Potassium nitrate

Potassium nitrate ;
Names:	potassium nitrate; saltpetre; saltpeter; chinese salt; Е252 food additive;
Formula:	KNO3;
Molar mass:	101.102 g/mol;
Density:	2.109 g/cm3;
Crystal system:	orthorhombic (α); a=5.414 Å, b=9.166 Å, c=6.431 Åα=90°, β=90°, γ=90°; hexagonal (γ); a=5.487 Å, b=5.487 Å, c=9.156 Åα=90°, β=90°, γ=120°; hexagonal (β); a=5.425 Å, b=5.425 Å, c=9.836 Åα=90°, β=90°, γ=120°;
Shapes:	https://en.crystalls.info/w/uploads/media/6/6b/Prolongated_hexagonal_prism.json Prolongated hexagonal prism https://en.crystalls.info/w/uploads/media/3/36/Oblique_rhombic_prism.json Oblique rhombic prism https://en.crystalls.info/w/uploads/media/f/fd/Beveled_truncated_rhombic_prism.json Beveled truncated rhombic prism https://en.crystalls.info/w/uploads/media/1/12/Trapezoidal_flat_prism.json Trapezoidal flat prism https://en.crystalls.info/w/uploads/media/5/52/Needle.json Needle ;
Color:	colorless; white;
Melting point:	334 °C607.15 K <br />633.2 °F <br />1,092.87 °R <br /> (β);
Decomposition point:	100 °C373.15 K <br />212 °F <br />671.67 °R <br /> (α); 128 °C401.15 K <br />262.4 °F <br />722.07 °R <br /> (γ); 400 °C673.15 K <br />752 °F <br />1,211.67 °R <br /> (anhydrous);
Refractive index:	1.467 ;
Magnetic properties:	diamagnetic; χ=-3.37 · 10-5cm³/mol;
Stability:	slightly hygroscopic;
Hardness:	fragile;
Toxicity:	non-toxic; LD50=3750mg/kg

Description

Inorganic compound, salt of alkaline metal potassium and inorganic nitric acid. Doesn't form water hydrates.

Where to buy

Can be bought in fertilizers store (as "Potassium nitrate").

Precursors

Reaction between potassium hydroxide or carbonate and nitric acid

Chemical equation:

KOH + HNO₃ = KNO₃ + H₂O

K₂CO₃ + 2HNO₃ = 2KNO₃ + 2H₂O + CO₂↑

For preparation of 100.00g of potassium nitrate а 55.49g of potassium hydroxide or 68.35g of carbonate and 95.88g of 65%65% acid is required.

Add acid to the flask, then add small parts of potassium compound with stirring until it will totally dissolve or, if you use carbonate, until carbon dioxide emission will stop. After reaction will stop, filter the solution and use it for crystal growing.

Reaction between excess of potassium hydroxide or carbonate and ammonium nitrate

Chemical equation:

NH₄NO₃ + KOH = KNO₃ + H₂O + NH₃↑

2NH₄NO₃ + K₂CO₃ = 2KNO₃ + 2H₂O + 2NH₃↑ + CO₂↑

For preparation of 100.00g of potassium nitrate а 55.49g of potassium hydroxide or 68.35g of carbonate and 79.17g of ammonium nitrate is required.

Add to the flask saturated solution of potassium compound and then add small parts of hot ammonium nitrate solution with heating and stirring. Emission of large amount of ammonia will begin.Attention, exuding ammonia irritates eyes and lungs! The synthesis should be carried out only in a fume hood or outdoors!

Reaction between potassium chloride and ammonium nitrate

Chemical equation:

NH₄NO₃ + KCl = KNO₃↓ + NH₄Cl

For preparation of 100.00g of potassium nitrate а 73.74g of potassium chloride and 79.17g of ammonium nitrate is required.

Add to the flask with hot ammonium nitrate solution a potassium chloride solution with stirring. Cooling this mixture will cause forming a large amount of crystalline precipitate. Filter precipitate and wash it wish small amount of cold water, then filter the solution and use it for crystal growing.

