Potassium nitrate is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

. This

alkali metal nitrate Alkali metal nitrates are chemical compounds consisting of an alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Lat ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

is also known as Indian saltpetre (large deposits of which were historically mined in

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

). It is an

ionic salt In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively ch ...

potassium ion Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmospher ...

s K⁺ and

nitrate ion Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insoluble ...

s NO₃⁻, and is therefore an

. It occurs in nature as a mineral,

niter Niter or nitre is the mineral form of potassium nitrate, KNO3. It is a soft, white, highly soluble mineral found primarily in arid climates or cave deposits. Historically, the term ''niter'' was not well differentiated from natron, both of w ...

(or ''nitre'' in the UK). It is a source of

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

, and nitrogen was named after niter. Potassium nitrate is one of several nitrogen-containing compounds collectively referred to as saltpeter (or ''saltpetre'' in the UK). Major uses of potassium nitrate are in

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

s, tree stump removal,

rocket propellant Rocket propellant is the reaction mass of a rocket. This reaction mass is ejected at the highest achievable velocity from a rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propuls ...

s and

firework Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices in ...

s. It is one of the major constituents of

gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). ...

(black powder). In

processed meat Processed meat is considered to be any meat which has been modified in order to either improve its taste or to extend its shelf life. Methods of meat processing include salting, curing, fermentation, smoking, and/or the addition of chemical pre ...

s, potassium nitrate reacts with

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...

and

myoglobin Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the cardiac and skeletal muscle tissue of vertebrates in general and in almost all mammals. Myoglobin is distantly related to hemoglobin. Compared to hemoglobin, myoglobi ...

generating a red color.

Etymology

Potassium nitrate, because of its early and global use and production, has many names. Hebrew and Egyptian words for it had the consonants n-t-r, indicating likely 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'', specifically Indian saltpetre (sodium nitrate is chile saltpetre) and later as ''nitrate of potash,'' as the chemistry of the compound was more fully understood. The Arabs called it "Chinese snow" ( ar, ثلج الصين '). It was called "Chinese salt" by the Iranians/Persians or "salt from Chinese salt marshes" ( fa, نمک شوره چينی ').

Historical production

From mineral sources

In Ancient India, saltpeter manufacturers formed the Nuniya caste. Saltpeter finds mention in Kautilya's

Arthashastra The ''Arthashastra'' ( sa, अर्थशास्त्रम्, ) is an Ancient Indian Sanskrit treatise on statecraft, political science, economic policy and military strategy. Kautilya, also identified as Vishnugupta and Chanakya, is ...

(compiled 300BC - 300AD), which mentions using its poisonous smoke as a weapon of war, 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 Hasan al-Rammah (, died 1295) was a Syrian Arab chemist and engineer during the Mamluk Sultanate who studied gunpowders and explosives, and sketched prototype instruments of warfare, including the first torpedo. Al-Rammah called his early torpedo " ...

Syria Syria ( ar, سُورِيَا or سُورِيَة, translit=Sūriyā), officially the Syrian Arab Republic ( ar, الجمهورية العربية السورية, al-Jumhūrīyah al-ʻArabīyah as-Sūrīyah), is a Western Asian country loc ...

in his book ''al-Furusiyya wa al-Manasib al-Harbiyya'' (''The Book of 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 Potassium carbonate is the inorganic compound with the formula K2 CO3. It is a white salt, which is soluble in water. It is deliquescent, often appearing as a damp or wet solid. Potassium carbonate is mainly used in the production of soap and gl ...

(in the form of

wood ash Wood ash is the powdery residue remaining after the combustion of wood, such as burning wood in a fireplace, bonfire, or an industrial power plant. It is largely composed of calcium compounds along with other non-combustible trace elements presen ...

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. 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. At least as far back as 1845,

nitratite Nitratine or nitratite, also known as cubic niter (UK: nitre), soda niter or Chile saltpeter (UK: Chile saltpetre), is a mineral, the naturally occurring form of sodium nitrate, NaNO3. Chemically it is the sodium analogue of saltpeter. Nitratine ...

