Editing Potassium nitrate

{{short description|Chemical compound}}
{{redirect|Saltpeter|other uses|Saltpeter (disambiguation)}}
{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 476994711
| Reference = <ref>{{GESTIS|Name=Potassium nitrate|ZVG=3630|CAS=7757-79-1|Date=2007-03-09}}</ref>
| Name = Potassium nitrate
| ImageFile = Potassium nitrate.jpg
| ImageName = Potassium nitrate
| ImageFileL1 = potassium nitrate structure.svg
| ImageFileR1 = Potassium-nitrate-superstructure-unit-cell-3D-sf.png
| IUPACName = Potassium nitrate
| OtherNames = {{Unbulleted list|Saltpeter|Saltpetre|Nitrate of potash|Nitre}}
| Section1 = {{Chembox Identifiers
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = RU45X2JN0Z
| KEGG_Ref = {{keggcite|correct|kegg}}
| KEGG = D02051
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 1644029
| InChI = 1/K.NO3/c;2-1(3)4/q+1;-1
| InChIKey = FGIUAXJPYTZDNR-UHFFFAOYAM
| SMILES = [K+].[O-][N+]([O-])=O
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/K.NO3/c;2-1(3)4/q+1;-1
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = FGIUAXJPYTZDNR-UHFFFAOYSA-N
| CASNo = 7757-79-1
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 24434
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 22843
| UNNumber = 1486
| RTECS = TT3700000
| EINECS = 231-818-8
}}
| Section2 = {{Chembox Properties
| Formula = KNO<sub>3</sub>
| MolarMass = 101.1032 g/mol
| Appearance = white solid
| Odor = odorless
| Solubility = {{ubl|133 g/L (0&nbsp;°C)|316 g/L (20&nbsp;°C)|383 g/L (25&nbsp;°C)|2439 g/L (100&nbsp;°C)}}<ref name=b1>{{cite book |pages=5–6 |chapter=2 |chapter-url=https://books.google.com/books?id=Q1yJNr92-YcC&pg=PA5 |title=Pyrotechnic Chemistry |author1=B. J. Kosanke |author2=B. Sturman |author3=K. Kosanke |author4=I. von Maltitz |author5=T. Shimizu |author6=M. A. Wilson |author7=N. Kubota |author8=C. Jennings-White |author9=D. Chapman |display-authors=3|publisher=Journal of Pyrotechnics |year=2004 |isbn=978-1-889526-15-7 |url-status=live |archive-url=https://web.archive.org/web/20160505033849/https://books.google.com/books?id=Q1yJNr92-YcC&pg=PA5 |archive-date=2016-05-05}}</ref>
| SolubleOther = slightly soluble in [[ethanol]]<br /> soluble in [[glycerol]], [[ammonia]]
| Density = 2.109 g/cm<sup>3</sup> (16&nbsp;°C)
| MeltingPtC = 334
| BoilingPtC = 400
| BoilingPt_notes = (decomposes)
| pKb = 15.3<ref>Kolthoff, Treatise on Analytical Chemistry, New York, Interscience Encyclopedia, Inc., 1959.</ref>
| RefractIndex = 1.335, 1.5056, 1.5604
| MagSus = −33.7·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
| Section3 = {{Chembox Structure
| Coordination =
| CrystalStruct = [[Orthorhombic]], [[Aragonite]]
}}
| Section4 = {{Chembox Thermochemistry
| DeltaHf = −494.00 kJ/mol
| HeatCapacity = 95.06 J/mol K
}}
| Section7 = {{Chembox Hazards
| ExternalSDS = [http://www.inchem.org/documents/icsc/icsc/eics0184.htm ICSC 0184]
| GHSPictograms = {{GHS03}} {{GHS exclamation mark}}
| HPhrases = {{H-phrases|272|315|319|335}}
| PPhrases = {{P-phrases|102|210|220|221|280}}
| MainHazards = Oxidant, harmful if swallowed, inhaled, or absorbed on skin. Causes irritation to skin and eye area.
| NFPA-H = 1
| NFPA-F = 0
| NFPA-R = 0
| NFPA-S = OX
| FlashPt = non-flammable (oxidizer)
| LD50 = 1901 mg/kg (oral, rabbit)<br />3750 mg/kg (oral, rat)<ref>{{cite journal | last1=Ema | first1=M. | last2=Kanoh | first2=S. | title=[Studies on the pharmacological bases of fetal toxicity of drugs. III. Fetal toxicity of potassium nitrate in 2 generations of rats] | journal=Nihon Yakurigaku Zasshi. Folia Pharmacologica Japonica | volume=81 | issue=6 | date=1983 | issn=0015-5691 | pmid=6618340 | pages=469–480| doi=10.1254/fpj.81.469}}</ref>
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Potassium nitrite]]
| OtherCations = {{ubl|[[Lithium nitrate]]|[[Sodium nitrate]]|[[Rubidium nitrate]]|[[Caesium nitrate]]|[[Ammonium nitrate]]|[[Silver nitrate]]|[[Calcium nitrate]]}}
| OtherCompounds = {{ubl|[[Potassium sulfate]]|[[Potassium chloride]]}}
}}
}}

'''Potassium nitrate''' is a [[chemical compound]] with a sharp, salty, bitter taste and the [[chemical formula]] {{chem2|KNO3|auto=1}}. It is a [[potassium]] [[Salt (chemistry)|salt]] of [[nitric acid]]. This salt consists of potassium [[cations]] {{chem2|K+}} and [[nitrate]] [[anions]] {{chem2|NO3−}}, and is therefore an [[alkali metal nitrate]]. It occurs in nature as a mineral, [[niter]] (or ''nitre'' outside the United States).<ref name=SOED>{{cite book |title = Shorter [[Oxford English Dictionary]] |year = 2007 |edition = 6th |pages = 3804 |publisher = [[Oxford University Press]] |location = United Kingdom |isbn = 9780199206872}}</ref> It is a source of [[nitrogen]], and nitrogen was named after niter. Potassium nitrate is one of several nitrogen-containing compounds collectively referred to as '''saltpetre''' (or '''saltpeter''' in the United States).<ref name=SOED/>

Major uses of potassium nitrate are in [[fertilizer]]s, [[Tree stump#Stump removal|tree stump removal]], [[rocket propellant]]s and [[firework]]s. It is one of the major constituents of traditional [[gunpowder]] (black powder).<ref name="auto1">{{Cite journal |last=Lauer |first=Klaus |date=1991 |title=The history of nitrite in human nutrition: A contribution from German cookery books |journal=Journal of Clinical Epidemiology |volume=44 |issue=3 |pages=261–264 |doi=10.1016/0895-4356(91)90037-a |issn=0895-4356 |pmid=1999685}}</ref> In [[processed meat]]s, potassium nitrate reacts with [[hemoglobin]] and [[myoglobin]] generating a red color.<ref>{{Cite journal |last=Haldane |first=J. |date=1901 |title=The Red Colour of Salted Meat |journal=The Journal of Hygiene |volume=1 |issue=1 |pages=115–122 |issn=0022-1724 |pmc=2235964 |pmid=20474105 |doi=10.1017/S0022172400000097}}</ref>

==Etymology==
Nitre, or potassium nitrate, because of its early and global use and production, has many names.

