Identifying Potassium Minerals

Flame Test. Volatile potassium salts give a characteristic pale violet flame color. The potassium flame will, however, commonly be obscured bye the stronger yellow flame of sodium. This difficulty can be overcome bye filtering the flame through a piece of blue glass. The sodium flame, being a mono – chromatic light, cannot pass through the blue glass, while the violet flame of potassium will be visible.

When the potassium does not exist in the mineral in a volatile state, as in the case with potassium silicates, the powdered mineral must be first thoroughly mixed with gypsum (CaSO₄. 2H₂O) and the mixture introduce into the Bunsen burner flame on a platinum wire. There will be a reaction between the two, and the potassium will be liberated in the form of a sulphate, which, being a volatile salt, will give the flame color. It will be momentary in duration and must be viewed through the blue glass.