>Because potassium reacts with water vapor in the air, it is usually stored under anhydrous mineral oil or kerosene.
I once worked in a chemistry lab in college. There was a gallon jar with oil and a stick of potassium in it. Prof told us to get rid of it by throwing it in the river. We went to a pedestrian bridge over the river late at night, unscrewed the lid, and threw the jar in the river. The was a pause, then an explosion which shot flaming purple arcs about 30 feet in all directions On the surface of the river, and when the arcs hit they made smaller explosions with purple arcs. We decided it was time to make a hasty exit.