As for nitrate, Egyptian and Hebrew words for it had the consonants n-t-r, indicating likely [[cognate|cognation]] in the Greek ''nitron'', which was Latinised to ''nitrum'' or ''nitrium''. Thence Old French had ''niter'' and Middle English ''nitre''. By the 15th century, Europeans referred to it as ''saltpetre'',<ref>{{cite book|last1=Spencer|first1=Dan|title=Saltpeter:The Mother of Gunpowder|date=2013|publisher=Oxford University Press|location=Oxford, UK|isbn=9780199695751|pages=256}}</ref> specifically Indian saltpetre (Chilean saltpetre is sodium nitrate<ref name="brit1">{{cite news |url=https://www.britannica.com/science/saltpeter |title=Saltpetre &#124; Definition, Uses, & Facts &#124; Britannica |date=3 May 2024}}</ref>) and later as ''nitrate of potash,'' as the chemistry of the compound was more fully understood.

The Arabs called it "Chinese snow" ({{langx|ar|ثلج الصين|thalj al-ṣīn}}) as well as ''bārūd'' ({{lang|ar|بارود}}), a term of uncertain origin that later came to mean [[gunpowder]]. It was called "Chinese salt" by the Iranians/Persians<ref>{{cite book|author=Peter Watson|title=Ideas: A History of Thought and Invention, from Fire to Freud|url=https://books.google.com/books?id=CVNoJydnGAoC&pg=PA304|year=2006|publisher=HarperCollins|isbn=978-0-06-093564-1|page=304|url-status=live|archive-url=https://web.archive.org/web/20151017152857/https://books.google.com/books?id=CVNoJydnGAoC&pg=PA304|archive-date=2015-10-17}}</ref><ref>{{cite book |url=https://books.google.com/books?id=1h9zzSH-NmwC&pg=PA365 |title=The age of wars of religion, 1000–1650: an encyclopedia of global warfare and civilization |author=Cathal J. Nolan |access-date=2011-11-28 |volume=1 of Greenwood encyclopedias of modern world wars |year=2006 |publisher=Greenwood Publishing Group |isbn=978-0-313-33733-8 |page=365 |quote=In either case, there is linguistic evidence of Chinese origins of the technology: in Damascus, Arabs called the saltpeter used in making gunpowder "Chinese snow," while in Iran it was called "Chinese salt." |url-status=live |archive-url=https://web.archive.org/web/20140101045832/http://books.google.com/books?id=1h9zzSH-NmwC&pg=PA365 |archive-date=2014-01-01}}</ref><ref>{{cite book |url=https://books.google.com/books?id=aG0gAAAAMAAJ |title=English artillery, 1326–1716: being the history of artillery in this country prior to the formation of the Royal Regiment of Artillery |author=Oliver Frederick Gillilan Hogg |year=1963|publisher=Royal Artillery Institution |page=42 |quote=The Chinese were certainly acquainted with saltpetre, the essential ingredient of gunpowder. They called it Chinese Snow and employed it early in the Christian era in the manufacture of fireworks and rockets.}}</ref> or "salt from Chinese salt marshes" ({{langx|fa|نمک شوره چينی}} ''{{Transliteration|fa|DIN|namak shūra chīnī}}'').<ref name="Partington" />{{rp|335}}<ref>{{cite book |url=https://books.google.com/books?id=xrNDwP0pS8sC&q=namak+shura&pg=PA194 |title=Science and Civilisation in China: Volume 5, Chemistry and Chemical Technology, Part 4, Spagyrical Discovery and Invention: Apparatus, Theories and Gifts |volume=5|issue=Issue 4 of Science and Civilisation in China|first1=Joseph |last1=Needham |first2= Ping-Yu |last2= Yu |editor-first=Joseph|editor-last=Needham|others=Contributors Joseph Needham, Lu Gwei-Djen, Nathan Sivin|access-date=2014-11-21 |edition=illustrated, reprint |year=1980 |publisher=Cambridge University Press |isbn=978-0521085731 |page=194}}</ref> The [[Tiangong Kaiwu]], published in the 17th century by members of the [[Qing dynasty]], detailed the production of gunpowder and other useful products from nature.

==Historical production==<!-- This section is linked from [[Gunpowder]] and from [[Urine]]-->
{{See also|Nitre#Availability}}

===From mineral sources===
In [[Maurya Empire|Mauryan India]] saltpeter manufacturers formed the Nuniya & Labana
[[caste]].<ref>{{cite book |last = Sen |first = Sudipta |date = 2019 |isbn = 978-0-300-11916-9 |page = 318 | title = Ganges: The Many Pasts of an Indian River |location = New Haven |url = https://books.google.com/books?id=FOV8DwAAQBAJ&pg=PT695 |publisher = Yale University Press}}</ref> Saltpeter finds mention in [[Kautilya|Kautilya's]] [[Arthashastra]] (compiled 300BC – 300AD), which mentions using its poisonous smoke as a weapon of war,<ref>{{cite book |last = Roy |first = Kaushik |date = 2014 |title = Military Transition in Early Modern Asia, 1400–1750 |page = 19 |isbn = 978-1-7809-3765-6 |location = London |publisher = Bloomsbury Academic |url = https://books.google.com/books?id=KyVnAwAAQBAJ&pg=PA19}}</ref> although its use for propulsion did not appear until medieval times.

A purification process for potassium nitrate was outlined in 1270 by the chemist and engineer [[Hasan al-Rammah]] of [[Syria]] in his book ''al-Furusiyya wa al-Manasib al-Harbiyya'' (''The Book of [[furusiyya|Military Horsemanship]] and Ingenious War Devices''). In this book, al-Rammah describes first the purification of ''barud'' (crude saltpeter mineral) by boiling it with minimal water and using only the hot solution, then the use of [[potassium carbonate]] (in the form of [[wood ash]]es) to remove calcium and magnesium by precipitation of their carbonates from this solution, leaving a solution of purified potassium nitrate, which could then be dried.<ref>[[Ahmad Y Hassan]], [http://www.history-science-technology.com/Articles/articles%202.htm Potassium Nitrate in Arabic and Latin Sources] {{webarchive|url=https://web.archive.org/web/20080226105129/http://www.history-science-technology.com/Articles/articles%202.htm |date=2008-02-26}}, ''History of Science and Technology in Islam''.</ref> This was used for the manufacture of gunpowder and explosive devices. The terminology used by al-Rammah indicated the gunpowder he wrote about originated in China.<ref>{{cite book|author=Jack Kelly|title=Gunpowder: Alchemy, Bombards, and Pyrotechnics: The History of the Explosive that Changed the World|url=https://books.google.com/books?id=8xfs8tC8Ow0C&pg=PA22|year=2005|publisher=Basic Books|isbn=978-0-465-03722-3|page=22|url-status=live|archive-url=https://web.archive.org/web/20160511041453/https://books.google.com/books?id=8xfs8tC8Ow0C&pg=PA22|archive-date=2016-05-11}}</ref>

At least as far back as 1845, [[nitratite]] deposits were exploited in Chile and California.