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 Guano (Spanish from qu, wanu) is the accumulated excrement of seabirds or bats. As a manure, guano is a highly effective fertilizer due to the high content of nitrogen, phosphate, and potassium, all key nutrients essential for plant growth. ...

in caves. 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 Laos (, ''Lāo'' )), officially the Lao People's Democratic Republic ( Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ, French: République démocratique populaire lao), is a socialist ...

for the manufacture of gunpowder for ''Bang Fai'' rockets.

Nitraries

Potassium nitrate is produced in a ''nitrary''. The process involved burial of excrements (human or animal) in a field beside the nitraries, watering them and waiting until leaching allowed saltpeter to come to the ground surface by

efflorescence In chemistry, efflorescence (which means "to flower out" in French) is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or ...

. Operators then gathered the resulting powder and transported it to be concentrated by

ebullition Boiling is the rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point, the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding atmosphere. Ther ...

in the boiler plant. Besides " 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." In 1561,

Elizabeth I of England Elizabeth I (7 September 153324 March 1603) was List of English monarchs, Queen of England and List of Irish monarchs, Ireland from 17 November 1558 until her death in 1603. Elizabeth was the last of the five House of Tudor monarchs and is ...

at war with

Philip II of Spain Philip II) in Spain, while in Portugal and his Italian kingdoms he ruled as Philip I ( pt, Filipe I). (21 May 152713 September 1598), also known as Philip the Prudent ( es, Felipe el Prudente), was King of Spain from 1556, King of Portugal from ...

, became unable to import the saltpeter (of which the

Kingdom of England The Kingdom of England (, ) was a sovereign state on the island of Great Britain from 12 July 927, when it emerged from various Anglo-Saxon kingdoms, until 1 May 1707, when it united with Scotland to form the Kingdom of Great Britain. On 1 ...

had no home production), and had to pay "300 pounds gold" to the German captain Gerrard Honrik for the manual "Instructions for making salpeter to growe" (the secret of the "Feuerwerkbuch" -the nitraries-).

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 wait for soil microbes to convert amino-nitrogen into nitrates by

nitrification ''Nitrification'' is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of amm ...

. 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. The Confederate side of the American Civil War had a significant shortage of saltpeter. As a result, the

Nitre and Mining Bureau The Confederate Nitre and Mining Bureau was a civilian government bureau to provide the Confederate States of America with needed materials such as copper, iron, lead, saltpeter, sulfur, zinc, and other metals. The Bureau oversaw civilian contracts ...

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. Perhaps the most exhaustive discussion of the niter-bed production is the 1862 LeConte text. He was writing with the express purpose of increasing production in the

Confederate States The Confederate States of America (CSA), commonly referred to as the Confederate States or the Confederacy was an unrecognized breakaway republic in the Southern United States that existed from February 8, 1861, to May 9, 1865. The Confeder ...

to support their needs during the

American Civil War The American Civil War (April 12, 1861 – May 26, 1865; also known by other names) was a civil war in the United States. It was fought between the Union ("the North") and the Confederacy ("the South"), the latter formed by states th ...

. 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

Turgot Turgot may refer to: * Turgot of Durham ( – 1115), Prior of Durham and Bishop of St Andrews * Michel-Étienne Turgot (1690–1751), mayor of Paris * Anne Robert Jacques Turgot (1727–1781), French economist and statesman * Louis Félix Étienn ...

and

Lavoisier Antoine-Laurent de Lavoisier ( , ; ; 26 August 17438 May 1794),
CNRS (

French Revolution The French Revolution ( ) was a period of radical political and societal change in France that began with the Estates General of 1789 and ended with the formation of the French Consulate in November 1799. Many of its ideas are considere ...

. Niter-beds were prepared by mixing

manure Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the fertility of soil by adding organic matter and nutri ...

with either mortar or wood ashes, common earth and organic materials such as

straw Straw is an agricultural byproduct consisting of the dry stalks of cereal plants after the grain and chaff have been removed. It makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has a number ...

to give porosity to a compost pile typically high, wide, and long. The heap was usually under a cover from the rain, kept moist with

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excretion, excreted from the body through the urethra. Cel ...

