Natron is a white, crystalline hygroscopic mineral salt, primarily a mixture of sodium bicarbonate (common baking soda) and sodium carbonate (soda ash) with small amounts of sodium chloride (table salt) and sodium sulfate. Natron is somewhat antiseptic and is also an exfoliant and a desiccant. In ancient Egypt Natron was mined as a powdery solid from dry lake beds near the Nile and put to a wide variety of uses, including mummification (drying out a corpse to prevent tissue decay). Because it has strong grease-cutting properties, Natron has also been associated with soap production. The chemical symbol for sodium, Na, derives from this word through the later Roman term natrium. It has also been referred to as Impure salt.