===From caves===
Major natural sources of potassium nitrate were the deposits crystallizing from cave walls and the accumulations of [[bat guano]] in caves.<ref>{{cite book |title=Notes on Making Saltpetre from the Earth of the Caves |author=Major George Rains |year=1861 |page=14 |publisher=Daily Delta Job Office |location=New Orleans, LA |access-date=September 13, 2012 |url=https://archive.org/stream/notesonmakingsal01rain |url-status=live |archive-url=https://web.archive.org/web/20130729072115/https://archive.org/stream/notesonmakingsal01rain |archive-date=July 29, 2013}}</ref> Extraction is accomplished by immersing the guano in water for a day, filtering, and harvesting the crystals in the filtered water. Traditionally, guano was the source used in [[Laos]] for the manufacture of gunpowder for [[Rocket Festival|''Bang Fai'']] rockets.<ref name="joshi14">{{cite journal |doi=10.56431/p-je383z |title=Environmentally and Economically Feasibility Manufacturing Process of Potassium Nitrate for Small Scale Industries: A Review |date=2014 |last1=Joshi |first1=Chirag S. |last2=Shukla |first2=Manish R. |last3=Patel |first3=Krunal |last4=Joshi |first4=Jigar S. |last5=Sahu |first5=Omprakash |journal=International Letters of Chemistry, Physics and Astronomy |volume=41 |pages=88–99 |doi-access=free}}</ref>

[[Calcium nitrate]], or lime saltpetre, was discovered on the walls of stables, from the urine of barnyard animals.<ref name=brit1/>

=== Nitraries ===<!-- Redirect from [[Nitrary]] -->
{{See also|Saltpetre works}}
Potassium nitrate was produced in a ''nitrary'' or "[[saltpetre works]]".<ref>{{cite book|author1=John Spencer Bassett|author2=Edwin Mims|author3=William Henry Glasson |author4=William Preston Few |author5=William Kenneth Boyd |author6=William Hane Wannamaker|display-authors=3|title=The South Atlantic Quarterly|url=https://books.google.com/books?id=j7p9AAAAMAAJ&q=nitraries|access-date=22 February 2013|year=1904|publisher=Duke University Press}}</ref> The process involved burial of excrements (human or animal) in a field beside the nitraries, watering them and waiting until leaching allowed saltpeter to migrate to the surface by [[efflorescence]]. Operators then gathered the resulting powder and transported it to be concentrated by [[ebullition]] in the boiler plant.<ref>{{cite book |author=Paul-Antoine Cap |title=Etudes biographiques pour servir à l'histoire des sciences ...: sér. Chimistes |url=https://books.google.com/books?id=1OFHAAAAIAAJ&pg=PA294 |access-date=23 February 2013 |year=1857 |publisher=V. Masson |pages=294–}}</ref><ref>{{cite book |author=Oscar Gutman |title=Monumenta pulveris pyrii. Repr |url=http://www.e-rara.ch/zut/content/pageview/4082499 |year=1906 |publisher=Artists Press Balham |pages=50–}}</ref>

Besides "[[Montpellier|Montepellusanus]]", during the thirteenth century (and beyond) the only supply of saltpeter across Christian Europe (according to "De Alchimia" in 3 manuscripts of Michael Scot, 1180–1236) was "found in Spain in Aragon in a certain mountain near the sea".<ref name="Partington">{{cite book |author = James Riddick Partington |title = A history of Greek fire and gunpowder |year = 1999 |publisher = JHU Press |isbn = 978-0-8018-5954-0 |url = https://archive.org/details/historyofgreekfi00part}}</ref>{{rp|89, 311}}<ref>{{cite book |author = Alexander Adam |title = A compendious dictionary of the Latin tongue: for the use of public Seminar and private March 2012 |year = 1805 |publisher = Printed for T. Cachorro and W. Davies, by C. Stewart, London, Bell and Bradfute, W. Creech}}</ref>

In 1561, [[Elizabeth I]], Queen of England and Ireland, who was at war with [[Philip II of Spain]], became unable to import saltpeter (of which the [[Kingdom of England]] had no home production), and had to pay "300 pounds gold" to the German captain Gerrard Honrik for the manual "Instructions for making saltpeter to growe" (the secret of the "''Feuerwerkbuch''" -the nitraries-).<ref>SP Dom Elizabeth vol.xvi 29–30 (1589)</ref>

=== Nitre bed ===<!-- Redirect from [[Nitre bed]] -->
A ''nitre bed'' is a similar process used to produce nitrate from excrement. Unlike the leaching-based process of the nitrary, however, one mixes the excrements with soil and waits for soil microbes to convert amino-nitrogen into nitrates by [[nitrification]]. The nitrates are extracted from soil with water and then purified into saltpeter by adding wood ash. The process was discovered in the early 15th century and was very widely used until the Chilean mineral deposits were found.<ref>{{cite journal |last1=Narihiro |first1=Takashi |last2=Tamaki |first2=Hideyuki |last3=Akiba |first3=Aya |last4=Takasaki |first4=Kazuto |last5=Nakano |first5=Koichiro |last6=Kamagata |first6=Yoichi |last7=Hanada |first7=Satoshi |last8=Maji |first8=Taizo |display-authors=3|title=Microbial Community Structure of Relict Niter-Beds Previously Used for Saltpeter Production |journal=PLOS ONE |date=11 August 2014 |volume=9 |issue=8 |pages=e104752 |doi=10.1371/journal.pone.0104752|pmid=25111392 |pmc=4128746 |bibcode=2014PLoSO...9j4752N |doi-access=free}}</ref>

The Confederate side of the American Civil War had a significant shortage of saltpeter. As a result, the [[Nitre and Mining Bureau]] was set up to encourage local production, including by nitre beds and by providing excrement to government nitraries. On November 13, 1862, the government advertised in the Charleston Daily Courier for 20 or 30 "able bodied Negro men" to work in the new nitre beds at Ashley Ferry, S.C. The nitre beds were large rectangles of rotted manure and straw, moistened weekly with urine, "dung water", and liquid from privies, cesspools and drains, and turned over regularly. The National Archives published payroll records that account for more than 29,000 people compelled to such labor in the state of Virginia. The South was so desperate for saltpeter for gunpowder that one Alabama official reportedly placed a newspaper ad asking that the contents of chamber pots be saved for collection. In South Carolina, in April 1864, the Confederate government forced 31 enslaved people to work at the Ashley Ferry Nitre Works, outside Charleston.<ref>{{cite news |last1=Ruane |first1=Michael |title=During the Civil War, the enslaved were given an especially odious job. The pay went to their owners |url=https://www.washingtonpost.com/history/2020/07/09/national-archives-slavery-payroll-receipts-civil-war-confederacy/ |newspaper=Washington Post |access-date=10 July 2020}}</ref>