, turned often to accelerate the decomposition, then finally leached with water after approximately one year, to remove the soluble

calcium nitrate Calcium nitrate, also called ''Norgessalpeter'' (Norwegian salpeter), is an inorganic compound with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhyd ...

which was then converted to potassium nitrate by filtering through

potash Potash () includes various mined and manufactured salts that contain potassium in water-soluble form.

Swiss method

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 were then converted to potassium nitrate using potash, as above.

From nitric acid

From 1903 until the

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

era, potassium nitrate for black powder and fertilizer was produced on an industrial scale from nitric acid produced using the

Birkeland–Eyde process The Birkeland–Eyde process was one of the competing industrial processes in the beginning of nitrogen-based fertilizer production. It is a multi-step nitrogen fixation reaction that uses electrical arcs to react atmospheric nitrogen (N2) with ox ...

, which used an electric arc to oxidize nitrogen from the air. During World War I the newly industrialized

Haber process The Haber process, also called the Haber–Bosch process, is an artificial nitrogen fixation process and is the main industrial procedure for the production of ammonia today. It is named after its inventors, the German chemists Fritz Haber and C ...

(1913) was combined with the

Ostwald process The Ostwald process is a chemical process used for making nitric acid (HNO3). Wilhelm Ostwald developed the process, and he patented it in 1902. The Ostwald process is a mainstay of the modern chemical industry, and it provides the main raw materia ...

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

Modern production

Potassium nitrate can be made by combining

ammonium nitrate Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...

and

potassium hydroxide Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...

. :NH₄NO₃ (aq) + KOH (aq) → NH₃ (g) + KNO₃ (aq) + H₂O (l) An alternative way of producing potassium nitrate without a by-product of ammonia is to combine ammonium nitrate, found in instant ice packs, and

potassium chloride Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...

, easily obtained as a sodium-free

salt substitute A salt substitute, also known as low-sodium salt, is a low-sodium alternative to edible salt (table salt) marketed to circumvent the risk of high blood pressure and cardiovascular disease associated with a high intake of sodium chloride while main ...

. :NH₄NO₃ (aq) + KCl (aq) → NH₄Cl (aq) + KNO₃ (aq) Potassium nitrate can also be produced by neutralizing

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

with potassium hydroxide. This reaction is highly exothermic. :KOH (aq) + HNO₃ → KNO₃ (aq) + H₂O (l) On industrial scale it is prepared by the double displacement reaction between

sodium nitrate Sodium nitrate is the chemical compound with the formula . This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordinary saltpeter, potassium nitrate. T ...

and potassium chloride. :NaNO₃ (aq) + KCl (aq) → NaCl (aq) + KNO₃ (aq)

Properties

Potassium nitrate has an

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

crystal structure at room temperature, which transforms to a trigonal system at . Potassium nitrate is moderately soluble in water, but its solubility increases with temperature. The aqueous solution is almost neutral, exhibiting pH 6.2 at for a 10% solution of commercial powder. It is not very

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...

, absorbing about 0.03% water in 80%

relative humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

over 50 days. It is insoluble in alcohol and is not poisonous; it can react explosively with

reducing agents In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth meta ...

, but it is not explosive on its own.

Thermal decomposition

Between , potassium nitrate reaches a temperature-dependent equilibrium with

potassium nitrite Potassium nitrite (distinct from potassium nitrate) is the inorganic compound with the chemical formula . It is an ionic salt of potassium ions K+ and nitrite ions NO2−, which forms a white or slightly yellow, hygroscopic crystalline powder that ...

: :2 KNO₃ 2 KNO₂ + O₂

Uses

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

Nitric acid production

Historically,

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

Oxidizer

The most famous use of potassium nitrate is probably as the oxidizer in

blackpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...

. 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 Cordite is a family of smokeless propellants developed and produced in the United Kingdom since 1889 to replace black powder as a military propellant. Like modern gunpowder, cordite is classified as a low explosive because of its slow burni ...

