Calcium fluoride

Calcium fluoride is an inorganic salt of calcium, with the chemical formula CaF₂. It occurs in nature as the mineral known as fluorite or fluorspar.

Properties

Chemical

Calcium fluoride will react with a strong acid, such sulfuric acid to yield calcium sulfate and hydrogen fluoride.

CaF₂ + H₂SO₄ → 2 HF + CaSO₄

Physical

Calcium fluoride is a white solid compound. Single crystals are transparent. It is extremely poorly soluble in water (0.0016 g/100 mL at 20 °C) and insoluble in organic solvents. It has a melting point of 1,418 °C and boils at 2,533 °C.

Availability

Calcium fluoride occurs naturally as the mineral fluorite, that can be purchased from mineral sellers. Certain homeopathy tablets also contain calcium fluoride. Purer calcium fluoride is available from chemical suppliers.

Calcium fluoride optic objects, such as lens, windows, filters, prisms are an interesting application of the substance. At least one website offers many such items.

Preparation

Calcium fluoride can be prepared by reacting a fluoride, such as sodium fluoride with a soluble calcium salt, such as calcium chloride. Calcium fluoride precipitates out of the solution, which is filtered and fried.

Projects

• Make hydrofluoric acid
• Store elemental fluorine
• Thermite fluxing agent

Handling

Safety

Calcium fluoride has poor solubility in water. Contact with strong acids, such as sulfuric acid should be avoided, as it will generate toxic hydrofluoric acid. This includes gastric (hydrochloric) acid: do not swallow calcium fluoride.

Storage

Calcium fluoride should be stored away from strong acids.

Disposal

Calcium fluoride does not require any special disposal and can be dumped in the trash.

References

Relevant Sciencemadness threads

• Fluorine salts aqcuisition?