Reaction between potassium chloride or carbonate and sodium nitrate

Chemical equation:

NaNO₃ + KCl = KNO₃ + NaCl↓

NaNO₃ + K₂CO₃ = 2KNO₃ + Na₂CO₃↓

For preparation of 100.00g of potassium nitrate а 68.35g of potassium carbonate or 73.74g of chloride and 84.07g of sodium nitrate is required.

Add to the flask with hot sodium nitrate solution a potassium compound solution with stirring. Cooling this mixture will cause forming a large amount of crystalline precipitate. After reaction will stop, filter the solution and use it for crystal growing.

Reaction between calcium or lead(II) nitrate and potassium hydroxide, carbonate or sulfate

You can use potassium chloride instead of sulfate in reaction with lead salt..
Chemical equation:

Ca(NO₃)₂ + 2KOH = Ca(OH)₂↓ + 2KNO₃

Pb(NO₃)₂ + 2KOH = Pb(OH)₂↓ + 2KNO₃

Ca(NO₃)₂ + K₂CO₃ = CaCO₃↓ + 2KNO₃

Pb(NO₃)₂ + K₂CO₃ = PbCO₃↓ + 2KNO₃

Ca(NO₃)₂ + K₂SO₄ = CaSO₄↓ + 2KNO₃

Pb(NO₃)₂ + K₂SO₄ = PbSO₄↓ + 2KNO₃

Pb(NO₃)₂ + 2KCl = PbCl₂↓ + 2KNO₃

For preparation of 100.00g of potassium nitrate а 55.49g of potassium hydroxide or 68.35g of carbonate or 86.18g of sulfate or 73.74g of chloride and 163.80g of lead(II) nitrate or 116.79g of calcium nitrate

tetrahydratetetrahydrate
anhydrous

is required.

Add to the flask with calcium or lead nitrate solution small parts of potassium salt solution and stir. The large amount of poorly soluble precipitate will form. Settle it out and discard, then filter the solution carefully.

Notes

Dissolving is endothermic, solution cools much, so use hot water or using heat.

Storage conditions

Keep in its original form or under several layers of varnish at average humidity and room temperature. Do not keep crystals near heaters.

Solubility

TableGraph

Temperature	g/`100,00` g water	g/`100,00` g ethanol 50%	g/`100,00` g ethanol	g/`100,00` g methanol	g/`100,00` g acetone	g/`100,00` g nitric acid	g/`100,00` g acetic acid	g/`100,00` g ammonia	g/`100,00` g hydrazine	g/`100,00` g dimethylformamide	g/`100,00` g ethylenediamine
0°C273.15 K <br />32 °F <br />491.67 °R <br />	`13.3`							`10.52`
10°C283.15 K <br />50 °F <br />509.67 °R <br />	`21.2`
15°C288.15 K <br />59 °F <br />518.67 °R <br />					`0.01`	`48.4`
20°C293.15 K <br />68 °F <br />527.67 °R <br />	`31.6`	`3.7`	`0.3`			`59.2`			`14`
25°C298.15 K <br />77 °F <br />536.67 °R <br />	`37.9`			`0.34`			`0.1765`	`10.4`		`1.5`	`0.37`
30°C303.15 K <br />86 °F <br />545.67 °R <br />	`46`
40°C313.15 K <br />104 °F <br />563.67 °R <br />	`61.3`
50°C323.15 K <br />122 °F <br />581.67 °R <br />						`107`
60°C333.15 K <br />140 °F <br />599.67 °R <br />	`106.2`
80°C353.15 K <br />176 °F <br />635.67 °R <br />	`166.6`
90°C363.15 K <br />194 °F <br />653.67 °R <br />	`199.5`
100°C373.15 K <br />212 °F <br />671.67 °R <br />	`245`

Soluble in glycerol and ethylene glycol. Slightly soluble in methylamine. Insoluble in diethyl ether.

