Solid solution regular

Ihe present paper is intended to review the most important literature in this field and to extend the theory from the widely accepted ideal solid solutions to the more general models of regular solid solutions ( 5), with and without ordering (6 ) or substitutional disorder (2, b, 1). 

Distribution Laws And Regular Solid Solutions. For so-called regular solid solutions (15), Equation (9) still holds but by definition the expression for their enthalpy of mixing is ... 

Figure 4. Distribution of the ionic compounds AX and BX over the solid phase and the aqueous phase for different values of the distribution parameter D under the assumption that AX and BX form homogeneous regular solid solutions with a negative value for the interaction parameter W.

Substitutional Disorder In Regular Solid Solutions. Most simple ionic solutions in which substitution occurs in one sublattice only are not ideal, but regular 2, J3) Most complex ionic solid solutions in which substitution occurs in more than one sublattice are not only regular in the sense of Hildebrand s definition (15) but also exhibit substitutional disorder. The Equations describing the activities of the components as a function of the composition of their solid solutions are rather complex ( 7, V7, 1 ), and these can be evaluated best for each individual case. Both type II and type III distributions can result from these conditions. 

This solid solution still makes up the bulk of the solid particles after equilibration in an aqueous solution (59), since solid state diffusion is negligible at room temperature in these apatites (60), which have a melting point around 1500°C. These considerations and controversial results justify a thermodynamic analysis of the solubility data obtained by Moreno et al (58 ). We shall consider below whether the data of Moreno et al (58) is consistent with the required thermodynamic relationships for 1) an ideal solid solution, 2) a regular solid solution, 3) a subregular solid solution and 4) a mixed regular, subregular model for solid solutions. 

Figure 9. Ultimate activities of OHA and FA at the spinodal compositions in the model of regular solid solutions.

Cadmium in groundwater tends to be rapidly sorbed by any calcite present. The resultant solid then behaves like a (Ca,Cd)C03 symmetrical regular solid solution with an interaction parameter of Go = -0.8. Assume the calcite in a freshwater aquifer contains 1.0 mole percent CdC03 and that mCa = 3 x 10 M in the groundwater. Given also the solubility products rca(calcite) = 10" and ATcd(otavite, CdCO,) = 10 "- ... 

Given a value of iu or a for a binary, symmetrical, regular. solid solution and the solubility products for the pure end-member components, be able to compute the dissolved concentrations of either component at equilibrium with the solid solution, assuming the concentration of the other dissolved component is known. 

J. Sci.. in press). Indeed, in the case of a solid-solution with a small difference in the size of the substituting ions (relative to the size of the non-substituting ion), the first parameter, ao, is usually sufficient (8). Equations 5 and 6 then become identical to those of the "regular" solid-solution model of Hildebrand (9). For the case where both ao and ai parameters are needed, equations 5 and 6 become equivalent to those of the "subregular" solid-solution model of Thompson and Waldbaum (10). a model much used in high-temperature work. Equations 5 and 6 can also be shown equivalent to Margules activity coefficient series (11). 

Kgg values are evaluated from Thorstenson and Plummer s (3) equation 22, modified assuming a regular solid-solution model ... 

Critical mixing points can also be used to calculate the non-ideality of a solid-solution series. The critical temperature T of a SSAS system refers to the lowest possible temperature at which a complete solid-solution series may form (in. In a regular solid-solution series, a miscibility gap will occur only if an is greater than 2 and the following relation may be derived between ao, T and T the current temperature of the solid-solution system (2) ... 

When nickel (II, III) hydroxides form regular solid solutions in the whole range of compositions between p-Ni(OH)2 and P-NiOOH the experimental data can be... 

The so-called a-Ni(OH)2 y-NiOOH system forms regular solid solutions of Ni(II) and Ni(IV) components in the whole range of compositions between a-Ni(OH)2 and Ni02 A H20(s), without any participation of Ni(Ill) oxide hydroxides. Thus, Reaction (V.51) has to be modified. 

Assuming a regular solid solution model (Prieto 2009 Ruiz-Hernandez et al. 2010), the enthalpy of mixing at low zirconium content was fitted with a polynomial of the form ... 

Fig. 5. The ideal and regular solid solution models that predict surface segregations of the constituents with lower surface free energy...

If we assimilate the mineral to a regular solid solution and take for the excess energy that given by Grover (1977), the activity coefficients read as ... 

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