3. Physico-chemical properties

Calcium phosphates and apatites have highly variable properties, depending very much on their composition. What they have in common is that they are all white solids (unless doped with colored ions), most of them not very soluble and some very insoluble. They are thermally stable, but easily change formula through substitution of constituent elements.

• Thermal decomposition

  Apatites are very thermally stable. Fluoroapatite melts at 1,644°C, but decomposition can occur at lower temperatures under certain atmospheres. For example, fluoroapatite can be converted to hydroxyapatite by heating in a steam stream at 1,360°C for 48 hours. Heating fluoroapatite in a vacuum above 1,600°C results in the loss of CaF ₂ or POF ₃ . Chloroapatite...