Natron is a salty chemical found near Cairo, Wadi-Natron, and south of Thebes. It is actually a coumpound of sodium carbonate and sodium bicarbonate (to the likes of people like myself that translates to salt and baking soda).

What makes it special however, is that it was used as a disinfectant and desiccating agent in the mummification process. The ancient egyptians used to collect natron from dried up river beds, put it into linen bags and place them inside the corpse for around 40 days in order to draw out the moisture from the tissues.