Caesium tungstate or cesium tungstate is an inorganic chemical compound with the formula . It is notable for forming a very dense liquid in solution (a solution containing 85.6g per 100g water has a specific gravity of 3.0133). The solution is used in diamond processing, since diamond sinks in it, whereas most other rocks float.
Caesium tungstate forms colorless crystals, which are strongly hygroscopic. A phase transition from orthorhombic to hexagonal crystal system occurs at 536 ðC.
Caesium tungstate can be obtained by the reaction between caesium chloride (CsCl) and silver tungstate (Ag<sub>2</sub>WO<sub>4</sub>) or the reaction between tungstic acid and caesium hydroxide.