{{anchor|LeConte}}Perhaps the most exhaustive discussion of the niter-bed production is the 1862 [[Joseph LeConte|LeConte]] text.<ref name="LeConte">{{cite book|url=http://docsouth.unc.edu/imls/lecontesalt/leconte.html|title=Instructions for the Manufacture of Saltpeter|author=Joseph LeConte|publisher=South Carolina Military Department|location=Columbia, S.C.|page=14|year=1862|access-date=2007-10-19|url-status=live|archive-url=https://web.archive.org/web/20071013174033/http://docsouth.unc.edu/imls/lecontesalt/leconte.html|archive-date=2007-10-13}}</ref> He was writing with the express purpose of increasing production in the [[Confederate States]] to support their needs during the [[American Civil War]]. Since he was calling for the assistance of rural farming communities, the descriptions and instructions are both simple and explicit. He details the "French Method", along with several variations, as well as a "Swiss method". N.B. Many references have been made to a method using only straw and urine, but there is no such method in this work.

====French method====
[[Anne Robert Jacques Turgot|Turgot]] and [[Lavoisier]] created the ''Régie des Poudres et Salpêtres'' a few years before the [[French Revolution]]. Niter-beds were prepared by mixing [[manure]] with either [[mortar (masonry)|mortar]] or wood ashes, common earth and organic materials such as [[straw]] to give porosity to a compost pile typically {{convert|4|ft|m}} high, {{convert|6|ft|m}} wide, and {{convert|15|ft|m}} long.<ref name="LeConte"/> The heap was usually under a cover from the rain, kept moist with [[urine]], turned often to accelerate the decomposition, then finally [[Leaching (chemical science)|leached]] with water after approximately one year, to remove the soluble [[calcium nitrate]] which was then converted to potassium nitrate by filtering through [[potash]].

====Swiss method====
[[Joseph LeConte]] describes a process using only urine and not dung, referring to it as the ''Swiss method''. Urine is collected directly, in a sandpit under a stable. The sand itself is dug out and leached for nitrates which are then converted to potassium nitrate using potash, as above.<ref>{{Cite book |last=LeConte |first=Joseph |url=https://docsouth.unc.edu/imls/lecontesalt/menu.html |title=Instructions for the Manufacture of Saltpetre. |publisher=Charles P. Pelham, State Printer |year=1862}}</ref>

===From nitric acid===
From 1903 until the [[World War I]] era, potassium nitrate for black powder and fertilizer was produced on an industrial scale from [[nitric acid]] produced using the [[Birkeland–Eyde process]], which used an electric arc to oxidize nitrogen from the air. During World War I the newly industrialized [[Haber process]] (1913) was combined with the [[Ostwald process]] after 1915, allowing Germany to produce nitric acid for the war after being cut off from its supplies of mineral sodium nitrates from Chile (see [[nitratite]]).

==Modern production==
Potassium nitrate can be made by combining [[ammonium nitrate]] and [[potassium hydroxide]].

:{{chem2|NH4NO3 + KOH → NH3 + KNO3 + H2O}}

An alternative way of producing potassium nitrate without a by-product of ammonia is to combine ammonium nitrate, found in [[Ice pack#Instant ice packs|instant ice packs]],<ref>{{Cite news|url=https://home.howstuffworks.com/refrigerator7.htm|title=How Refrigerators Work|date=2006-11-29|work=HowStuffWorks|access-date=2018-11-02|language=en}}</ref> and [[potassium chloride]], easily obtained as a sodium-free [[salt substitute]].

:{{chem2|NH4NO3 + KCl → NH4Cl + KNO3}}

Potassium nitrate can also be produced by neutralizing [[nitric acid]] with potassium hydroxide. This reaction is highly exothermic.

:{{chem2|KOH + HNO3 → KNO3 + H2O}}

On industrial scale it is prepared by the double displacement reaction between [[sodium nitrate]] and potassium chloride.
:{{chem2|NaNO3 + KCl → NaCl + KNO3}}

==Properties==
Potassium nitrate has an [[orthorhombic]] crystal structure at room temperature,<ref name="Adiwidjaja&Pohl">{{cite journal | title = Superstructure of α-phase potassium nitrate | first1 = G. | last1 = Adiwidjaja | first2 = D. | last2 = Pohl | journal = [[Acta Crystallographica Section C]] | year = 2003 | volume = 59 | issue = 12 | pages = i139–i140 | doi = 10.1107/S0108270103025277 | pmid = 14671340 | bibcode = 2003AcCrC..59I.139A}}</ref> which transforms to a trigonal system at {{convert|128|C|F}}. On cooling from {{convert|200|C|F}}, another trigonal phase forms between {{convert|124|C|F}} and {{convert|100|C|F}}.<ref>{{cite journal | title = The crystal structures of γ- and β-KNO<sub>3</sub> and the α ← γ ← β phase transformations | first1 = J. K. | last1 = Nimmo | first2 = B. W. | last2 = Lucas | journal = [[Acta Crystallographica Section B]] | year = 1976 | volume = 32 | issue = 7 | pages = 1968–1971 | doi = 10.1107/S0567740876006894 | doi-access = free}}</ref><ref>{{cite journal | title = Growth and single-crystal refinement of phase-III potassium nitrate, KNO<sub>3</sub> | first1 = E. J. | last1 = Freney | first2 = L. A. J. | last2 = Garvie | first3 = T. L. | last3 = Groy | first4 = P. R. | last4 = Buseck | journal = [[Acta Crystallographica Section B]] | year = 2009 | volume = 65 | issue = 6 | pages = 659–663 | doi = 10.1107/S0108768109041019 | pmid = 19923693}}</ref>

[[Sodium nitrate]] is isomorphous with [[calcite]], the most stable form of [[calcium carbonate]], whereas room-temperature potassium nitrate is [[isomorphous]] with [[aragonite]], a slightly less stable [[Polymorphism (materials science)|polymorph]] of calcium carbonate. The difference is attributed to the similarity in size between [[nitrate]] ({{chem2|NO3-}}) and [[carbonate]] ({{chem2|CO3(2-)}}) ions and the fact that the potassium ion ({{chem2|K+}}) is larger than sodium ({{chem2|Na+}}) and calcium ({{chem2|Ca(2+)}}) ions.<ref name="G&E">{{Greenwood&Earnshaw2nd|page=407}}</ref>

In the room-temperature structure of potassium nitrate, each potassium ion is surrounded by 6 nitrate ions. In turn, each nitrate ion is surrounded by 6 potassium ions.<ref name="Adiwidjaja&Pohl" />