, a

smokeless powder Finnish smokeless powderSmokeless powder is a type of propellant used in firearms and artillery that produces less smoke and less fouling when fired compared to gunpowder ("black powder"). The combustion products are mainly gaseous, compared to a ...

. Blackpowder remains in use today in

black powder rocket motor A black powder rocket motor propels a model rocket using black powder. Black powder rocket propellants consist of charcoal, sulfur, and potassium nitrate. Adjustments can be made to the amount of each component to change the rate at which the black ...

s, but also in combination with other fuels like sugars in "

rocket candy Rocket Candy, or R-Candy, is a type of rocket propellant for model rockets made with sugar as a fuel, and containing an oxidizer. The propellant can be divided into three groups of components: the fuel, the oxidizer, and the additive(s). In the pas ...

" (a popular amateur rocket fuel). It is also used in fireworks such as

smoke bomb A smoke bomb is a firework designed to produce a large amount of smoke upon ignition. History Early Japanese history saw the use of a rudimentary form of the smoke bomb. Explosives were common in Japan during the Mongol invasions of the 13th ...

s. It is also added to cigarettes to maintain an even burn of the tobacco and is used to ensure complete combustion of

paper cartridge A paper cartridge is one of various types of small arms ammunition used before the advent of the metallic cartridge. These cartridges consisted of a paper cylinder or cone containing the bullet, gunpowder, and in some cases, a primer or a lubri ...

s for cap and ball revolvers. It can also be heated to several hundred degrees to be used for niter bluing, which is less durable than other forms of protective oxidation, but allows for specific and often beautiful 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 or the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire a ...

. The widespread adoption of nitrate use is more recent and is linked to the development of large-scale meat processing. The use of potassium nitrate has been mostly discontinued because of slow and inconsistent results compared to

sodium nitrite Sodium nitrite is an inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite ...

compounds such as "Prague powder" or pink "

curing salt Curing salt is used in meat processing to generate a pinkish shade and to extend shelf life. It is both a color agent and a means to facilitate food preservation as it prevents or slows spoilage by bacteria or fungus. Curing salts are generall ...

". Even so, potassium nitrate is still used in some food applications, such as salami, dry-cured ham,

charcuterie Charcuterie ( , also ; ; from french: chair, , flesh, label=none, and french: cuit, , cooked, label=none) is a French term for a branch of cooking devoted to prepared meat products, such as bacon, ham, sausage, terrines, ''galantines'', ''balloti ...

, and (in some countries) in the

brine Brine is a high-concentration solution of salt (NaCl) in water (H2O). In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of that of solutions used for br ...

used to make

corned beef Corned beef, or salt beef in some of the Commonwealth of Nations, is Salt-cured meat, salt-cured brisket of beef. The term comes from the treatment of the meat with large-grained rock salt, also called "corns" of salt. Sometimes, sugar and sp ...

(sometimes together with sodium nitrite). When used as a food additive in the European Union, the compound is referred to as E252; it is also approved for use as a food additive in the United States and Australia and New Zealand (where it is listed under its

INS number The International Numbering System for Food Additives (INS) is a European-based naming system for food additives, aimed at providing a short designation of what may be a lengthy actual name."Class Names and the International Numbering System for Fo ...

252).

Food preparation

In West African cuisine, potassium nitrate (saltpetre) is widely used as a thickening agent in soups and stews such as

okra soup Okra or Okro soup is prepared using the edible green seed pods of the okra flowering plant as a primary ingredient. Other vegetables can be added to the soup as well, such as ewedu, kerenkere, or Ugu leaf. Depending on the specific variant being ...

and

isi ewu ''Isi ewu'' () is a traditional Igbo dish that is made with a goat's head. It is an Igbo soup similar to spicy cow feet (''nkwobi'') except that isi ewu is made up of goat head while the latter is made up of cow foot. Some restaurants choose ...

. It is also used to soften food and reduce cooking time when boiling

beans A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes th ...

and tough meat. Saltpetre is also an essential ingredient in making special porridges, such as ''kunun kanwa'' literally translated from the

Hausa language Hausa (; /; Ajami: ) is a Chadic language spoken by the Hausa people in the northern half of Nigeria, Ghana, Cameroon, Benin and Togo, and the southern half of Niger, Chad and Sudan, with significant minorities in Ivory Coast. Hausa is a member ...

as 'saltpetre porridge'. In the Shetland Islands (UK) it is used in the curing of mutton to make reestit mutton, a local delicacy.

