Как пишется калий нитрат

Нитрат калия
Общие
Систематическое наименование	Нитрат калия
Сокращения	в народе КС, НК
Традиционные названия	Ка́лиевая селитра, кали́йная селитра, индийская селитра, Соль Петра (Salt of Peter)[источник?]
Химическая формула	KNO3
Эмпирическая формула	KNO3
Физические свойства
Состояние (ст. усл.)	твёрдое
Отн. молек. масса	101,1032 а. е. м.
Молярная масса	101,1032 г/моль
Плотность	2,109 (16 °C) г/см³
Твёрдость	2
Термические свойства
Температура плавления	334 °C
Температура кипения	с разложением °C
Температура разложения	400 °C
Тройная точка	отсутствует
Молярная теплоёмкость (ст. усл.)	95,06 Дж/(моль·К)
Энтальпия образования (ст. усл.)	-494,00 кДж/моль
Энтальпия плавления	9,80 кДж/моль
Энтальпия сублимации	181,00 кДж/моль
Химические свойства
Растворимость в воде	13,3 (0 °C) 36 (25 °C) 247 (100 °C)
Классификация
Рег. номер CAS	7757-79-1
RTECS	TT3700000
Безопасность
ЛД50	3750 мг/кг
Токсичность	малотоксичен
NFPA 704	0 1 0 OX

Нитра́т ка́лия, азотноки́слый ка́лий (ка́лиевая сели́тра, кали́йная селитра, индийская селитра и др.) — неорганическое бинарное соединение, калиевая соль азотной кислоты с формулой KNO₃. В кристаллическом состоянии — бесцветное вещество, нелетучее, слегка гигроскопичное, без запаха. Нитрат калия хорошо растворим в воде. Практически не токсичен для живых организмов.

Встречается в природе в виде минерала нитрокалита, в Ост-Индии находятся одно из крупнейших месторождений, отсюда второе название — индийская селитра. В очень малых количествах содержится в растениях и животных^[1].

Форма кристаллов игольчатая, сами кристаллы очень длинные. Легко поддается очистке перекристаллизацией с минимальными потерями.

Основное применение находит в пиротехнике (до XX века особенно широко, как компонент основного в то время взрывчатого вещества — дымного (черного) пороха) и как калий-азотное удобрение (очень удобный комплекс двух обычно плохо сочетающихся при усваивании растениями элементов).

Физические свойства

Нитрат калия в нормальных условиях представляет собой бесцветные кристаллы (в измельченном состоянии белый порошок) с ионной структурой и ромбической или гексагональной кристаллической решеткой. Слегка гигроскопичен, склонен несильно слеживаться со временем. Не имеет запаха, нелетуч.

Хорошо растворим в воде, в средней степени в глицерине, жидком аммиаке, гидразине, нерастворим в чистом этаноле и эфире (в разбавленных водой растворяется плохо). Таблица растворимости в некоторых растворителях, в граммах KNO₃ на 100 г H₂O^[2][3]:

Растворитель / Температура	0 °С	10 °С	20 °С	25 °С	30 °С	40 °С	50 °С	60 °С	70 °С	80 °С	90 °С	100 °С
Вода	13,9	21,2	31,6	37,9	46,0	61,3		106,2		166,6		245,0
Жидкий аммиак	10,52			10,4
Гидразин			14
Диэтиловый эфир
Этанол
Метанол
Глицерин

При медленной кристаллизации вырастают очень длинные игольчатые кристаллы. Нитрат калия хорошо поддается очистке перекристаллизацией, причем с небольшими потерями, благодаря сильному повышению растворимости с ростом температуры.

Химические свойства

Разлагается при 400 °C с образованием нитрита калия KNO₂ и кислорода O₂ (выделение последнего увеличивает пожароопасность нитрата калия):

Является сильным окислителем, реагирует с горючими материалами и восстановителями, при измельчении активно и нередко со взрывом. В смеси с некоторыми органическими материалами склонен самовоспламенять их.

Расплав может быть использован для получения калия электролизом, однако из-за высоких окислительных способностей нитрата калия в этом состоянии предпочтительнее гидроксид калия.

Получение

В Средние Века и Новое Время (когда активно использовали порох) для получения нитрата калия служили селитря́ницы — кучи из смеси навоза (и других перегнивающих компонентов) с известняком, строительным мусором и прочим известняковым материалом с прослойками из соломы или хвороста, накрытые дерном для удерживания образующихся газов. При гниении навоза образовывался аммиак, который накапливаясь в прослойках из соломы, подвергался нитрификации и превращался вначале в азотистую, а затем в азотную кислоту. Последняя, взаимодействуя с известняком, давала Ca(NO₃)₂, который выщелачивался водой. Добавка древесной золы (состоящей в основном из поташа) приводила к осаждению CaCO₃ и получению раствора нитрата калия; нередко золу добавляли сразу в кучу вместо известняка, тогда калиевая селитра получалась сразу. Реакция поташа с кальциевой селитрой (нитратом кальция)

является самой древней из используемых человеком для получения нитрата калия и популярна до сих пор. Вместо поташа впрочем, сейчас в лабораториях чаще всего используют сульфат калия, реакция очень похожа:

Первый способ применялся до 1854 г., когда немецкий химик К. Нёльнер изобрел производство нитрата калия, основанное на реакции более доступных и дешевых хлорида калия и нитрата натрия:

Существует несколько других способов получения нитрата калия. Это взаимодействие нитрата аммония и хлорида калия с образованием нитрата калия и хлорида аммония, последний легко отделяется:

— популярнейшая после реакции нитрата кальция с карбонатом или сульфатом калия

— в основном демонстративная реакция соответствующей кислоты и основания

— тоже демонстративная реакция соответствующих кислоты и металла

— демонстр. реакция соотв. щелочного оксида с соотв. кислотой

Природные источники и месторождения

В природе калия нитрат распространен в виде минерала нитрокалита. Крупнейшие его месторождения находятся в Ост-Индии и в Чили (вместе с основным минералов — нитронатритом). Природный нитрат калия является результатом разложения азотистых веществ с последующим связыванием медленно выделяющегося аммиака нитробактериями, чему способствует влага и тепло, поэтому наиболее крупные залежи находятся в странах с жарким климатом^[4].

В очень малых количествах содержится в растениях и животных^[1], является промежуточным продуктом при переработке ими почвенных сульфата и карбоната калия.

Применение

Основное применение на сегодняшний день нитрат калия находит в качестве ценного удобрения, так как совмещает в себе два частично блокирующих усвоение друг друга растениями элемента.

Незаменим он при изготовлении дымного пороха и некоторых других составов (например, карамельного ракетного топлива), которые почти полностью сейчас идут на производство пиротехники.

Применяется также в электровакуумной промышленности и оптическом стекловарении для обесцвечивания и осветления технических хрустальных стекол и придания прочности изделиям из стекла^[5].

Расплав часто используется в лабораториях и у любителей для получения элементарного калия электролизом, наряду с гидроксидом калия.

Используется в качестве сильного окислителя в металлургии, в частности при переработке никелевых руд.

См. также

• Азотная кислота
• Нитраты
• Порох

Примечания

Ссылки

• Получение калиевой селитры

Растворимость кислот, оснований и солей в воде

H+ Li+ K+ Na+ NH4+ Ba2+ Ca2+ Mg2+ Sr2+ Al3+ Cr3+ Fe2+ Fe3+ Ni2+ Co2+ Mn2+ Zn2+ Ag+ Hg2+ Hg22+ Pb2+ Sn2+ Cu+ Cu2+ OH− P P P — P М Н М Н Н Н — Н Н Н Н Н — — Н Н Н Н F− P Н P P Р М Н Н М Р Н Н Н Р Р М Р Р М М Н Р Н Р Cl− P P P P Р Р Р Р Р Р Р Р Р Р Р Р Р Н Р Н М — Н Р Br− P P P P Р Р Р Р Р Р Р Р Р Р Р Р Р Н М Н М Р H Р I− P P P P Р Р Р Р Р Р  ? Р — Р Р Р Р Н Н Н Н М Н — S2− P P P P — Р М Н Р — — Н — Н Н Н Н Н Н Н Н Н Н Н SO32− P P P P Р М М М Н  ?  ? М  ? Н Н Н М Н Н Н Н  ? Н  ? SO42− P P P P Р Н М Р Н Р Р Р Р Р Р Р Р М — Н Н Р Р Р NO3− P P P P Р Р Р Р Р Р Р Р Р Р Р Р Р Р Р — Р — Р Р NO2− P P P P Р Р Р Р Р  ?  ?  ?  ? Р М  ?  ? М  ? ?  ?  ?  ?  ? PO43− P Н P P — Н Н Н Н Н Н Н Н Н Н Н Н Н Н  ? Н Н Н Н CO32− М Р P P Р Н Н Н Н — — Н — Н Н — Н Н — Н — —  ? — CH3COO− P Р P P Р Р Р Р Р — Р Р — Р Р Р Р Р Р М Р — Р Р CN− P Р P P Р Р Р Р Р ? Н Н — Н Н Н Н Н Р Н Р — — Н SiO32− H Н P P  ? Н Н Н Н ? ? Н ? ? ? Н Н ? ?  ? Н ? ? ?

Нитраты

Динитрат гидразина (N2H6(NO3)2) • Изопентилнитрат ((CH3)2CHCH2CH2ONO2) • Метилнитрат (CH3ONO2) • Нитрат актиния(III) (Ac(NO3)3) • Нитрат алюминия (Al(NO3)3) • Нитрат аммония (NH4NO3) • Нитрат бария (Ba(NO3)2) • Нитрат берилия (Be(NO3)2) • Нитрат висмута (Bi(NO3)3) • Нитрат гадолиния (Gd(NO3)3) • Нитрат гидразина (N2H5NO3) • Нитрат гидроксиламина ((NH3OH)NO3) • Нитрат гуанидина (C(NH2)3NO3) • Нитрат железа(III) (Fe(NO3)3) • Нитрат кадмия (Cd(NO3)2) • Нитрат калия (KNO3) • Нитрат кальция (Са(NО3)2) • Нитрат кобальта(II) (Co(NO3)2) • Нитрат кобальта(III) (Co(NO3)3) • Нитрат лития (LiNO3) • Нитрат магния (Mg(NO3)2) • Нитрат марганца (Mn(NO3)2) • Нитрат меди(II) (Cu(NO3)2) • Нитрат мочевины ((NH2)2CO•HNO3) • Нитрат натрия (NaNO3) • Нитрат неодима (Nd(NO3)3) • Нитрат никеля(II) (Ni(NO3)2) • Нитрат палладия(II) (Pd(NO3)3) • Нитрат ртути(I) (Hg2(NO3)2) • Нитрат ртути(II) (Hg(NO3)2) • Нитрат рубидия (RbNO3) • Нитрат свинца(II) (Pb(NO3)2) • Нитрат серебра(I) (AgNO3) • Нитрат скандия(III) (Sc(NO3)3) • Нитрат стронция (Sr(NO3)2) • Нитрат урана (U(NO3)2) • Нитрат уранила (UO2(NO3)2) • Нитрат хлорина (ClONO3) • Нитрат хрома (Cr(NO3)3) • Нитрат цезия (CsNO3) • Нитрат цинка (Zn(NO3)2) • Нитраты целлюлозы ([C6H7O2(OH)3-x(ONO2)x]n) • Нитроглицерин (O2NOCH(CH2ONO2)2) • Пропилнитрат (C3H7ONO2) • Церий-аммоний нитрат ((NH4)2Ce(NO3)6) • Этилнитрат (C2H5ONO2)