{| class="wikitable" style="margin:1em auto; text-align:center;"
|+Room temperature [[crystal structure]] and [[coordination geometry]] of potassium nitrate<ref name="Adiwidjaja&Pohl" />
|-
! Unit cell
! Potassium coordination
! Nitrate coordination
|-
| [[File:Potassium-nitrate-superstructure-unit-cell-3D-bs-17.png|250px]]
| [[File:Potassium-nitrate-xtal-K1-coord-3D-bs-17.png|200px]]
| [[File:Potassium-nitrate-xtal-N1-coord-3D-bs-17.png|150px]]
|}

Potassium nitrate is moderately soluble in water, but its solubility increases with temperature. The aqueous solution is almost neutral, exhibiting [[pH]] 6.2 at {{convert|14|C|F}} for a 10% solution of commercial powder. It is not very [[hygroscopic]], absorbing about 0.03% water in 80% [[relative humidity]] over 50 days. It is insoluble in alcohol and is not poisonous; it can react explosively with [[reducing agents]], but it is not explosive on its own.<ref name=b1/>

===Thermal decomposition===
Between {{convert|550-790|C|F}}, potassium nitrate reaches a temperature-dependent equilibrium with [[potassium nitrite]]:<ref>{{cite journal|title=The Kinetics of the Thermal Decomposition of Potassium Nitrate and of the Reaction between Potassium Nitrite and Oxygen|author=Eli S. Freeman|journal=J. Am. Chem. Soc.|year=1957|volume=79|pages=838–842|doi=10.1021/ja01561a015|issue=4|bibcode=1957JAChS..79..838F }}</ref>
:{{chem2|2 KNO3 ⇌ 2 KNO2 + O2}}

==Uses==
Potassium nitrate has a wide variety of uses, largely as a source of nitrate.

===Nitric acid production===
Historically, [[nitric acid]] was produced by combining sulfuric acid with nitrates such as saltpeter. In modern times this is reversed: nitrates are produced from nitric acid produced via the [[Ostwald process]].

===Oxidizer===
[[File:10. Оксидација на јагленче во стопен калиум нитрат.webm|thumb|right|A demonstration of the oxidation of a piece of [[charcoal]] in molten potassium nitrate]]
The most famous use of potassium nitrate is probably as the oxidizer in [[gunpowder|blackpowder]]. From the most ancient times until the late 1880s, blackpowder provided the explosive power for all the world's firearms. After that time, small arms and large artillery increasingly began to depend on [[cordite]], a [[smokeless powder]]. Blackpowder remains in use today in [[black powder rocket motor]]s, but also in combination with other fuels like sugars in "[[rocket candy]]" (a popular amateur rocket propellant). It is also used in fireworks such as [[smoke bomb]]s.<ref>[http://www.galleries.com/minerals/carbonat/niter/niter.htm Amthyst Galleries, Inc] {{webarchive|url=https://web.archive.org/web/20081104110741/http://www.galleries.com/minerals/carbonat/niter/niter.htm |date=2008-11-04}}. Galleries.com. Retrieved on 2012-03-07.</ref> It is also added to cigarettes to maintain an even burn of the tobacco<ref>[http://tobaccodocuments.org/product_design/00382055-2062.html Inorganic Additives for the Improvement of Tobacco] {{webarchive|url=https://web.archive.org/web/20071101110019/http://tobaccodocuments.org/product_design/00382055-2062.html |date=2007-11-01}}, TobaccoDocuments.org</ref> and is used to ensure complete combustion of [[paper cartridge]]s for cap and ball revolvers.<ref>{{cite book |author=Kirst, W.J. |title=Self Consuming Paper Cartridges for the Percussion Revolver |place=Minneapolis, Minnesota |publisher=Northwest Development Co. |year=1983}}</ref> It can also be heated to several hundred degrees to be used for [[Bluing (steel)#Niter bluing|niter bluing]], which is less durable than other forms of protective oxidation, but allows for specific coloration of steel parts, such as screws, pins, and other small parts of firearms.

===Meat processing===
Potassium nitrate has been a common ingredient of salted meat since [[Antiquity of humanity|antiquity]]<ref>{{Cite journal|last1=Binkerd|first1=E. F|last2=Kolari|first2=O. E|date=1975-01-01|title=The history and use of nitrate and nitrite in the curing of meat|journal=Food and Cosmetics Toxicology|volume=13|issue=6|pages=655–661|doi=10.1016/0015-6264(75)90157-1|issn=0015-6264|pmid=1107192}}</ref> or the [[Middle Ages]].<ref>[https://web.archive.org/web/20031223155710/http://www.uwex.edu/ces/flp/meatscience/sausage.html "Meat Science"], University of Wisconsin. uwex.edu.</ref> The widespread adoption of nitrate use is more recent and is linked to the development of large-scale meat processing.<ref name="auto1" /> The use of potassium nitrate has been mostly discontinued because it gives slow and inconsistent results compared with [[sodium nitrite]] preparations such as "Prague powder" or pink "[[curing salt]]". Even so, potassium nitrate is still used in some food applications, such as salami, dry-cured ham, [[charcuterie]], and (in some countries) in the [[brine]] used to make [[corned beef]] (sometimes together with sodium nitrite).<ref>[http://www.foodnetwork.com/food/recipes/recipe/0,,FOOD_9936_36271,00.html Corned Beef] {{webarchive|url=https://web.archive.org/web/20080319080839/http://www.foodnetwork.com/food/recipes/recipe/0,,FOOD_9936_36271,00.html |date=2008-03-19}}, Food Network</ref> In the Shetland Islands (UK) it is used in the curing of mutton to make [[reestit mutton]], a local delicacy.<ref>{{Cite book |url=https://books.google.com/books?id=CeF0AQAAQBAJ&q=reestit+mutton |title=A Year In A Scots Kitchen |last=Brown |first=Catherine |date=2011-11-14 |publisher=Neil Wilson Publishing Ltd |isbn=9781906476847 |language=en}}</ref> When used as a food additive in the European Union,<ref>UK Food Standards Agency: {{cite web |url=http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist |title=Current EU approved additives and their E Numbers |access-date=2011-10-27 |url-status=live |archive-url=https://web.archive.org/web/20101007124435/http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist |archive-date=2010-10-07}}</ref> the compound is referred to as [[E number|E252]]; it is also approved for use as a food additive in the United States<ref>US Food and Drug Administration: {{cite web |url=https://www.fda.gov/Food/FoodIngredientsPackaging/FoodAdditives/ucm191033.htm#ftnT |title=Listing of Food Additives Status Part II |website=[[Food and Drug Administration]] |access-date=2011-10-27 |url-status=dead |archive-url=https://web.archive.org/web/20111108002304/https://www.fda.gov/Food/FoodIngredientsPackaging/FoodAdditives/ucm191033.htm#ftnT |archive-date=2011-11-08}}</ref> and Australia and New Zealand<ref>Australia New Zealand Food Standards Code {{cite web |url=http://www.comlaw.gov.au/Details/F2011C00827 |title=Standard 1.2.4 – Labelling of ingredients |date=8 September 2011 |access-date=2011-10-27}}</ref> (where it is listed under its [[List of food additives, Codex Alimentarius|INS number]] 252).<ref name=b1/>

