A chemical, (soda, R. V., margin)
As he that taketh away a garment in cold weather, and as vinegar upon nitre, so is he that singeth songs to an heavy heart. (Proverbs 25:20)
(Lye, R. V.)
For though thou wash thee with nitre, and take thee much soap, yet thine iniquity is marked before me, saith the Lord God. (Jeremiah 2:22)