Cobalt-ammonium sulfate is an inorganic compound with the chemical formula  (NH₄)₂Co(SO₄)₂. It is usually found in the form of hexahydrate, i.e., (NH₄)₂Co(SO₄)₂·6H₂O. It is a blue crystal, sometimes referred to as Moore blue or Saruman blue, because its color is similar to the historical blue pigment Cobalt Blue.

Cobalt-ammonium sulfate can be obtained by reacting soluble cobalt salts with ammonium sulfate solutions. This compound has a vivid blue color in solution, so it is used not only as a chemical reagent but also as an indicator and pigment.

1. Pigment: Cobalt-ammonium sulfate is a blue inorganic pigment used in glass, ceramics and paintings, known for its vivid color and stability.

2. Indicator: In chemical analysis, ammonium cobalt sulfate can be used as an indicator for the detection of sulfate ions and anions in coordination titration.

3. Electroplating: Ammonium cobalt sulfate can be used as part of the electroplating solution to coat a layer of cobalt on the surface of the metal.

4. Catalyst: In some chemical reactions, ammonium cobalt sulfate can be used as a catalyst to promote the reaction.

5. Battery materials: Cobalt-ammonium sulfate can be used in some types of batteries as a component of electrode materials.

6. Biology and Medicine: Cobalt-ammonium sulfate has been used to stain cells in biological research and as a reagent for certain medical tests.

7. Photosensitive materials: Cobalt ammonium sulfate has been used in the preparation of photosensitive materials in the photography and printing industries.

8. Ceramic Materials: Cobalt-ammonium sulfate is used in the production of special types of ceramics, such as electronic ceramics and catalyst carriers.