Factors that Affect the Solubility of Electrolytes

With many electrolytes, the lattice energy is somewhat greater than the hydration energy so that the dissolution of electrolytes in water is generally an endothermic process. Hence, the solubility of most electrolytes increases with increasing temperature. See Equation 2-13. A very few substances such as CaS04, have negative heats of solution and therefore exhibit a decrease in solubility with increase in temperature. 

The solubilities of solid electrolytes in organic solvents are generally lower than they are in water. Thus the solubility of PbS04 or SrS04 can be decreased by the addition of ethanol to water, which thereby facilitates their quantitative precipitation. The solubility decreased effected by the organic solvent probably reflects the influence of the lower dielectric constant which increased the energy required to dissociate the ions. Just 

Since solubility of electrolytes involves dissociation phenomena, factors affecting dissociation either directly (ionic strength) or indirectly (reactions involving ions formed) will inevitably affect solubility. These factors will now be considered in detail. 

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