Соединения калия

Азид калия (KN3) • Амид калия (KNH2) • Ацесульфам (C4H4KNO4S) • Ацетат калия (CH3COOK) • Ацетиленид калия (K2C2) • Бензоат тригидрат калия (Брутто-формула:C7H11KO5) • Бромат калия (KBrO3) • Бромид калия (KBr) • Гексагидроксоплатинат(IV) калия (K2[Pt(OH)6]) • Гексагидроксостибат калия (K[Sb(OH)6]) • Гексанитрокобальтат(III) калия (K3[Co(NO3)6]) • Гексаоксибензол калия (C6(OK)6) • Гексафторогерманат калия (K2[GeF6]) • Гексафторокупрат(III) калия (K3CuF6) • Гексафторомолибдат(III) калия (K3MoF6) • Гексафтороплатинат(V) калия (K[PtF6]) • Гексафторосиликат(IV) калия (K2[SiF6]) • Гексафторфосфат калия (KPF6) • Гексахлоропалладат(IV) калия (K2[PdCl6]) • Гексахлороплатинат(IV) калия (K2[PtCl6]) • Гексахлоростаннат(IV) калия (K2[SnCl6]) • Гексахлорплатинат калия (K2PtCl6) • Гексацианоферрат(II) калия (K4[Fe(CN)6]) • Гексацианоферрат(II) тригидрат калия (K4[Fe(CN)6]•3H2O) • Гексацианоферрат(III) калия (K3[Fe(CN)6]) • Гептафторониобат(V) калия (K2[NbF7]) • Гидрид калия (KH) • Гидрокарбонат калия (KHCO3) • Гидроксид калия (KOH) • Гидроортофосфат калия (K2HPO4) • Гидросульфат калия (KHSO4) • Гидросульфид калия (KHS) • Гидросульфит калия (KHSO3) • Гидрофторид калия (KHF2) • Дигидроарсенат калия (KH2AsO4) • Дигидроортофосфат калия (KH2PO4) • Динитрамид калия (KN(NO2)2) • Дисульфат калия (K2S2O7) • Дисульфит калия (K2S2O5) • Дисульфонатнитроксил калия ((KO3S)2NO) • Дитионат калия (K2S2O6) • Дихлородиамминпалладий ([Pd(NH3)2]Cl2) • Дихромат калия (K2Cr2O7) • Дицианоаргентат(I) калия (K[Ag(СN)2]) • Дицианоаурат(I) калия (K[Au(СN)2]) • Иодат калия (KIO3) • Иодид калия (KI) • Карбонат калия (K2CO3) • Манганат калия (K2MnO4) • Метаванадат калия (KVO3) • Метасиликат калия (K2SiO3) • Метафосфат калия (KPO3) • Надпероксид калия (KO2 или K2O4) • Нитрат калия (KNO3) • Нитрит калия (KNO2) • Озонид калия (KO3) • Оксалат калия (K2C2O4) • Оксалат моногидрат калия (K2C2O4•H2O) • Оксид калия (K2O) • Октахлоромолибдат калия (K4Mo2Cl8) • Ортофосфат калия (K3PO4) • Пербромат калия (KBrO4) • Периодат калия (KIO4) • Перманганат калия (KMnO4) • Пероксид калия (K2O2) • Пероксодикарбонат калия (К2С2О6) • Пероксомоносульфат калия (K2SO5) • Пероксодисульфат калия (K2S2O6(O2)) • Перренат калия (KReO4) • Перхлорат калия (KClO4) • Полисульфиды калия (K2Sn) • Политионаты калия (K2SnO6) • Сегнетова соль (NaKC4H4O6) • Соль Джонсона (K[I(I)2]•H2O) • Соль Цейзе (K[Pt(C2H4)Cl3]•H2O) • Сорбат калия (C6H7KO2) • Сульфат гидрат калия-гадолиния • Сульфат гидрат калия-кальция (K2Ca(SO4)2•H2O) • Сульфат калия (K2SO4) • Сульфат калия-кальция (K2Ca(SO4)2) • Сульфат хрома(III)-калия (KCr(SO4)2) Сульфид калия (K2S) • Сульфит дигидрат калия (K2SO3•2H2O) • Сульфит калия (K2SO3) • Тетрагидроалюминат калия (KAlH4) • Тетрагидроксодиоксоосмат(VI) калия (K2[OsO2(OH)4]) • Тетрагидроортотеллурат калия (K2H4TeO6) • Тетраиодомеркурат(II) калия (K2[HgI4]) • Тетранитроплатинат(II) калия (K2[Pt(NO2)4]) • Тетраоксорутенат(VI) калия (K2RuO4) • Тетрапероксохромат(V) калия (K3CrO8) • Тетрасиликат калия (K2Si4O9•H2O) • Тетрахлоромолибдат(III) калия (KMoCl4) • Тетрахлоропалладат(II) калия (K2[PdCl4]) • Тетрахлороплатинат(II) калия (K2[PtCl4]) • Тетрахлороферрат(III) калия (K[FeCl4]) • Тетрахлорплатинат калия (K2PtCl4) • Тетрацианоникколат(II) калия (K2[Ni(CN)4]) • Тетрацианоплатинат(II) калия (K2[Pt(CN)4]) • Тиосульфат калия (K2SO3S) • Тиоцианат калия (KSCN) • Феррат калия (K2FeO4) • Феррооксалат калия (K3[Fe(C2O4)3]) • Формиат калия (HCOOK) Фталимид калия • Фторид калия (KF) • Фторсульфит калия (KSO2F) • Хлорат калия (KClO3) • Хлорид калия (KCl) • Хлорид-триэтилалюминий калия ((C2H5)3Al•KCl) • Хромат калия (K2CrO4) • Хромит калия (KCrO2) • Цианат калия (KOCN) • Цианид калия (KCN) • Цианоаурат калия (K[Au(CN)2] • Этилксантогенат калия (C2H5OC(S)SK) •

