In chemistry the term stannate refers to compounds of tin (Sn). Stannic acid (Sn(OH)4), the formal precursor to stannates, does not exist and is actually a hydrate of SnO2. The term is also used in naming conventions as a suffix; for example the hexachlorostannate ion is . In materials science, two kinds of tin oxyanions are distinguished: orthostannates contain discrete units (e.g. K4SnO4) or have a spinel structure (e.g. Mg2SnO4) metastannates with a stoichiometry MIISnO3, MSnO3 which may contain polymeric anions or may be sometimes better described as mixed oxides These materials are semiconductors. Examples Barium metastannate (BaSnO3) Cobalt stannate (Co2SnO4), primary constituent of the pigment cerulean blue Dysprosium stannate (Dy2Sn2O7) Potassium stannate (formally potassium hexahydroxostannate(IV), formula K2Sn(OH)6) Sodium stannate (formally sodium hexahydroxostannate(IV), formula Na2Sn(OH)6) See also Stannite References Oxometallates