Gallery

Slow cooling of saturated solutionPotassium nitrate, Laurentiu Alimpie, Flickr albumLaurentiu AlimpieFlickr album
Slow cooling of saturated solutionPotassium nitrate, Laurentiu Alimpie, Flickr albumLaurentiu AlimpieFlickr album
Slow cooling of saturated solutionPotassium nitrate, Laurentiu Alimpie, Flickr albumLaurentiu AlimpieFlickr album
Slow cooling of saturated solutionPotassium nitrate, Laurentiu Alimpie, Flickr albumLaurentiu AlimpieFlickr album
Rapid cooling of saturated solutionPotassium nitrate, Oscillator, Sciencemadness forumOscillatorSciencemadness forum

Video

Sources

Nitrates
Salts	Ammonium nitrate (NH₄NO₃) • Barium nitrate (Ba(NO₃)₂) • Bismuth(III) nitrate (BI(NO₃)₃) • Calcium nitrate (Ca(NO₃)₂) • Cesium nitrate (CsNO₃) • Cobalt(II) nitrate (Co(NO₃)₂) • Copper(II) nitrate (Cu(NO₃)₂) • Iron(II) nitrate (Fe(NO₃)₂) • Lead(II) nitrate (Pb(NO₃)₂) • Neodymium nitrate (Nd(NO₃)₃) • Nickel nitrate (Ni(NO₃)₂) • Potassium nitrate (KNO₃) • Silver(I) nitrate (AgNO₃) • Sodium nitrate (NaNO₃) • Strontium nitrate (Sr(NO₃)₂) • Uranyl nitrate (UO₂(NO₃)₂) • Zirconyl nitrate (ZrO(NO₃)₂)
Double salts	Calcium-ammonium nitrate (5Ca(NO₃)₂ · NH₄NO₃) • Cerium(IV)-ammomium nitrate (2NH₄NO₃ · Ce(NO₃)₄) • Cerium(III)-cobalt nitrate (3Co(NO₃)₂ · 2Ce(NO₃)₃) • Cerium(III)-cobalt-manganese nitrate (3(Co,Mn)(NO₃)₂ · 2Ce(NO₃)₃) • Cerium(III)-manganese nitrate (3Mn(NO₃)₂ · 2Ce(NO₃)₃)
Complexes	Bis-thetramethylethylenediaminecopper(II) nitrate ([Cu((H₃CNCH₃)₂C₄H₈)](NO₃)₂) • Nitratopentakis-karbamatbismuth(III) nitrate ([Bi(NO₃)(CO(NH₂)₂)₅](NO₃)₂) • Nitratopentakis-tiokarbamatbismuth(III) nitrate ([Bi(NO₃)(CS(NH₂)₂)₅](NO₃)₂)