From Wikipedia, the free encyclopedia

Potassium nitrate^[1]

Names
IUPAC name Potassium nitrate
Other names Saltpeter Saltpetre Nitrate of potash Indian saltpeter Indian saltpetre[2]
Identifiers
CAS Number	7757-79-1
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL1644029
ChemSpider	22843
ECHA InfoCard	100.028.926
EC Number	231-818-8
E number	E252 (preservatives)
KEGG	D02051
PubChem CID	24434
RTECS number	TT3700000
UNII	RU45X2JN0Z
UN number	1486
CompTox Dashboard (EPA)	DTXSID4029692
InChI InChI=1S/K.NO3/c;2-1(3)4/q+1;-1  Key: FGIUAXJPYTZDNR-UHFFFAOYSA-N  InChI=1/K.NO3/c;2-1(3)4/q+1;-1 Key: FGIUAXJPYTZDNR-UHFFFAOYAM
SMILES [K+].[O-][N+]([O-])=O
Properties
Chemical formula	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)
Solubility in water	133 g/1000 g water (0 °C) 316 g/1000 g water (20 °C) 383 g/1000 g water (25 °C) 2439 g/1000 g water (100 °C)[3]
Solubility	slightly soluble in ethanol soluble in glycerol, ammonia
Basicity (pKb)	15.3[4]
Magnetic susceptibility (χ)	−33.7·10−6 cm3/mol
Refractive index (nD)	1.335, 1.5056, 1.5604
Structure
Crystal 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:
Pictograms
Hazard statements	H272, H315, H319, H335
Precautionary statements	P102, P210, P220, P221, P280
NFPA 704 (fire diamond)	1 0 0 OX
Flash point	non-flammable (oxidizer)
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1901 mg/kg (oral, rabbit) 3750 mg/kg (oral, rat)[5]
Safety data sheet (SDS)	ICSC 0184
Related compounds
Other anions	Potassium nitrite
Other cations	Lithium nitrate Sodium nitrate Rubidium nitrate Caesium nitrate
Related compounds	Potassium sulfate Potassium chloride
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).  verify (what is  ?) Infobox references

Potassium nitrate is a chemical compound with the chemical formula KNO
₃. This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K⁺ and nitrate ions NO₃⁻, and is therefore an alkali metal nitrate. It occurs in nature as a mineral, niter (or nitre in the UK).^[6] 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 saltpeter (or saltpetre in the UK).^[6]

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).^[7] In processed meats, potassium nitrate reacts with hemoglobin and myoglobin generating a red color.^[8]

Etymology[edit]

Potash, or potassium nitrate, because of its early and global use and production, has many names. The chemical potassium was first isolated by the chemist Sir Humphry Davy, from pot ash. This refers to an early method of extracting various potassium salts: by placing in an iron pot the ash of burnt wood or tree leaves, adding water, heating, and evaporating the solution.^[9]
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,^[10] 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» (Arabic: ثلج الصين thalj al-ṣīn). It was called «Chinese salt» by the Iranians/Persians^[11][12][13] or «salt from Chinese salt marshes» (Persian: نمک شوره چينی namak shūra chīnī).^{[14]: 335 [15]}

Historical production[edit]

From mineral sources[edit]

In Ancient India,^[when?] saltpeter manufacturers formed the Nuniya caste.^[16] Saltpeter finds mention in Kautilya’s Arthashastra (compiled 300BC — 300AD), which mentions using its poisonous smoke as a weapon of war,^[17] 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.^[18] 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.^[19]

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

From caves[edit]

Major natural sources of potassium nitrate were the deposits crystallizing from cave walls and the accumulations of bat guano in caves.^[20] 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.

