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"Nitre" redirects here. For other meanings of the word "Niter" and "Nitre", see Nitre (disambiguation).
"Saltpeter" redirects here. For other meanings of the word "Saltpeter", see Saltpeter (disambiguation).
Not to be confused with natron.
KNO3 cryrtal.jpg
A niter crystal under a polarizing microscope
Category Nitrates
(repeating unit)
Strunz classification 05.NA.10
Dana classification
Crystal symmetry 2/m 2/m 2/m
Color white
Crystal habit druse or acicular
Crystal system orthorhombic
Cleavage very good on {001}; good on {010}
Fracture brittle
Mohs scale hardness 2
Luster vitreous
Streak white
Diaphaneity transparent
Specific gravity 2.10 (calc.)
Refractive index nα = 1.332
nβ = 1.504
nγ = 1.504
Solubility soluble
References [1][2][3]

Niter (American English) or nitre (most English-speaking countries) is the mineral form of potassium nitrate, KNO3, also known as saltpeter in America or saltpetre in other English speaking countries. Historically, the term "niter" was not well differentiated from natron, both of which have been very vaguely defined but generally refer to compounds of sodium or potassium joined with carbonate or nitrate ions.

Because of its ready solubility in water, niter is most often found in arid environments. A major source of sodium nitrate mineral ("Chile saltpeter", that is, nitratine) is the Atacama desert in Chile. Potassium and other nitrates are of great importance for use in fertilizers and, historically, gunpowder. Much of the world's demand is now met by synthetically produced nitrates, though the natural mineral is still mined and is still of significant commercial value.


Niter is a colorless to white mineral crystallizing in the orthorhombic crystal system. It usually is found as massive encrustations and efflorescent growths on cavern walls and ceilings where solutions containing alkali potassium and nitrate seep into the openings. It occasionally occurs as prismatic acicular crystal groups, and individual crystals commonly show twinning.


Niter as a term has been known since ancient times, although there is much historical confusion with natron (an impure sodium carbonate/bicarbonate), and not all of the ancient salts known by this name or similar names in the ancient world contained nitrate. The name is from the Greek νιτρων nitron from Ancient Egyptian netjeri, related to the Hebrew néter, for salt-derived ashes (their interrelationship is not clear).

The Hebrew néter may have been used as, or in conjunction with soap, as implied by Jeremiah 2:22, "For though thou wash thee with nitre, and take thee much sope…" However, it is not certain which substance (or substances) the Biblical "neter" refers to, with some suggesting sodium carbonate. Indeed, the Neo Latin word for sodium, natrium, is derived from this same class of desert minerals called natron (French) from Spanish natrón through Greek νίτρον (nitron), derived from Ancient Egyptian netjeri, referring to the carbonate sodium salts occurring in the deserts of Egypt, not the nitrated sodium salts typically occurring in the deserts of Chile (classically known as "Chilean saltpeter" and variants of this term).

A term (ἀφρόνιτρον) which translates as "foam of niter" was a regular purchase in a fourth-century AD series of financial accounts, and since it was expressed as being "for the baths" was probably used as soap.[4]

Niter was used to refer specifically to nitrated salts known as various types of saltpeter (only nitrated salts were good for making gunpowder) by the time niter and its derivative nitric acid were first used to name the element nitrogen, in 1790.

See also[edit]


  1. ^ Niter,, retrieved 2009-12-04 .
  2. ^ Niter,, retrieved 2009-12-04 .
  3. ^ Adiwidjaja, G.; Pohl, D. (2003), "Superstructure of α-phase potassium nitrate", Acta Crystallogr. C 59 (12): 1139–40, doi:10.1107/S0108270103025277 .
  4. ^ More conventional soap also appears in the accounts but was more expensive: John Matthews, The Journey of Theophanes, Yale UP 2006

External links[edit]