Solubilities in aqueous nitrate solutions that appear to reverse the law of mass action

and many alkali nitrate salts increases when another nitrate-bearing electrolyte is added to solution. These occurrences were in concentrated solutions with insufficient water to provide all ions their preferred hydration number without sharing waters between ions. This water deficit results in the formation of contact ion-pairs as well as larger ion-clusters. These ion-clusters may be favored when there is more than one type of monovalent cation present.