Before revision: Only a small amount of elemental iodine will dissolve in water, and adding potassium iodide allows a much larger amount of elemental iodine to dissolve through the reaction of I2-I3 .
After revision: Only a small amount of elemental iodine will dissolve in water, but triiodides are highly soluble; potassium iodide thus serves as a phase transfer catalyst in the tincture .