Nitraries[edit]

Potassium nitrate was produced in a nitrary.^[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 come to the ground 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».^{[14]: 89, 311 [24]}

In 1561, Elizabeth I of England, 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 salpeter to growe» (the secret of the «Feuerwerkbuch» -the nitraries-).^[25]

Nitre bed[edit]

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.

French method[edit]

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.

Swiss method[edit]

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[edit]

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[edit]

Potassium nitrate can be made by combining ammonium nitrate and potassium hydroxide.

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,^[29] and potassium chloride, easily obtained as a sodium-free salt substitute.

NH₄NO₃ (aq) + KCl (aq) → NH₄Cl (aq) + KNO₃ (aq)

Potassium nitrate can also be produced by neutralizing nitric acid 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 and potassium chloride.

NaNO₃ (aq) + KCl (aq) → NaCl (aq) + KNO₃ (aq)

Properties[edit]

Potassium nitrate has an orthorhombic crystal structure at room temperature,^[30] 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).^[31][32]

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.^[33]

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.^[30]

Room temperature crystal structure and coordination geometry of potassium nitrate^[30]

Unit cell	Potassium coordination	Nitrate coordination

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.^[3]

Thermal decomposition[edit]

Between 550–790 °C (1,022–1,454 °F), potassium nitrate reaches a temperature-dependent equilibrium with potassium nitrite:^[34]

2 KNO₃ ⇌ 2 KNO₂ + O₂

Uses[edit]

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

Nitric acid production[edit]

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[edit]

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 fuel). It is also used in fireworks such as smoke bombs.^[35] It is also added to cigarettes to maintain an even burn of the tobacco^[36] and is used to ensure complete combustion of paper cartridges for cap and ball revolvers.^[37] 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[edit]

Potassium nitrate has been a common ingredient of salted meat since antiquity^[38] or the Middle Ages.^[39] The widespread adoption of nitrate use is more recent and is linked to the development of large-scale meat processing.^[7] The use of potassium nitrate has been mostly discontinued because of slow and inconsistent results compared to sodium nitrite compounds 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).^[40] When used as a food additive in the European Union,^[41] the compound is referred to as E252; it is also approved for use as a food additive in the United States^[42] and Australia and New Zealand^[43] (where it is listed under its INS number 252).^[3]

Food preparation[edit]

In West African cuisine, potassium nitrate (saltpetre) is widely used as a thickening agent in soups and stews such as okra soup^[44] and isi ewu. It is also used to soften food and reduce cooking time when boiling beans and tough meat. Saltpetre is also an essential ingredient in making special porridges, such as kunun kanwa^[45] literally translated from the Hausa language as «saltpetre porridge».

In the Shetland Islands (UK) it is used in the curing of mutton to make reestit mutton, a local delicacy.^[46]

Fertilizer[edit]

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.^[47][48]

Pharmacology[edit]

• Used in some toothpastes for sensitive teeth.^[49] Recently, the use of potassium nitrate in toothpastes for treating sensitive teeth has increased.^[50][51]
• Used historically to treat asthma.^[52] Used in some toothpastes to relieve asthma symptoms.^[53]
• Used in Thailand as main ingredient in kidney tablets to relieve the symptoms of cystitis, pyelitis and urethritis.^[54]
• Combats high blood pressure and was once used as a hypotensive.^[55]

Other uses[edit]

• Electrolyte in a salt bridge
• Active ingredient of condensed aerosol fire suppression systems. When burned with the free radicals of a fire’s flame, it produces potassium carbonate.^[56]
• 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.^[57]
• 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.^[58]
• To induce flowering of mango trees in the Philippines.^[59][60]
• 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 heliostats at the Gemasolar Thermosolar Plant. Ternary salts, with the addition of calcium nitrate or lithium nitrate, have been found to improve the heat storage capacity in the molten salts.^[61]
• 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.

In folklore and popular culture[edit]

Potassium nitrate was once thought to induce impotence, and is still rumored to be in institutional food (such as military fare) as an anaphrodisiac; however, there is no scientific evidence for such properties.^[62][63]

In Bank Shot, El (Joanna Cassidy) propositions Walter Ballantine (George C. Scott), 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 anaphrodisiac.

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.^[64]

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.

In 21 Jump Street, Jenko, played by Channing Tatum, gives a rhyming presentation about potassium nitrate for his chemistry class.

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.

In The Simpsons episode «El Viaje Misterioso de Nuestro Jomer (The Mysterious Voyage of Homer)», 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, 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 cesspits.

In the Dr Stone 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 of the 1800s, drought-killed corn^[65] 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».^[66]

See also[edit]

• History of gunpowder
• Humberstone and Santa Laura Saltpeter Works
• Niter, a mineral form of potassium nitrate
• Nitratine
• Nitrocellulose
• Potassium perchlorate

References[edit]

Bibliography[edit]

• Barnum, Dennis W. (December 2003). «Some History of Nitrates». Journal of Chemical Education. 80 (12): 1393. Bibcode:2003JChEd..80.1393B. doi:10.1021/ed080p1393.
• David Cressy. Saltpeter: The Mother of Gunpowder (Oxford University Press, 2013) 237 pp online review by Robert Tiegs
• Alan Williams. «The production of saltpeter in the Middle Ages», Ambix, 22 (1975), pp. 125–33. Maney Publishing, ISSN 0002-6980.