====Possible cancer risk====
Since October 2015, [[World Health Organization|WHO]] classifies processed meat as Group 1 carcinogen (based on epidemiological studies, convincingly [[Carcinogenesis|carcinogenic]] to humans).<ref>{{Cite web |title=Cancer: Carcinogenicity of the consumption of red meat and processed meat |url=https://www.who.int/news-room/questions-and-answers/item/cancer-carcinogenicity-of-the-consumption-of-red-meat-and-processed-meat |access-date=2023-12-29 |website=www.who.int |language=en}}</ref>

In April 2023 the French Court of Appeals of Limoges confirmed that food-watch NGO Yuka was legally legitimate in describing Potassium Nitrate [[E number#E200–E299|E249 to E252]] as a "cancer risk", and thus rejected an appeal by the French {{lang|fr|[[charcuterie]]}} industry against the organisation.<ref>{{cite news |title=Nitrites et jambons "cancérogènes" : nouvelle victoire en appel de Yuka contre un industriel de la charcuterie |trans-title=Nitrites and "carcinogenic" hams: Yuka's new appeal victory against a charcuterie manufacturer |work=Marianne |first=Thomas |last=Rabino |date=13 April 2023 |language=fr |quote=Et ce, en dépit de la multiplicité des avis scientifiques, comme celui du Centre international de recherche sur le cancer, classant ces mêmes additifs, connus sous le nom de E249, E250, E251, E252, parmi les « cancérogènes probables », auxquels la Ligue contre le cancer attribue près de 4 000 cancers colorectaux par an. |trans-quote=And this, despite the multiplicity of scientific opinions, such as that of the International Agency for Research on Cancer, classifying these same additives, known as E249, E250, E251, E252, among the "probable carcinogens", to which the League Against Cancer attributes nearly 4,000 colorectal cancers per year.}}</ref>

===Fertilizer===
Potassium nitrate is used in [[fertilizer]]s as a source of nitrogen and potassium – two of the [[Plant nutrition|macronutrients]] for plants. When used by itself, it has an [[NPK rating]] of 13-0-44.<ref>[http://fieldcrop.msu.edu/uploads/documents/e0896.pdf Michigan State University Extension Bulletin E-896: N-P-K Fertilizers] {{webarchive|url=https://web.archive.org/web/20151224052500/http://fieldcrop.msu.edu/uploads/documents/e0896.pdf |date=2015-12-24}}</ref><ref>{{cite book|title=Environmental Impact of Fertilizer on Soil and Water|date=2004|page=40|url=https://books.google.com/books?id=v_PwAAAAMAAJ|isbn=9780841238114|last1=Hall|first1=William L|last2=Robarge|first2=Wayne P|last3=Meeting|first3=American Chemical Society|publisher=American Chemical Society |url-status=live|archive-url=https://web.archive.org/web/20180127195831/https://books.google.com/books?id=v_PwAAAAMAAJ|archive-date=2018-01-27}}</ref>

===Pharmacology===
* Used in some [[toothpaste]]s for [[Dentine hypersensitivity|sensitive teeth]].<ref>{{cite web|title=Sensodyne Toothpaste for Sensitive Teeth |date=2008-08-03 |url=http://us.sensodyne.com/products_freshmint.aspx |access-date=2008-08-03 |url-status=dead |archive-url=https://web.archive.org/web/20070807010449/http://us.sensodyne.com/products_freshmint.aspx |archive-date=August 7, 2007}}</ref> It has been used since 1980, although the efficacy is not strongly supported by the literature.<ref>{{cite journal|pmid=16803826|url=http://www.ufpi.br/subsiteFiles/ppgo/arquivos/files/Orchardson_&_Gillam_2006_Manejo_da_Hipersensibilidade_Dentinaria.pdf|year=2006|author1=R. Orchardson|author2=D. G. Gillam|name-list-style=amp|title=Managing dentin hypersensitivity|volume=137|issue=7|pages=990–8; quiz 1028–9|journal=Journal of the American Dental Association|doi=10.14219/jada.archive.2006.0321|url-status=dead|archive-url=https://web.archive.org/web/20130729082456/http://www.ufpi.br/subsiteFiles/ppgo/arquivos/files/Orchardson_%26_Gillam_2006_Manejo_da_Hipersensibilidade_Dentinaria.pdf|archive-date=2013-07-29|quote=The efficacy of potassium nitrate to reduce DH, however, is not supported strongly by the literature}}</ref><ref>{{cite journal|url=http://sciencelinks.jp/j-east/article/200315/000020031503A0361500.php|title=The Effect of Potassium Nitrate and Silica Dentifrice in the Surface of Dentin|journal=Japanese Journal of Conservative Dentistry|volume=46|issue=2|pages=240–247|year=2003|author=Enomoto, K|display-authors=etal|url-status=dead|archive-url=https://web.archive.org/web/20100111220400/http://sciencelinks.jp/j-east/article/200315/000020031503A0361500.php|archive-date=2010-01-11}}</ref>
* Used historically to treat asthma.<ref>{{cite book|title=Asthma, presenting an exposition of the nonpassive expiration theory|author=Orville Harry Brown|year=1917|publisher=C.V. Mosby company|page=[https://archive.org/details/asthmapresenting00brow/page/277 277]|url=https://archive.org/details/asthmapresenting00brow}}</ref> Used in some toothpastes to relieve asthma symptoms.<ref>{{cite news|author=Joe Graedon|title='Sensitive' toothpaste may help asthma|url=http://www.chicagotribune.com/health/sc-health-0512-pharm-20100512-11,0,4146905.story|access-date=June 18, 2012|newspaper=The Chicago Tribune|date=May 15, 2010|url-status=dead|archive-url=https://web.archive.org/web/20110916071338/http://www.chicagotribune.com/health/sc-health-0512-pharm-20100512-11,0,4146905.story|archive-date=September 16, 2011}}</ref>
* Used in Thailand as main ingredient in kidney tablets to relieve the symptoms of [[cystitis]], [[pyelitis]] and [[urethritis]].<ref>{{cite web|url=http://www2.fda.moph.go.th/exporters/select/eng/drug/dgexp111e.asp?dgnmt=%C2%D2%E0%C1%E7%B4+%E2%AB%E2%C3%A4%D4%B4%B9%D5%E8&lcnsid=1162&lcnscd=2506&lctnmcd=2392&lctdtnmcd=&lctcd=10280266&lcntype=%BC%C21+&lcnno=5000002&rctype=2A%20&rcno=5000163&dgnmoth=ZORO+KIDNEY+TABLETS&dgtype=2&ndrug=2&typecd=1|title=Local manufactured drug registration for human (combine) – Zoro kidney tablets|website=fda.moph.go.th|location=Thailand|quote=Potassium nitrate 60mg|url-status=dead|archive-date=August 8, 2014|archive-url=https://web.archive.org/web/20140808045035/http://www2.fda.moph.go.th/exporters/select/eng/drug/dgexp111e.asp?dgnmt=%C2%D2%E0%C1%E7%B4+%E2%AB%E2%C3%A4%D4%B4%B9%D5%E8&lcnsid=1162&lcnscd=2506&lctnmcd=2392&lctdtnmcd=&lctcd=10280266&lcntype=%BC%C21+&lcnno=5000002&rctype=2A%20&rcno=5000163&dgnmoth=ZORO+KIDNEY+TABLETS&dgtype=2&ndrug=2&typecd=1}}</ref>
* Combats high blood pressure and was once used as a [[hypotensive]].<ref>{{cite journal|title=On the physiological action of potassium nitrite|author=Reichert ET.|journal=Am. J. Med. Sci.|year=1880|volume=80|pages=158–180|doi=10.1097/00000441-188007000-00011}}</ref>

