Double salt

Double salts are salts containing more than one cation or anion,hence the double in salt. They form when more than one salt is dissolved in a liquid and when together they crystallize in a regular pattern. A well-known double salt is alum containing two cations (potassium and aluminium) and a sulfate anion. Other examples are potassium sodium tartrate and bromlite.

Alums are double sulphates of a monovalent cation and a trivalent cation containing 24 water of crystallization.

Difference between a double salt and a complex... Double salts when dissolved in water dissociate into simple ions completely while complexes do not dissociate into simple ions and maintain the property of complexes.

"A double salt is a substance obtained by the combination of two different salts which crystallise together as a single substance but ionize as two distinct salts when dissolved in water."

When a double salt is formed by the chemical combination of two single salts (like, potassium tartrate and sodium tartrate), the properties of the double salt formed will not be the same as the properties of its component single salts.