the chloride-bromide-iodide sequences for potassium and... 

Theories for the prediction of thermochemical properties of molten salts have been reviewed a number of times over the years [131-134]. The main approaches that have been used are hole theory [135-137], corresponding states theory [138-140], perturbation theories [114, 141], and the significant structure theory [142-144]. Empirical correlation expressions have also been developed for the various properties as dealt with in the appropriate sections below. 

The corresponding states theory was developed by Reiss, Mayer and Katz [138] to deal with molten salts. It employs the primitive model with a single distance parameter d (=2ri in Eq. 3.8) to which all the inter-ionic distances in the entire volume of the molten salt V are proportional = 4ijd for all ions I and J, whether 1 = J or 1 / J. Reduced thermodynamic quantities are then defined as ... 

Young and O Connell [140] presented a corresponding states correlation of alkali metal salt viscosities, from which a relationship with the molar volumes may be derived, which is, however, very much more complicated than Eq. (3.46). Janz et al. [258] subsequently extended this treatment to 1 2 and 2 1 molten salts. The resulting expressions are ... 

Another application of the corresponding states approach is that of Abe and Nagashima [259], who used the Tosi-Fumi [112] potential function to obtain the two parameters d = r+ + r for the distance and e for the potential energy. The resulting expression for the fluidity of a molten salts is ... 

Young RE, O Connell JP (1971) Empirical corresponding states correlatitm of densities and transport properties of 1-1 alkali metal molten salts. Ind Eng Chem Fund 10 418-423... 

Harada M, Masataka T, Tada Y (1983) Law of corresponding states of uniunivalent molten salts. Ind Eng Chem Fund 22 116-121... 

Janz GJ, Yamamura T, Hansen MD (1989) Corresponding- states data cmrelations and molten salts viscosities. Inti J Thermophys 10 159-171... 

Tada Y, HiraokaS, UemuraT, HaradaM (1958) Corresponding states correlation of transport properties of uniunivalent molten salts. Ind Eng Chem Res 27 1042-1049... 

Since the number of voids is probably increasing with temperature, the solubility of the gas is also expected to increase accordingly. Predictions of solubilities in molten salts based on the scaled particle theory and the theory of corresponding states were published by Lee and Johnson. ... 

Cadmium is a member of Group 12 (Zn, Cd, Hg) of the Periodic Table, having a filled d shell of electrons 4valence state of +2. In rare instances the +1 oxidation state may be produced in the form of dimeric Cd2+2 species [59458-73-0], eg, as dark red melts of Cd° dissolved in molten cadmium halides or as diamagnetic yellow solids such as (Cd2)2+ (AlCl [79110-87-5] (2). The Cd + species is unstable in water or other donor solvents, immediately disproportionating to Cd2+ and Cd. In general, cadmium compounds exhibit properties similar to the corresponding zinc compounds. Compounds and properties are listed in Table 1. Cadmium(TT) [22537 48-0] tends to favor tetrahedral coordination in its compounds, particularly in solution as complexes, eg, tetraamminecadmium(II) [18373-05-2], Cd(NH3)2+4. However, solid-state cadmium-containing oxide or halide materials frequently exhibit octahedral coordination at the Cd2+ ion, eg, the rock-salt structure found for CdO. 

The most widespread mistake is the assumption that thermally unstable substances exist in an unchanged state at elevated temperatures in nitrate melts, and processes such as dehydration and decarboxylation are not taken into account. This omission is partially reflected in the conclusion that there is no correlation between the pH of aqueous solutions of some salts (usually, phosphates) and the pO values of the corresponding solutions of these salts in molten KNO3. The reason for this is as follows. 

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