Nitre
Summary
Nitre in Scripture refers to natron, a naturally occurring sodium carbonate used for cleansing, not the modern potassium nitrate.
☩Biblical References
Nitre (Hebrew nether) is mentioned twice in the Old Testament. Proverbs compares singing songs to a heavy heart to vinegar upon nitre—an apt comparison since the acid of vinegar causes sodium carbonate to effervesce violently. Jeremiah mentions washing with nitre and much soap, indicating its use as a cleaning agent.
☩Nature of the Substance
Biblical nitre is not the saltpeter (potassium nitrate) known by that name today, but rather natron or native sodium carbonate. This substance was found abundantly in Egypt, especially in the Wady Natrun (Valley of Natron), and was used for washing and cleansing. The Egyptians also used it in mummification.