Potassium compounds
Salts	Potassium bromate (KBrO₃) • Potassium bromide (KBr) • Potassium chlorate (KClO₃) • Potassium chloride (KCl) • Potassium chromate (K₂CrO₄) • Potassium dihydrophosphate (KH₂PO₄) • Potassium dichromate (K₂Cr₂O₇) • Potassium iodide (KI) • Potassium hydrofluoride (KHF₂) • Potassium hydrophosphate (K₂HPO₄) • Potassium hydrogen phthalate (KC₈H₆O₄) • Potassium metavanadate (KVO₃) • Potassium nitrate (KNO₃) • Potassium sulfate (K₂SO₄) • Potassium thiocyanate (KNCS)
Double salts	Aluminum-potassium sulfate (KAl(SO₄)₂) • Antimony(III)-potassium tartrate (K₂Sb₂(C₄H₂O₆)₂) • Chromium(III)-potassium sulfate (KCr(SO₄)₂) • Cobalt(II)-potassium sulfate (K₂Co(SO₄)₂) • Copper(II)-potassium sulfate (K₂Cu(SO₄)₂) • Indium(III)-potassium sulfate (KIn(SO₄)₂) • Iron(II)-potassium sulfate (K₂Fe(SO₄)₂) • Iron(III)-potassium sulfate (KFe(SO₄)₂) • Lithium-potassium sulfate (KLiSO₄) • Magnesium-potassium sulfate (K₂Mg(SO₄)₂) • Magnesium-potassium sulfate-chromate (K₂CrO₄ · MgSO₄) • Manganese(II)-potassium sulfate (K₂Mn(SO₄)₂) • Nickel-potassium sulfate (K₂Ni(SO₄)₂) • Potassium-sodium tartrate (KNaC₄H₄O₆) • Vanadium(III)-ammonium sulfate (NH₄V(SO₄)₂) • Zinc-potassium sulfate (K₂Zn(SO₄)₂)
Complexes	Potassium dioxalatocuprate(II) (K₂[Cu(C₂O₄)₂]) • Potassium hexanitrocobaltate(III) (K₃[Co(NO₂)₆]) • Potassium hexachlororhodiate(III) (K₃[RhCl₆]) • Potassium hexacyanocobaltate(III) (K₃[Co(CN)₆]) • Potassium hexacyanoferrate(II) (K₄[Fe(CN)₆]) • Tripotassium-sodium hexacyanoferrate(II) (K₃Na[Fe(CN)₆]) • Potassium hexacyanoferrate(III) (K₃[Fe(CN)₆]) • Potassium hexacyanochromate(III) (K₃[Co(CN)₆]) • Potassium tetraiodobismuthate (К[BiI₄]) • Potassium tetraiodomercurate(II) (K₂[HgI₄]) • Potassium trioxalatoaluminate (K₃[Al(C₂O₄)₃]) • Potassium trioxalatocobaltate(III) (K₃[Co(C₂O₄)₃]) Potassium trioxalatoferrate(III) (K₃[Fe(C₂O₄)₃]) • Potassium-sodium trioxalatoferrate(III) (K₅Na[Fe(C₂O₄)₃]₂) • Dipotassium-sodium trioxalatoferrate(III) (K₂Na[Fe(C₂O₄)₃]) • Potassium trioxalatochromate(III) (K₃[Cr(C₂O₄)₃])

Potassium nitrate
Names:	potassium nitrate saltpetre saltpeter chinese salt Е252 food additive
Formula:	KNO₃
Molar mass:	101.102 g/mol
Density:	2.109 g/cm³
Crystal system:	orthorhombic (α) a=5.414 Å, b=9.166 Å, c=6.431 Åα=90°, β=90°, γ=90° hexagonal (γ) a=5.487 Å, b=5.487 Å, c=9.156 Åα=90°, β=90°, γ=120° hexagonal (β) a=5.425 Å, b=5.425 Å, c=9.836 Åα=90°, β=90°, γ=120°
Shapes:	Prolongated hexagonal prism Oblique rhombic prism Beveled truncated rhombic prism Trapezoidal flat prism Needle
Color:	colorless white
Melting point:	334 °C607.15 K <br />633.2 °F <br />1,092.87 °R <br /> (β)
Decomposition point:	100 °C373.15 K <br />212 °F <br />671.67 °R <br /> (α) 128 °C401.15 K <br />262.4 °F <br />722.07 °R <br /> (γ) 400 °C673.15 K <br />752 °F <br />1,211.67 °R <br /> (anhydrous)
Refractive index:	1.467
Magnetic properties:	diamagnetic χ=-3.37 · 10^-5cm³/mol
Stability:	slightly hygroscopic
Hardness:	fragile
Toxicity:	non-toxic LD₅₀=3750mg/kg

Potassium nitrate

Description

Minerals

Where to buy

Precursors

Reaction between potassium hydroxide or carbonate and nitric acid

Reaction between excess of potassium hydroxide or carbonate and ammonium nitrate

Reaction between potassium chloride and ammonium nitrate

Reaction between potassium chloride or carbonate and sodium nitrate

Reaction between calcium or lead(II) nitrate and potassium hydroxide, carbonate or sulfate

Notes

Storage conditions

Solubility

Gallery

Video

Sources

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