===Other uses===
* Used as an [[electrolyte]] in a [[salt bridge]].
* Active ingredient of [[condensed aerosol fire suppression]] systems. When burned with the [[free radical]]s of a fire's flame, it produces [[potassium carbonate]].<ref>{{cite web|url=https://www.nist.gov/el/fire_research/upload/R0000245.pdf|title=The evaluation of non-pyrotechnically generated aerosols as fire suppressants|author1=Adam Chattaway|author2=Robert G. Dunster|author3=Ralf Gall|author4=David J. Spring|publisher=United States National Institute of Standards and Technology ([[National Institute of Standards and Technology|NIST]])|url-status=live|archive-url=https://web.archive.org/web/20130729080813/http://www.nist.gov/el/fire_research/upload/R0000245.pdf|archive-date=2013-07-29}}</ref>
* Works as an aluminium cleaner.
* Component (usually about 98%) of some [[tree stump]] removal products. It accelerates the natural [[decomposition]] of the stump by supplying nitrogen for the [[fungi]] attacking the [[wood]] of the stump.<ref>{{cite web |url=http://www.aces.edu/homegarden/news/archives/003560.php|archive-url=https://web.archive.org/web/20120323054236/http://www.aces.edu/homegarden/news/archives/003560.php
| publisher =[[Alabama Cooperative Extension System]]|author=Stan Roark|title=Stump Removal for Homeowners|archive-date=March 23, 2012|date=February 27, 2008}}</ref>
* In [[heat treatment]] of metals as a medium temperature molten salt bath, usually in combination with sodium nitrite. A similar bath is used to produce a durable blue/black finish typically seen on firearms. Its [[oxidizing]] quality, water solubility, and low cost make it an ideal short-term [[rust inhibitor]].<ref>{{cite web|url=http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN/6228283|title=Aqueous corrosion inhibitor Note. This patent cites potassium nitrate as a minor constituent in a complex mix. Since rust is an oxidation product, this statement requires justification.|publisher=United States Patent|id=6,228,283|author1=David E. Turcotte|author2=Frances E. Lockwood|date=May 8, 2001|url-status=live|archive-url=https://web.archive.org/web/20180127195832/http://patft.uspto.gov/netacgi/nph-Parser?Sect2=PTO1&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&d=PALL&RefSrch=yes&Query=PN%2F6228283|archive-date=January 27, 2018}}</ref>
* In [[Chemically strengthened glass|glass toughening]]: molten potassium nitrate bath is used to increase glass strength and scratch-resistance.<ref>{{Cite web |title=Chemical Toughening of Customer Owned Glass - TILSE Yacht Glazing |url=https://www.tilse.com/chemical-toughening/#:~:text=The%20glass%20is%20submerged%20in,+)%20from%20the%20salt%20bath. |access-date=2025-01-17 |website=TILSE GmbH |language=en}}</ref>
* To induce flowering of [[mango]] trees in the Philippines.<ref>{{cite web|url=http://www.wipo.int/wipo_magazine/en/2008/03/article_0001.html|title=The Scientist, the Patent and the Mangoes – Tripling the Mango Yield in the Philippines|publisher=United Nations World Intellectual Property Organization ([[World Intellectual Property Organization|WIPO]])|work=WIPO Magazine|author=Elizabeth March| date=June 2008|archive-date=25 August 2012|archive-url=https://web.archive.org/web/20120825204717/http://www.wipo.int/wipo_magazine/en/2008/03/article_0001.html| url-status =live}}</ref><ref>{{cite web|url=http://beta.searca.org/searca/index.php/news/723-filipino-scientist-garners-2011-dioscoro-l-umali-award|title=Filipino scientist garners 2011 Dioscoro L. Umali Award
| publisher =Southeast Asian Regional Center for Graduate Study and Research in Agriculture ([[Southeast Asian Regional Center for Graduate Study and Research in Agriculture|SEARCA]])
| archive-url =https://web.archive.org/web/20111130182054/http://beta.searca.org/searca/index.php/news/723-filipino-scientist-garners-2011-dioscoro-l-umali-award|archive-date=30 November 2011}}</ref>
* Thermal storage medium in [[power generation]] systems. Sodium and potassium nitrate salts are stored in a molten state with the [[solar energy]] collected by the [[heliostat]]s at the [[Gemasolar Thermosolar Plant]]. [[wikt:ternary|Ternary]] [[Salt (chemistry)|salts]], with the addition of [[calcium nitrate]] or [[lithium nitrate]], have been found to improve the heat storage capacity in the molten salts.<ref>{{cite web|url=http://www.estelasolar.eu/fileadmin/ESTELAdocs/documents/powerplants/Gemasolar/Gemasolar_Torresol.pdf|title=Gemasolar, The First Tower Thermosolar Commercial Plant With Molten Salt Storage System|author1=Juan Ignacio Burgaleta|author2=Santiago Arias|author3=Diego Ramirez|publisher=[[Torresol Energy]]|access-date=7 March 2012|archive-url=https://web.archive.org/web/20120309085029/http://www.estelasolar.eu/fileadmin/ESTELAdocs/documents/powerplants/Gemasolar/Gemasolar_Torresol.pdf|archive-date=9 March 2012|type=Press Release|url-status=dead}}</ref>
* As a source of potassium ions for exchange with sodium ions in [[chemically strengthened glass]].
* As an oxidizer in model rocket fuel called [[Rocket candy]].
* As a constituent in homemade [[smoke bomb]]s.<ref>{{Cite web |title=How to Make the Ultimate Colored Smoke Bomb |url=https://www.thoughtco.com/ultimate-colored-smoke-bomb-605967 |access-date=2023-10-18 |website=ThoughtCo |language=en}}</ref>

