Nitre as used in the King James Version does not correspond to the present use of that term. Nitre or niter is now applied to sodium or potassium nitrate. The writer has in his collection a specimen of sodium carbonate, called in Arabic naTrun, which was taken from the extensive deposits in Lower Egypt where it is found as a deposit underneath a layer of common salt. Similar deposits are found in Syria and Asia Minor. This is probably the "nitre" of the Bible. the American Standard Revised Version has rendered niter "lye" in Jer 2:22, and "soda" in Pr 25:20. Soda or lye has been used as a cleansing agent from earliest times. It effervesces energetically, when treated with an acid; hence, the comparison in Pr 25:20 of the heavy-hearted man roiled by the sound of singing to the sizzling of soda on which vinegar has been poured.