Names | |||
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IUPAC name Potassium nitrate | |||
Other names
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Identifiers | |||
3D model (JSmol) | |||
ChEMBL | |||
ChemSpider | |||
ECHA InfoCard | 100.028.926 | ||
EC Number |
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E number | E252 (preservatives) | ||
KEGG | |||
PubChem CID | |||
RTECS number |
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UNII | |||
UN number | 1486 | ||
CompTox Dashboard (EPA) | |||
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Properties | |||
KNO3 | |||
Molar mass | 101.1032 g/mol | ||
Appearance | white solid | ||
Odor | odorless | ||
Density | 2.109 g/cm3 (16 °C) | ||
Melting point | 334 °C (633 °F; 607 K) | ||
Boiling point | 400 °C (752 °F; 673 K) (decomposes) | ||
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Solubility | slightly soluble in ethanol soluble in glycerol, ammonia | ||
Basicity (pKb) | 15.3 [3] | ||
−33.7·10−6 cm3/mol | |||
Refractive index (nD) | 1.335, 1.5056, 1.5604 | ||
Structure | |||
Orthorhombic, Aragonite | |||
Thermochemistry | |||
Heat capacity (C) | 95.06 J/mol K | ||
Std enthalpy of formation (ΔfH⦵298) | −494.00 kJ/mol | ||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards | Oxidant, harmful if swallowed, inhaled, or absorbed on skin. Causes irritation to skin and eye area. | ||
GHS labelling: | |||
H272, H315, H319, H335 | |||
P102, P210, P220, P221, P280 | |||
NFPA 704 (fire diamond) | |||
Flash point | non-flammable (oxidizer) | ||
Lethal dose or concentration (LD, LC): | |||
LD50 (median dose) | 1901 mg/kg (oral, rabbit) 3750 mg/kg (oral, rat) [4] | ||
Safety data sheet (SDS) | ICSC 0184 | ||
Related compounds | |||
Other anions | Potassium nitrite | ||
Other cations | |||
Related compounds | |||
Supplementary data page | |||
Potassium nitrate (data page) | |||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Potassium nitrate is a chemical compound with a sharp, salty, bitter taste and the chemical formula K N O 3. It is a potassium salt of nitric acid. This salt consists of potassium cations K+ and nitrate anions NO−3, and is therefore an alkali metal nitrate. It occurs in nature as a mineral, niter (or nitre outside the US). [5] 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 US). [5]
Major uses of potassium nitrate are in fertilizers, tree stump removal, rocket propellants and fireworks. It is one of the major constituents of gunpowder (black powder). [6] In processed meats, potassium nitrate reacts with hemoglobin and myoglobin generating a red color. [7]
Nitre, or potassium nitrate, because of its early and global use and production, has many names.
As for nitrate, 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, [8] specifically Indian saltpetre (Chilean saltpetre is sodium nitrate [9] ) and later as nitrate of potash, as the chemistry of the compound was more fully understood.
The Arabs called it "Chinese snow" (Arabic : ثلج الصين, romanized: thalj al-ṣīn) as well as bārūd (بارود), a term of uncertain origin that later came to mean gunpowder. It was called "Chinese salt" by the Iranians/Persians [10] [11] [12] or "salt from Chinese salt marshes" (Persian : نمک شوره چينیnamak shūra chīnī). [13] : 335 [14] 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.
In Mauryan India saltpeter manufacturers formed the Nuniya & Labana caste. [15] Saltpeter finds mention in Kautilya's Arthashastra (compiled 300BC – 300AD), which mentions using its poisonous smoke as a weapon of war, [16] 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 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 ashes) 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. [17] 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. [18]
At least as far back as 1845, nitratite deposits were exploited in Chile and California.
Major natural sources of potassium nitrate were the deposits crystallizing from cave walls and the accumulations of bat guano in caves. [19] 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 Bang Fai rockets. [20]
Calcium nitrate, or lime saltpetre, was discovered on the walls of stables, from the urine of barnyard animals. [9]
Potassium nitrate was produced in a nitrary or "saltpetre works". [21] 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. [22] [23]
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". [13] : 89, 311 [24]
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-). [25]
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. [26]
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. [27]
Perhaps the most exhaustive discussion of the niter-bed production is the 1862 LeConte text. [28] 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.
