potassium alum造句

"The most important alums are those of potassium sulfate (potassium alum, or potash alum, K2SO4*Al2(SO4)3*24H2O), ammonium sulfate, and sodium sulfate."

Since all forms of potassium alum are soluble in water, when the stone is wet or applied to wet skin, an invisible, fine layer of the mineral is rubbed off the stone and applied to the skins surface.