Solubility of Calcium Fluoride

Illustration showing the solubility of CaF₂ as a function of pH, represented by the solid blue curve. The predominate form of fluoride in solution is shown by the ladder diagram along the x-axis, with the black rectangle showing the region where both HF and F^– are important species. Note that the solubility of CaF₂ is independent of pH for pH levels greater than 4.17, and that its solubility increases dramatically at lower pH levels where HF is the predominate species. Because the solubility of CaF₂ spans several orders of magnitude, its solubility is shown in logarithmic form.