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 or wood ashes, common earth and organic materials such as straw to give porosity to a compost pile typically 4 feet (1.2 m) high, 6 feet (1.8 m) wide, and 15 feet (4.6 m) long. [28] The heap was usually under a cover from the rain, kept moist with urine, turned often to accelerate the decomposition, then finally leached with water after approximately one year, to remove the soluble calcium nitrate which was then converted to potassium nitrate by filtering through potash.
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. [29]
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).
Potassium nitrate can be made by combining ammonium nitrate and potassium hydroxide.
An alternative way of producing potassium nitrate without a by-product of ammonia is to combine ammonium nitrate, found in instant ice packs, [30] and potassium chloride, easily obtained as a sodium-free salt substitute.
Potassium nitrate can also be produced by neutralizing nitric acid with potassium hydroxide. This reaction is highly exothermic.
On industrial scale it is prepared by the double displacement reaction between sodium nitrate and potassium chloride.
Potassium nitrate has an orthorhombic crystal structure at room temperature, [31] which transforms to a trigonal system at 128 °C (262 °F). On cooling from 200 °C (392 °F), another trigonal phase forms between 124 °C (255 °F) and 100 °C (212 °F). [32] [33]
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 polymorph of calcium carbonate. The difference is attributed to the similarity in size between nitrate (NO−3) and carbonate (CO2−3) ions and the fact that the potassium ion (K+) is larger than sodium (Na+) and calcium (Ca2+) ions. [34]
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. [31]
Unit cell | Potassium coordination | Nitrate coordination |
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Potassium nitrate is moderately soluble in water, but its solubility increases with temperature. The aqueous solution is almost neutral, exhibiting pH 6.2 at 14 °C (57 °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. [2]
Between 550–790 °C (1,022–1,454 °F), potassium nitrate reaches a temperature-dependent equilibrium with potassium nitrite: [35]
Potassium nitrate has a wide variety of uses, largely as a source of nitrate.
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.
The most famous use of potassium nitrate is probably as the oxidizer in 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 motors, 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 bombs. [36] It is also added to cigarettes to maintain an even burn of the tobacco [37] and is used to ensure complete combustion of paper cartridges for cap and ball revolvers. [38] 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.
Potassium nitrate has been a common ingredient of salted meat since antiquity [39] or the Middle Ages. [40] The widespread adoption of nitrate use is more recent and is linked to the development of large-scale meat processing. [6] 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). [41] In the Shetland Islands (UK) it is used in the curing of mutton to make reestit mutton, a local delicacy. [42] When used as a food additive in the European Union, [43] the compound is referred to as E252; it is also approved for use as a food additive in the United States [44] and Australia and New Zealand [45] (where it is listed under its INS number 252). [2]
Since October 2015, WHO classifies processed meat as Group 1 carcinogen (based on epidemiological studies, convincingly carcinogenic to humans). [46]
In April 2023 the French Court of Appeals of Limoges confirmed that food-watch NGO Yuka was legally legitimate in describing Potassium Nitrate E249 to E252 as a "cancer risk", and thus rejected an appeal by the French charcuterie industry against the organisation. [47]
Potassium nitrate is used in fertilizers as a source of nitrogen and potassium – two of the macronutrients for plants. When used by itself, it has an NPK rating of 13-0-44. [48] [49]
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. [64] [65] 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 ] 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 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. [66]
In the Star Trek episode "Arena", Captain Kirk injures a gorn using a rudimentary cannon that he constructs using potassium nitrate as a key ingredient of gunpowder.[ citation needed ]
In 21 Jump Street , Jenko, played by Channing Tatum, gives a rhyming presentation about potassium nitrate for his chemistry class.[ citation needed ]
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 ]
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 ]
In the 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 cesspits.[ citation needed ]
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 ]
In the farming lore from the Corn Belt of the 1800s, drought-killed corn [67] 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". [68]
In the Slovenian short story 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 ]
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, charcoal, and potassium nitrate (saltpeter). The sulfur and charcoal act as fuels while the saltpeter is an oxidizer. Gunpowder has been widely used as a propellant in firearms, artillery, rocketry, and pyrotechnics, including use as a blasting agent for explosives in quarrying, mining, building pipelines, tunnels, and roads.
Nitrate is a polyatomic ion with the chemical formula NO−
3. 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 nitrate is bismuth oxynitrate.
Potassium hexacyanidoferrate(II) is the inorganic compound with formula K4[Fe(CN)6]·3H2O. It is the potassium salt of the coordination complex [Fe(CN)6]4−. This salt forms lemon-yellow monoclinic crystals.