Fertilizer

Potassium nitrate is used in

s as a source of nitrogen and potassium – two of the

macronutrients A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

for plants. When used by itself, it has an

NPK rating Many countries have standardized the labeling of fertilizers to indicate their contents of major nutrients. The most common labeling convention, the NPK or N-P-K label, shows the amounts of the chemical elements nitrogen, phosphorus, and potassi ...

of 13-0-44.

Pharmacology

* Used in some

toothpaste Toothpaste is a paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, a ...

s for sensitive teeth. Recently, the use of potassium nitrate in toothpastes for treating sensitive teeth has increased. * Used historically to treat asthma. Used in some toothpastes to relieve asthma symptoms. * Used in Thailand as main ingredient in kidney tablets to relieve the symptoms of

cystitis A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...

pyelitis Pyelonephritis is inflammation of the kidney, typically due to a bacterial infection. Symptoms most often include fever and flank tenderness. Other symptoms may include nausea, burning with urination, and frequent urination. Complications may i ...

and

urethritis Urethritis is the inflammation of the urethra. The most common symptoms include painful or difficult urination and urethral discharge. It is a commonly treatable condition usually caused by infection with bacteria. This bacterial infection is oft ...

. * Combats high blood pressure and was once used as a

hypotensive Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the dias ...

Other uses

Electrolyte An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon dis ...

in a

salt bridge In electrochemistry, a salt bridge or ion bridge is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell (voltaic cell), a type of electrochemical cell. It maintains electrical neutrality within the int ...

* Active ingredient of

condensed aerosol fire suppression Condensed aerosol fire suppression is a particle-based form of fire extinction. It is similar to dry chemical fire extinction). It employs a fire-extinguishing agent consisting of: very fine solid particles as well as gaseous matter. The cond ...

systems. When burned with the

free radical A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Ailments of unknown cause Biogerontology Biological processes Causes of death Cellular processes Gerontology Life extension Metabo ...

s of a fire's flame, it produces

. * Works as an aluminium cleaner. * Component (usually about 98%) of some

tree stump After a tree has been cut and felled, the stump or tree stump is usually a small remaining portion of the trunk with the roots still in the ground. Stumps may show the age-defining rings of a tree. The study of these rings is known as dendrochrono ...

removal products. It accelerates the natural

decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...

of the stump by supplying nitrogen for the

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

attacking the

wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...

of the stump. * In

heat treatment Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also ...

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 Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

quality, water solubility, and low cost make it an ideal short-term rust inhibitor. * To induce flowering of

mango A mango is an edible stone fruit produced by the tropical tree ''Mangifera indica''. It is believed to have originated in the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South a ...

trees in the Philippines. * Thermal storage medium in

power generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its stor ...

systems. Sodium and potassium nitrate salts are stored in a molten state with the

solar energy Solar energy is radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy (including solar water heating), and solar architecture. It is an essenti ...

collected by the

heliostat A heliostat (from ''helios'', the Greek word for ''sun'', and ''stat'', as in stationary) is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating ...

s at the

Gemasolar Thermosolar Plant Gemasolar is a concentrated solar power plant with a molten salt heat storage system. It is located within the city limits of Fuentes de Andalucía in the province of Seville, Spain. Design and specifications The plant is of the solar power tow ...

Ternary Ternary (from Latin ''ternarius'') or trinary is an adjective meaning "composed of three items". It can refer to: Mathematics and logic * Ternary numeral system, a base-3 counting system ** Balanced ternary, a positional numeral system, useful ...

salts In chemistry, a salt is a chemical compound consisting of an ionic assembly of positively charged cations and negatively charged anions, which results in a compound with no net electric charge. A common example is table salt, with positively cha ...

