Niter

[Fr. & Pr. nitre, Sp., It., & Pg. nitro, Lat. nitrum, Gr. νίτρον. Cf. NATRON.]

1. (Chem.) A white, crystalline, semi-transparent salt, nitrate of potassa, having a pungent, saline taste. It occurs in nature as a crust of minute, silky crystals, and often as the result of the decomposition of animal matter in the presence of bases. It is largely used as an antiseptic, also in the manufacture of gunpowder, and in medicine as a diuretic and refrigerant;—called also saltpeter.
2. The native carbonate of soda; natron. [Obs. and very rare.]

As he that taketh away a garment in cold weather, and as vinegar upon niter, so is he that singeth songs to a heavy heart. Prov. xxv. 20. For though thou wash thee with niter, and take thee much soap, yet thine iniquity is marked before me. Jer. ii. 22. Cubic niter, a deliquescent salt, nitrate of soda, found as a native incrustation, like niter, in Peru and Chili, whence it is known as Chili saltpeter.