External links[edit]

• International Chemical Safety Card 018402216

From Wikipedia, the free encyclopedia

Potassium nitrate^[1]

Names
IUPAC name Potassium nitrate
Other names Saltpeter Saltpetre Nitrate of potash Indian saltpeter Indian saltpetre[2]
Identifiers
CAS Number	7757-79-1
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL1644029
ChemSpider	22843
ECHA InfoCard	100.028.926
EC Number	231-818-8
E number	E252 (preservatives)
KEGG	D02051
PubChem CID	24434
RTECS number	TT3700000
UNII	RU45X2JN0Z
UN number	1486
CompTox Dashboard (EPA)	DTXSID4029692
InChI InChI=1S/K.NO3/c;2-1(3)4/q+1;-1  Key: FGIUAXJPYTZDNR-UHFFFAOYSA-N  InChI=1/K.NO3/c;2-1(3)4/q+1;-1 Key: FGIUAXJPYTZDNR-UHFFFAOYAM
SMILES [K+].[O-][N+]([O-])=O
Properties
Chemical formula	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)
Solubility in water	133 g/1000 g water (0 °C) 316 g/1000 g water (20 °C) 383 g/1000 g water (25 °C) 2439 g/1000 g water (100 °C)[3]
Solubility	slightly soluble in ethanol soluble in glycerol, ammonia
Basicity (pKb)	15.3[4]
Magnetic susceptibility (χ)	−33.7·10−6 cm3/mol
Refractive index (nD)	1.335, 1.5056, 1.5604
Structure
Crystal 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:
Pictograms
Hazard statements	H272, H315, H319, H335
Precautionary statements	P102, P210, P220, P221, P280
NFPA 704 (fire diamond)	1 0 0 OX
Flash point	non-flammable (oxidizer)
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1901 mg/kg (oral, rabbit) 3750 mg/kg (oral, rat)[5]
Safety data sheet (SDS)	ICSC 0184
Related compounds
Other anions	Potassium nitrite
Other cations	Lithium nitrate Sodium nitrate Rubidium nitrate Caesium nitrate
Related compounds	Potassium sulfate Potassium chloride
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).  verify (what is  ?) Infobox references

Potassium nitrate is a chemical compound with the chemical formula KNO
₃. This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K⁺ and nitrate ions NO₃⁻, and is therefore an alkali metal nitrate. It occurs in nature as a mineral, niter (or nitre in the UK).^[6] 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 saltpeter (or saltpetre in the UK).^[6]

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).^[7] In processed meats, potassium nitrate reacts with hemoglobin and myoglobin generating a red color.^[8]

Etymology[edit]

Potash, or potassium nitrate, because of its early and global use and production, has many names. The chemical potassium was first isolated by the chemist Sir Humphry Davy, from pot ash. This refers to an early method of extracting various potassium salts: by placing in an iron pot the ash of burnt wood or tree leaves, adding water, heating, and evaporating the solution.^[9]
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,^[10] 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» (Arabic: ثلج الصين thalj al-ṣīn). It was called «Chinese salt» by the Iranians/Persians^[11][12][13] or «salt from Chinese salt marshes» (Persian: نمک شوره چينی namak shūra chīnī).^{[14]: 335 [15]}

Historical production[edit]

From mineral sources[edit]

In Ancient India,^[when?] saltpeter manufacturers formed the Nuniya caste.^[16] Saltpeter finds mention in Kautilya’s Arthashastra (compiled 300BC — 300AD), which mentions using its poisonous smoke as a weapon of war,^[17] 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.^[18] 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.^[19]

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

From caves[edit]

Major natural sources of potassium nitrate were the deposits crystallizing from cave walls and the accumulations of bat guano in caves.^[20] 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.

Nitraries[edit]

Potassium nitrate was produced in a nitrary.^[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 come to the ground 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».^{[14]: 89, 311 [24]}

In 1561, Elizabeth I of England, 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 salpeter to growe» (the secret of the «Feuerwerkbuch» -the nitraries-).^[25]

Nitre bed[edit]

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.

French method[edit]

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.

Swiss method[edit]

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[edit]

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[edit]

Potassium nitrate can be made by combining ammonium nitrate and potassium hydroxide.

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,^[29] and potassium chloride, easily obtained as a sodium-free salt substitute.

NH₄NO₃ (aq) + KCl (aq) → NH₄Cl (aq) + KNO₃ (aq)

Potassium nitrate can also be produced by neutralizing nitric acid 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 and potassium chloride.

