Proverbs 25:20 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. (KJV JPS DBY WBS YLT)
Jeremiah 2:22 For though thou wash thee with nitre, and take thee much soap, yet thine iniquity is marked before me, saith the Lord GOD. (KJV JPS DBY YLT)