Double salts are salts containing more than one cation or anion, and are obtained by combination of two different salts which were crystallized in the same regular ionic lattice. salts are salts containing more than one cation or anion, and are obtained by combination of two different salts which were crystallized in the same regular ionic lattice. Examples of double salts include alums (with the general formula M^IM^III[SO₄]₂•12H₂O) or Tutton salts (with the general formula [M^I]₂M^II[SO₄]₂•6H₂O). Other examples are potassium sodium tartrate and bromlite.