NaNO₃ (aq) + KCl (aq) → NaCl (aq) + KNO₃ (aq)

Properties[edit]

Potassium nitrate has an orthorhombic crystal structure at room temperature,^[30] 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).^[31][32]

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.^[33]

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.^[30]

Room temperature crystal structure and coordination geometry of potassium nitrate^[30]

Unit cell	Potassium coordination	Nitrate coordination

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.^[3]

Thermal decomposition[edit]

Between 550–790 °C (1,022–1,454 °F), potassium nitrate reaches a temperature-dependent equilibrium with potassium nitrite:^[34]

2 KNO₃ ⇌ 2 KNO₂ + O₂

Uses[edit]

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

Nitric acid production[edit]

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[edit]

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 fuel). It is also used in fireworks such as smoke bombs.^[35] It is also added to cigarettes to maintain an even burn of the tobacco^[36] and is used to ensure complete combustion of paper cartridges for cap and ball revolvers.^[37] 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[edit]

Potassium nitrate has been a common ingredient of salted meat since antiquity^[38] or the Middle Ages.^[39] The widespread adoption of nitrate use is more recent and is linked to the development of large-scale meat processing.^[7] The use of potassium nitrate has been mostly discontinued because of slow and inconsistent results compared to sodium nitrite compounds 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).^[40] When used as a food additive in the European Union,^[41] the compound is referred to as E252; it is also approved for use as a food additive in the United States^[42] and Australia and New Zealand^[43] (where it is listed under its INS number 252).^[3]

Food preparation[edit]

In West African cuisine, potassium nitrate (saltpetre) is widely used as a thickening agent in soups and stews such as okra soup^[44] and isi ewu. It is also used to soften food and reduce cooking time when boiling beans and tough meat. Saltpetre is also an essential ingredient in making special porridges, such as kunun kanwa^[45] literally translated from the Hausa language as «saltpetre porridge».

In the Shetland Islands (UK) it is used in the curing of mutton to make reestit mutton, a local delicacy.^[46]

Fertilizer[edit]

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.^[47][48]

Pharmacology[edit]

• Used in some toothpastes for sensitive teeth.^[49] Recently, the use of potassium nitrate in toothpastes for treating sensitive teeth has increased.^[50][51]
• Used historically to treat asthma.^[52] Used in some toothpastes to relieve asthma symptoms.^[53]
• Used in Thailand as main ingredient in kidney tablets to relieve the symptoms of cystitis, pyelitis and urethritis.^[54]
• Combats high blood pressure and was once used as a hypotensive.^[55]

Other uses[edit]

• Electrolyte in a salt bridge
• Active ingredient of condensed aerosol fire suppression systems. When burned with the free radicals of a fire’s flame, it produces potassium carbonate.^[56]
• 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.^[57]
• 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.^[58]
• To induce flowering of mango trees in the Philippines.^[59][60]
• 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 heliostats at the Gemasolar Thermosolar Plant. Ternary salts, with the addition of calcium nitrate or lithium nitrate, have been found to improve the heat storage capacity in the molten salts.^[61]
• 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.

In folklore and popular culture[edit]

Potassium nitrate was once thought to induce impotence, and is still rumored to be in institutional food (such as military fare) as an anaphrodisiac; however, there is no scientific evidence for such properties.^[62][63]

In Bank Shot, El (Joanna Cassidy) propositions Walter Ballantine (George C. Scott), 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 anaphrodisiac.

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.^[64]

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.

In 21 Jump Street, Jenko, played by Channing Tatum, gives a rhyming presentation about potassium nitrate for his chemistry class.

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.

In The Simpsons episode «El Viaje Misterioso de Nuestro Jomer (The Mysterious Voyage of Homer)», 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, 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 cesspits.

In the Dr Stone 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 of the 1800s, drought-killed corn^[65] 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».^[66]

See also[edit]

• History of gunpowder
• Humberstone and Santa Laura Saltpeter Works
• Niter, a mineral form of potassium nitrate
• Nitratine
• Nitrocellulose
• Potassium perchlorate

References[edit]

Bibliography[edit]

• Barnum, Dennis W. (December 2003). «Some History of Nitrates». Journal of Chemical Education. 80 (12): 1393. Bibcode:2003JChEd..80.1393B. doi:10.1021/ed080p1393.
• David Cressy. Saltpeter: The Mother of Gunpowder (Oxford University Press, 2013) 237 pp online review by Robert Tiegs
• Alan Williams. «The production of saltpeter in the Middle Ages», Ambix, 22 (1975), pp. 125–33. Maney Publishing, ISSN 0002-6980.

External links[edit]

• International Chemical Safety Card 018402216

Нитрат калия, азотнокислый калий — неорганическое соединение, калиевая соль азотной кислоты с формулой KNO₃. В кристаллическом состоянии — бесцветное вещество, нелетучее, слегка гигроскопичное, без запаха. Нитрат калия хорошо растворим в воде. Практически не токсичен для живых организмов.

Нитрат калия
Общие
Систематическое наименование	Нитрат калия
Сокращения	в народе КС, НК
Традиционные названия	Ка́лиевая селитра, кали́йная селитра, индийская селитра, Соль Петра (Salt of Peter, petersalt)
Хим. формула	KNO3
Рац. формула	KNO3
Физические свойства
Состояние	твёрдое
Молярная масса	101,1032 г/моль
Плотность	2,109 (16 °C)
Твёрдость	2
Термические свойства
Температура
• плавления	334 °C
• кипения	с разложением °C
• разложения	400 °C
Тройная точка	отсутствует
Мол. теплоёмк.	95,06 Дж/(моль·К)
Энтальпия
• образования	-494,00 кДж/моль
• плавления	9,80 кДж/моль
• сублимации	181,00 кДж/моль
Химические свойства
Растворимость
• в воде	13,3 (0 °C) 36 (25 °C) 247 (100 °C)
Классификация
Рег. номер CAS	7757-79-1
PubChem	24434
Рег. номер EINECS	231-818-8
SMILES	[N+](=O)([O-])[O-].[K+]
InChI	1S/K.NO3/c;2-1(3)4/q+1;-1 FGIUAXJPYTZDNR-UHFFFAOYSA-N
Кодекс Алиментариус	E252
RTECS	TT3700000
ChEBI	63043
Номер ООН	1486
ChemSpider	22843
Безопасность
ЛД50	3750 мг/кг
Токсичность	малотоксичен
NFPA 704

