American Tract Society Bible Dictionary
Not the substance used in making gunpowder, but natron, a mineral alkali composed of several salts of soda. It effervesces with vinegar, Proverbs 25:28 , and is still used in washing, Jeremiah 2:22 . Combined with oil, it makes a hard soap. It is found deposited in, or floating upon, certain lakes west of the Delta of Egypt.
These files are public domain and are a derivative of the topics are from American Tract Society Bible Dictionary published in 1859.
Rand, W. W. Entry for 'Nitre'. American Tract Society Bible Dictionary. https://www.studylight.org/dictionaries/eng/ats/n/nitre.html. 1859.