Ionic solid solution general formula

An ionic solid solution, on the other hand, is of variable composition. Its chemical formula can not be written in simple integer ratio numbers. A theoretical example is that of two compounds AX and BX which form a solid solution of the general formula ... 

The Kelvin equation may also be applied to the equilibrium solubility of a solid in a liquid. In this case the ratio p/p0 in Equation (40) is replaced by the ratio a/a0, where a0 is the activity of dissolved solute in equilibrium with a flat surface, and a is the analogous quantity for a spherical surface. For an ionic compound having the general formula MmXn, the activity of a dilute solution is related to the molar solubility S as follows ... 

HUP and many other natural or synthetic compounds belong to the torbernite mineral group of general formula M, y(U02X04)(H30)y. 3H2O where X is P or As and M" " is a cation such as K, NH4", Na, Li, Ca, Pb, Ag or AP. The role of interlayer cations and water molecules in torbernite is similar to that in zeolites, clay minerals, some feldspars and micas, jarosites, autunites and clathrate compounds. In all these materials solid solutions between protonic and ionic derivatives are readily observed ion exchange and protonic conductivity can thus be expected. 

Calcium phosphate ceramics are ceramics with varying calcium-to-phosphate ratios. Among them, the apatite ceramics, defined by the chemical formula M,o(X04)6Z2, have been studied most. The apatites form a range of solid solutions as a result of ionic substitution at the XO , or Z sites. In general, apatites are nonstoichiometric and contain less than 10 mol of ions, less than 2 mol of Z" ions, and exactly 6 mol of XOJ" ions (Van Raemdonck et al., 1984). The species is typically a bivalent metallic cation, such as Ca, Sr +, Ba ", Pb ", or Cd2+. The XO species is typically one of the following trivalent anions AsO , VO, CrO , or MnO. The monovalent 7r ions are usually F", OH , Br , or Cj (Van Raemdonck et al., 1984). 

Lastly, we turn our attention to the gray area between metallic and ionic solids. An interstitial is a compound that is formed when another atom (typically having about the same electronegativity as the metal) is small enough to occupy some of the interstitial sites in a metallic solid. The elements H, B, C, and N are common examples. For instance, H atoms can occupy the interstitial sites in Pd metal to form compounds having the general formula PdH . Interstitials can also be considered as solid solutions, where the smaller atom serves as the solute and the larger... 

Reactions (3) and (4) proceed in solid electrolytes, for instance, in solid solutions based on lanthanum gallate of the general formula Lai.xAxGai.yBy03.(x+yy2(A = Ca, Sr, Ba B = Mg, Zn). These systems have high ionic conductivity caused by high concentration of oxygen vacancies [14, 15] and they are wide gap semiconductors, hence, concentrations of intrinsic electronic defects in these compounds are very low. 

In several of the studies of aqueous chemistry of aluminum that have been made since about 1950, polynuclear complexing mechanisms have been proposed to identify and describe the dissolved aluminum hydroxide complex species (3, JO, 11). The formulae proposed have generally been based on stoichiometric considerations and pH measurements assuming the polynuclear species were ionic, and that equilibrium was attained. The complex ions reported by Hsu and Bates (8) were single six-mem-bered rings Ale (OH) 12 or multiples of this unit. Johansson (JO) identified a structural unit containing 13 aluminum and 40 oxygen atoms with various numbers of protons in crystalline basic aluminum sulfate. Because this solid formed readily, the same structural unit of aluminum was proposed as a solute species. Most of the proposed formulae for polynuclear complexes, however, have not been derived from structural considerations. 

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