Встречается в природе в виде минерала нитрокалита, в Ост-Индии находится одно из крупнейших месторождений, отсюда второе название — индийская селитра. В очень малых количествах содержится в растениях и животных.

Форма кристаллов игольчатая, сами кристаллы очень длинные. Легко поддаётся очистке перекристаллизацией с минимальными потерями.

Основное применение находит в пиротехнике (до XX века особенно широко, как компонент основного в то время взрывчатого вещества — дымного (чёрного) пороха) и как калий-азотное удобрение (очень удобное соединение двух обычно плохо сочетающихся при усваивании растениями элементов).

Физические свойства

Нитрат калия в нормальных условиях представляет собой бесцветные кристаллы (в измельчённом состоянии белый порошок) с ионной структурой и ромбической или гексагональной кристаллической решёткой. Слегка гигроскопичен, склонен несильно слеживаться со временем. Не имеет запаха, нелетуч.

Хорошо растворим в воде, в средней степени в глицерине, жидком аммиаке, гидразине, нерастворим в чистом этаноле и эфире (в разбавленных водой растворяется плохо). Таблица растворимости в некоторых растворителях, в граммах KNO₃ на 100 г H₂O:

Растворитель / Температура, °С	0	10	20	25	30	40	60	80	100
Вода	13,9	21,2	31,6	37,9	46,0	61,3	106,2	166,6	245,0
Жидкий аммиак	10,52			10,4
Гидразин			14

При медленной кристаллизации вырастают очень длинные игольчатые кристаллы. Нитрат калия хорошо поддаётся очистке перекристаллизацией, причём с небольшими потерями, благодаря сильному повышению растворимости с ростом температуры.

Химические свойства

• Разлагается при 400—520 °C с образованием нитрита калия KNO₂ и кислорода O₂ (выделение последнего увеличивает пожароопасность нитрата калия):

• Является сильным окислителем, реагирует с горючими материалами и восстановителями, при измельчении активно и нередко со взрывом. Смеси нитрата калия с некоторыми органическими материалами склонны к самовоспламенению.

• Восстанавливается водородом в момент выделения (в реакции соляная кислота разбавленная):

Реакция поташа с кальциевой селитрой (нитратом кальция) является самой древней из используемых человеком для получения нитрата калия и популярна до сих пор. Вместо поташа, впрочем, сейчас в лабораториях чаще всего используют сульфат калия, реакция очень похожа:

Существует несколько других способов получения нитрата калия. Это взаимодействие нитрата аммония и хлорида калия с образованием нитрата калия и хлорида аммония, последний легко отделяется:

— наиболее применимая после реакции нитрата кальция с карбонатом или сульфатом калия.

 — в основном, демонстрационная реакция соответствующей кислоты и основания

 — тоже демонстрационная реакция соответствующих кислоты и металла.

 — демонстрационная реакция соответствующего щелочного оксида с соответствующей кислотой.

Также:

Природные источники и месторождения

В природе нитрат калия распространён в виде минерала нитрокалита. Природный нитрат калия образуется в результате разложения азотсодержащих веществ с последующим связыванием медленно выделяющегося аммиака нитробактериями, чему способствует влага и тепло, поэтому наиболее крупные залежи находятся в странах с жарким климатом. Наиболее известные месторождения нитрата калия находятся в Индии, Боливии, Австралии, Чили, ЮАР, России, США и Шри-Ланке. Он также встречается в Китае, Мексике, и других странах

В очень малых количествах нитрат калия содержится в растениях и животных, является промежуточным продуктом при переработке ими почвенных сульфата и карбоната калия.

Применение

Основное применение на сегодняшний день нитрат калия находит в качестве ценного удобрения, так как совмещает в себе два элемента, частично блокирующих усвоение друг друга растениями, когда находятся в составе отдельных соединений.

Применяется при изготовлении дымного пороха и некоторых других горючих смесей (например, карамельного ракетного топлива), которые почти полностью сейчас используются в производстве пиротехнических изделий.

Применяется также в электровакуумной промышленности и оптическом стекловарении для обесцвечивания и осветления технических хрустальных стёкол и придания прочности изделиям из стекла.

Расплав иногда используется в химических лабораториях и у любителей химии для получения металлического калия электролизом, наряду с гидроксидом калия.

Используется в качестве сильного окислителя в металлургии, в частности, при переработке никелевых руд.

В пищевой промышленности нитрат калия применяется в качестве консерванта E252. Сам по себе он не имеет существенного антибактериального действия, но его оказывает образующийся в результате восстановления нитрит калия в мясных продуктах, в которых нитрат калия наиболее широко используется в качестве консерванта.