==In folklore and popular culture==
Potassium nitrate was once thought to induce [[impotence]], and is still rumored to be in institutional food (such as military fare). There is no scientific evidence for such properties.<ref>{{cite web|url=http://www.straightdope.com/classics/a3_221.html|title=The Straight Dope: Does saltpeter suppress male ardor?|date=1989-06-16|access-date=2007-10-19|url-status=live|archive-url=https://web.archive.org/web/20071011053456/http://www.straightdope.com/classics/a3_221.html|archive-date=2007-10-11}}</ref><ref>{{cite book |author1= Richard E. Jones |author2= Kristin H. López |name-list-style= amp |title= Human Reproductive Biology, Third Edition |publisher= [[Elsevier]]/[[Academic Press]] |year= 2006 |page= 225 |url= https://books.google.com/books?id=pfiZfui2XLIC&pg=PA225 |isbn= 978-0-12-088465-0 |url-status= live |archive-url= https://web.archive.org/web/20160501084227/https://books.google.com/books?id=pfiZfui2XLIC&pg=PA225 |archive-date= 2016-05-01}}</ref> In ''[[Bank Shot]]'', El ([[Joanna Cassidy]]) propositions Walter Ballantine ([[George C. Scott]]), who tells her that he has been fed saltpeter in prison.{{Citation needed|date=August 2024}} In ''[[One Flew Over the Cuckoo's Nest (film)|One Flew Over the Cuckoo's Nest]]'', Randle is asked by the nurses to take his medications, but not knowing what they are, he mentions he does not want anyone to "slip me saltpeter". He then proceeds to imitate the motions of masturbation.

In ''[[1776 (musical)|1776]]'', John Adams asks his wife Abigail to make saltpeter for the Continental Army. She, eventually, is able to do so in exchange for pins for sewing.<ref>{{Cite web|url=https://ew.com/article/2014/07/04/watch-1776-4th-of-july/|title=10 reasons true Americans should watch '1776' this 4th of July|website=EW.com|language=en|access-date=2019-08-01}}</ref>

In the ''[[Star Trek]]'' episode "[[Arena (Star Trek: The Original Series)|Arena]]", [[James T. Kirk|Captain Kirk]] injures a [[gorn]] using a rudimentary cannon that he constructs using potassium nitrate as a key ingredient of [[gunpowder]].{{Citation needed|date=August 2024}}

In ''[[21 Jump Street (film)|21 Jump Street]]'', Jenko, played by [[Channing Tatum]], gives a rhyming presentation about potassium nitrate for his chemistry class.{{Citation needed|date=August 2024}}

In ''[[Eating Raoul]]'', Paul hires a [[dominatrix]] to impersonate a nurse and trick Raoul into consuming saltpeter in a ploy to reduce his sexual appetite for his wife.{{Citation needed|date=August 2024}}

In ''[[The Simpsons]]'' episode "[[El Viaje Misterioso de Nuestro Jomer (The Mysterious Voyage of Our Homer)]]", Mr. Burns is seen pouring saltpeter into his chili entry, titled Old Elihu's Yale-Style Saltpeter Chili.{{Citation needed|date=August 2024}}

In the [[Sharpe (novel series)|''Sharpe'' novel series]] by [[Bernard Cornwell]], numerous mentions are made of an advantageous supply of saltpeter from India being a crucial component of British military supremacy in the Napoleonic Wars. In ''Sharpe's Havoc'', the French Captain Argenton laments that France needs to scrape its supply from [[cesspit]]s.{{Citation needed|date=August 2024}}

In the ''[[Dr. Stone]]'' anime and manga series, the struggle for control over a natural saltpeter source from guano features prominently in the plot.{{Citation needed|date=August 2024}}

In the farming lore from the [[Corn Belt]] of the 1800s, drought-killed corn<ref>{{Citation|last1= Krug| first1= E.C.| last2= Hollinger| first2= S.E.| year = 2003| title = Identification of factors that aid carbon sequestration in Illinois agricultural systems| publisher = Illinois State Water Survey, Atmospheric Environment Section| publication-place = Champaign, Illinois| pages= 27–28| url= https://www.isws.illinois.edu/pubdoc/CR/ISWSCR2003-02.pdf
| access-date = 2022-03-13}}</ref> in manured fields could accumulate saltpeter to the extent that upon opening the stalk for examination it would "fall as a fine powder upon the table".<ref>{{Citation| last= Mayo| first= N.S.| year= 1895| title= Cattle poisoning by nitrate of potash| publisher= Kansas State Agricultural College| publication-place = Manhattan| page= 5| url= https://www.ksre.k-state.edu/historicpublications/pubs/SB049.pdf| access-date = 2022-03-13}}</ref>

In the Slovenian short story [[Martin Krpan|Martin Krpan from Vrh pri Sveti Trojici]], the titular character and Slovene folk hero Martin Krpan illegally smuggles "English salt" for a living. The exact nature of "English salt" is a matter of debate, but it may have been a euphemism for potassium nitrate (saltpeter) due to its role in manufacturing [[gunpowder]].{{Citation needed|date=November 2024}}

In [[Dexter: Original Sin]]'s first episode, Dexter's first victim uses potassium nitrate to kill her victims.

In [[Gabriel García Márquez]]’s novella [[Chronicle of a Death Foretold]], the character Bayardo San Román is described as having “a skin slowly roasted by saltpeter”.

==See also==
*[[History of gunpowder]]
*[[Humberstone and Santa Laura Saltpeter Works]]
*[[Niter]], a mineral form of potassium nitrate
*[[Nitratine]]
*[[Nitrocellulose]]
*[[Potassium perchlorate]]

==References==
{{reflist}}

==Bibliography==
*{{cite journal |last1=Barnum |first1=Dennis W. |title=Some History of Nitrates |journal=Journal of Chemical Education |volume=80 |issue=12 |page=1393 |doi=10.1021/ed080p1393 |date=December 2003|bibcode=2003JChEd..80.1393B}}
* David Cressy. ''Saltpeter: The Mother of Gunpowder'' (Oxford University Press, 2013) 237 pp [https://www.h-net.org/reviews/showrev.php?id=39062 online review by Robert Tiegs] 
*Alan Williams. "The production of saltpeter in the Middle Ages", ''[[Ambix]]'', 22 (1975), pp.&nbsp;125–33. [[Maney Publishing]], ISSN 0002-6980.

==External links==
{{wikiquote}}
* {{cite EB9 |wstitle = Saltpetre |volume= XXI | page=235 |short=1}}
*[http://www.inchem.org/documents/icsc/icsc/eics0184.htm International Chemical Safety Card 018402216]

{{Potassium compounds}}
{{nitrates}}
{{Salt topics}}

{{Authority control}}

{{DEFAULTSORT:Potassium Nitrate}}
[[Category:Gunpowder]]
[[Category:Inorganic fertilizers]]
[[Category:Nitrates]]
[[Category:Potassium compounds]]
[[Category:Preservatives]]
[[Category:Pyrotechnic oxidizers]]
[[Category:E-number additives]]