Natron is a salt (sodium carbonate and sodium bicarbonate) that was used in the mummification process to dry out the body of the deceased in order to assist in its preservation.
Citing this page:
Generalic, Eni. "Natron." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.