Solubility of Aluminum Fluoride, Fluorite, and Fluorophlogopite Minerals in Soils

The solubilities of AlF 3 (c), CaF 2 (fluorite), and KMg 3 AlSi 3 O 10 F 2 (fluorophlogopite) were investigated. Equilibrium was approached from both undersaturated and supersaturated conditions. The average equilibrium constant ( K °) determined was 10 −17.37 for AlF 3 (c), 10 −10.3 for CaF 2 , and 10 7.94 for KMg 3 AlSi 3 O 10 F 2 . Nine soil samples each of strongly acid, slightly acid, and alkaline soils were used for AlF 3 (c), CaF 2 , and KMg 3 AlSi 3 O 10 F 2 studies, respectively. The 1:5 soil/water suspensions, with and without added mineral, were shaken for 150 d. The F ‐ solubility for strongly acid and near neutral soils without added minerals was undersaturated with respect to AlF 3 (c) and CaF 2 , respectively. The F ‐ solubility for alkaline soils was close to that of KMg 3 AlSi 3 O 10 F 2 .