These materials are double salts, which means that they contain two different cations, M+ and M'2+ crystallized in the same regular ionic lattice.
The divalent cation can be magnesium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc or cadmium.
[3] The robustness is the result of the complementary hydrogen-bonding between the tetrahedral anions and cations as well their interactions with the metal aquo complex [M(H2O)6]2+.
They are named for Alfred Edwin Howard Tutton, who identified and characterised a large range of these salts around 1900.
[7] Such salts were of historical importance because they were obtainable in high purity and served as reliable reagents and spectroscopic standards.