, with the addition of

lithium nitrate Lithium nitrate is an inorganic compound with the formula LiNO3. It is the lithium salt of nitric acid (an alkali metal nitrate). The salt is deliquescent, absorbing water to form the hydrated form, lithium nitrate trihydrate. Its eutectics are o ...

, have been found to improve the heat storage capacity in the molten salts. * As a source of potassium ions for exchange with sodium ions in

chemically strengthened glass Chemically strengthened glass is a type of glass that has increased strength as a result of a post-production chemical process. When broken, it still shatters in long pointed splinters similar to float glass. For this reason, it is not considered a ...

. * As an oxidizer in model rocket fuel called

Rocket candy Rocket Candy, or R-Candy, is a type of rocket propellant for model rockets made with sugar as a fuel, and containing an oxidizer. The propellant can be divided into three groups of components: the fuel, the oxidizer, and the additive(s). In the pas ...

In folklore and popular culture

Potassium nitrate was once thought to induce

impotence Erectile dysfunction (ED), also called impotence, is the type of sexual dysfunction in which the penis fails to become or stay erect during sexual activity. It is the most common sexual problem in men.Cunningham GR, Rosen RC. Overview of male ...

, and is still rumored to be in institutional food (such as military fare) as an

anaphrodisiac An anaphrodisiac (also antaphrodisiac or antiaphrodisiac) is a substance that quells or blunts the libido. It is the opposite of an aphrodisiac, something that enhances sexual appetite. The word ''anaphrodisiac'' comes from the Greek privative p ...

; however, there is no scientific evidence for such properties. In ''

Bank Shot ''Bank Shot'' is a 1974 heist film directed by Gower Champion and written by Wendell Mayes. It was loosely based upon Donald E. Westlake's 1972 novel of the same name, which was the second book of his " Dortmunder" series. The film stars Geor ...

'', El (

Joanna Cassidy Joanna Cassidy (born Joanna Virginia Caskey, August 2, 1945 Brady, James"In Step With: Joanna Cassidy" ''Miami Herald'', November 25, 1990. Accessed March 14, 2022, via Newspapers.com. "Born: Aug.2, 1944, in Camden, N.J.") is an American actress. ...

) propositions Walter Ballantine (

George C. Scott George Campbell Scott (October 18, 1927 – September 22, 1999) was an American actor, director, and producer who had a celebrated career on both stage and screen. With a gruff demeanor and commanding presence, Scott became known for his port ...

), who tells her that he has been fed saltpeter in prison. "You know why they feed you saltpeter in prison?" Ballantine asks her. She shakes her head no. They kiss. He glances down at his crotch, making a gesture that reveals his body has not responded to her advances, and says, "That's why they feed you saltpeter in prison." In '' 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 reference to its supposed effects as an

. In ''

1776 Events January–February * January 1 – American Revolutionary War – Burning of Norfolk: The town of Norfolk, Virginia is destroyed, by the combined actions of the British Royal Navy and occupying Patriot forces. * January 1 ...

'', 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. In the ''

Star Trek ''Star Trek'' is an American science fiction media franchise created by Gene Roddenberry, which began with the eponymous 1960s television series and quickly became a worldwide pop-culture phenomenon. The franchise has expanded into vari ...

'' episode "

Arena An arena is a large enclosed platform, often circular or oval-shaped, designed to showcase theatre, musical performances, or sporting events. It is composed of a large open space surrounded on most or all sides by tiered seating for spectators ...

Captain Kirk James Tiberius Kirk is a fictional character in the '' Star Trek'' media franchise. Originally played by Canadian actor William Shatner, Kirk first appeared in '' Star Trek'' serving aboard the starship USS ''Enterprise'' as captain. Kirk lea ...

injures a

gorn The Gorn are a fictional extraterrestrial humanoid reptilian species in the American science fiction franchise ''Star Trek''. They first appeared in a 1967 episode of Star Trek: The Original Series, the original series, "Arena (Star Trek: The Or ...

using a rudimentary cannon that he constructs using potassium nitrate as a key ingredient of

. In ''

21 Jump Street ''21 Jump Street'' is an American police procedural television series that aired on the Fox network and in first run syndication from April 12, 1987, to April 27, 1991, with a total of 103 episodes. The series focuses on a squad of youthful-loo ...

