NITER (Hebrew, "nether"):
The niter of the ancients was a mineral alkaline salt, carbonate of soda, found in great quantities in Egypt. Natron Lake and Natron Valley derive their name from its presence in them; and they are still exploited for niter as they were in ancient times. In Egypt much niter was used of old for the embalming of bodies, and it was also known to the ancients that in smelting ore, niter quickened the process of flux. In the Old Testament niter is mentioned as a cleansing agent (Jer. ii. 22). It was also frequently employed for medicinal purposes. In Prov. xxv. 20 the effect of songs on a heavy heart is compared to the action of "vinegar upon niter." This is usually explained by the fact that niter effervesces when acids are mixed with it. Perhaps, however, the text should be emended; for the Septuagint reads: "as vinegar on a wound."