Saltpeter (or saltpetre) is the mineral form of potassium nitrate (KNO3), a compound
Ammonium nitrate is a chemical compound with the formula NH4NO3. 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 predominantly used in agriculture as a high-nitrogen fertilizer.
Sodium nitrate is the chemical compound with the formula NaNO
3. This alkali metal nitrate salt is also known as Chile saltpeter to distinguish it from ordinary saltpeter, potassium nitrate. The mineral form is also known as nitratine, nitratite or soda niter.
The nitrite ion has the chemical formula NO−
2. Nitrite is widely used throughout chemical and pharmaceutical industries. The nitrite anion is a pervasive intermediate in the nitrogen cycle in nature. The name nitrite also refers to organic compounds having the –ONO group, which are esters of nitrous acid.
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 salt. It is a precursor to a variety of organic compounds, such as pharmaceuticals, dyes, and pesticides, but it is probably best known as a food additive used in processed meats and in fish products.
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.
Potassium nitrite (distinct from potassium nitrate) is the inorganic compound with the chemical formula KNO2. It is an ionic salt of potassium ions K+ and nitrite ions NO2−, which forms a white or slightly yellow, hygroscopic crystalline powder that is soluble in water.
The origins of meat preservation are lost to the ages but probably began when humans began to realize the preservative value of salt. Sausage making originally developed as a means to preserve and transport meat. Primitive societies learned that dried berries and spices could be added to dried meat. The procedure of stuffing meat into casings remains basically the same today, but sausage recipes have been greatly refined and sausage making has become a highly respected culinary art.
Charcuterie is a branch of French cuisine devoted to prepared meat products, such as bacon, ham, sausage, terrines, galantines, ballotines, pâtés, and confit, primarily from pork.
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 crystallizes in the trigonal system, but rarely occurs as well-formed crystals. It is isostructural with calcite. It is relatively soft and light with a Mohs hardness of 1.5 to 2 and a specific gravity of 2.24 to 2.29. Its refractive indices are nω = 1.587 and nε = 1.336.
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 generally a mixture of sodium chloride and sodium nitrite, and are used for pickling meats as part of the process to make sausage or cured meat such as ham, bacon, pastrami, corned beef, etc. Though it has been suggested that the reason for using nitrite-containing curing salt is to prevent botulism, a 2018 study by the British Meat Producers Association determined that legally permitted levels of nitrite have no effect on the growth of the Clostridium botulinum bacteria that causes botulism, in line with the UK's Advisory Committee on the Microbiological Safety of Food opinion that nitrites are not required to prevent C. botulinum growth and extend shelf life..
Curing is any of various food preservation and flavoring processes of foods such as meat, fish and vegetables, by the addition of salt, with the aim of drawing moisture out of the food by the process of osmosis. Because curing increases the solute concentration in the food and hence decreases its water potential, the food becomes inhospitable for the microbe growth that causes food spoilage. Curing can be traced back to antiquity, and was the primary method of preserving meat and fish until the late 19th century. Dehydration was the earliest form of food curing. Many curing processes also involve smoking, spicing, cooking, or the addition of combinations of sugar, nitrate, and nitrite.
Potassium nitrate is an oxidizer so storing it near fire hazards or reducing agents should be avoided to minimise risk in case of a fire.
Cured fish is fish which has been cured by subjecting it to fermentation, pickling, smoking, or some combination of these before it is eaten. These food preservation processes can include adding salt, nitrates, nitrite or sugar, can involve smoking and flavoring the fish, and may include cooking it. The earliest form of curing fish was dehydration. Other methods, such as smoking fish or salt-curing also go back for thousands of years. The term "cure" is derived from the Latin curare, meaning to take care of. It was first recorded in reference to fish in 1743.
Calcium nitrite is an inorganic compound with the chemical formula Ca(NO
2)
2. In this compound, as in all nitrites, nitrogen is in a +3 oxidation state. It has many applications such as antifreeze, rust inhibitor of steel and wash heavy oil.
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 and offered advice, instruction and guidance in the production of these materials. The Nitre and Mining Bureau was also known as the "CSNMB", the "Bureau of Nitre" or the "Nitre Bureau". The Niter and Mining Corps was the military division of the Bureau. The Nitre and Mining Bureau was part of the Confederate Ordnance Department, under the supervision of General Josiah Gorgas. The Nitre and Mining Bureau was supervised by General Isaac M. St. John. The Central Ordinance Laboratory was headed by John Mallet.
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."
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.
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.[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.]
Potassium nitrate 60mg