'', Jenko, played by

Channing Tatum Channing Matthew Tatum (born April 26, 1980) is an American actor. Tatum made his film debut in the drama ''Coach Carter'' (2005), and had his breakthrough role in the 2006 dance film ''Step Up (film), Step Up''. He gained wider attention for ...

, gives a rhyming presentation about potassium nitrate for his chemistry class. In ''

Eating Raoul ''Eating Raoul'' is a 1982 American black comedy film written, directed by and starring Paul Bartel with Mary Woronov, Robert Beltran, Ed Begley Jr., Buck Henry, and Susan Saiger. It is about a prudish married couple (Bartel and Woronov) who re ...

'', Paul hires a

dominatrix A dominatrix (; ) or femdom is a woman who takes the dominant role in BDSM activities. A dominatrix can be of any sexual orientation, but this does not necessarily limit the genders of her submissive partners. Dominatrices are known for inflic ...

to impersonate a nurse and trick Raoul into consuming saltpeter in a ploy to reduce his sexual appetite for his wife. In ''

The Simpsons ''The Simpsons'' is an American animated sitcom created by Matt Groening for the Fox Broadcasting Company. The series is a satirical depiction of American life, epitomized by the Simpson family, which consists of Homer, Marge, Bart, Lisa, ...

'' episode "

El Viaje Misterioso de Nuestro Jomer (The Mysterious Voyage of Homer) "El Viaje Misterioso de Nuestro Jomer (The Mysterious Voyage of Homer)", () also known as "The Mysterious Voyage of Our Homer", is the ninth episode of the eighth season of the American animated television series ''The Simpsons''. It originally a ...

", Mr. Burns is seen pouring saltpeter into his chili entry, titled Old Elihu's Yale-Style Saltpeter Chili. In the ''Sharpe'' novel series by

Bernard Cornwell Bernard Cornwell (born 23 February 1944) is an English-American author of historical novels and a history of the Waterloo Campaign. He is best known for his novels about Napoleonic Wars rifleman Richard Sharpe. He has also written ''The Saxon ...

, 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 need to scrape their supply from

cesspit A cesspit (or cesspool or soak pit in some contexts) is a term with various meanings: it is used to describe either an underground holding tank (sealed at the bottom) or a soak pit (not sealed at the bottom). It can be used for the temporary co ...

s. In the ''

Dr Stone ''Dr. Stone'' (stylized as ''Dr.STONE'') is a Japanese manga series written by Riichiro Inagaki and illustrated by the South Korean artist Boichi. It was serialized in Shueisha's ''Weekly Shōnen Jump'' from March 2017 to March 2022, wi ...

'' anime and manga series, the struggle for control over a natural saltpeter source from guano features prominently in the plot. In the farming lore from the

Corn Belt The Corn Belt is a region of the Midwestern United States that, since the 1850s, has dominated corn production in the United States. In the United States, ''corn'' is the common word for maize. More generally, the concept of the Corn Belt con ...

of the 1800s, drought-killed corn 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”.

References

Bibliography

* * David Cressy. ''Saltpeter: The Mother of Gunpowder'' (Oxford University Press, 2013) 237 p
online review by Robert Tiegs
*Alan Williams. "The production of saltpeter in the Middle Ages", ''

Ambix ''Ambix'' is a peer-reviewed academic journal on the history of alchemy and chemistry; it was founded in 1936 and has appeared continuously from 1937 to the present, other than from 1939 to 1945 during World War II. It is currently published by the ...

'', 22 (1975), pp. 125–33.

Maney Publishing Maney Publishing was an independent academic publishing company that was taken over by Taylor & Francis in 2015. Maney Publishing specialised in peer-reviewed academic journals in materials science and engineering, the humanities, and health ...

, ISSN 0002-6980.

External links

International Chemical Safety Card 018402216
{{DEFAULTSORT:Potassium Nitrate Gunpowder Inorganic fertilizers Nitrates Potassium compounds Preservatives Pyrotechnic oxidizers E-number additives