Potassium nitrate

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  Potassium nitrate   
Names: potassium nitrate
saltpetre
saltpeter
chinese salt

Formula: KNO3
SMILES: [N+](=O)([O-])[O-].[K+]
Molar mass: 101.102 g/mol
Density: 2.109 g/cm3
Crystal system: orthorhombic (α)
a=5.414 Å
5.4140 Å
0.5414 nm
, b=9.166 Å
9.1660 Å
0.9166 nm
, c=6.431 Å
6.4310 Å
0.6431 nm
α=90°
90°  
, β=90°
90°  
, γ=90°
90°  

hexagonal (γ)
a=5.487 Å
5.4870 Å
0.5487 nm
, b=5.487 Å
5.4870 Å
0.5487 nm
, c=9.156 Å
9.1560 Å
0.9156 nm
α=90°
90°  
, β=90°
90°  
, γ=120°
120°  

hexagonal (β)
a=5.425 Å
5.4250 Å
0.5425 nm
, b=5.425 Å
5.4250 Å
0.5425 nm
, c=9.836 Å
9.8360 Å
0.9836 nm
α=90°
90°  
, β=90°
90°  
, γ=120°
120°  

Shapes:
https://media.crystalls.info/w/uploads/media/Prolongated_hexagonal_prism.json
https://media.crystalls.info/w/uploads/media/Oblique_rhombic_prism.json
https://media.crystalls.info/w/uploads/media/Beveled_truncated_rhombic_prism.json
https://media.crystalls.info/w/uploads/media/Trapezoidal_flat_prism.json
https://media.crystalls.info/w/uploads/media/Needle.json

Color: colorless
white
Melting point: 334 °C
607.15 K
633.2 °F
1,092.87 °R
(β)
Decomposition point: 100 °C
373.15 K
212 °F
671.67 °R
(α)
128 °C
401.15 K
262.4 °F
722.07 °R
(γ)
400 °C
673.15 K
752 °F
1,211.67 °R
(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.

Minerals

Occurs in nature as niter mineral.

Where to buy

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% 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 heating and stirring. Cooling this mixture will cause forming a large amount of crystalline precipitation. 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 heating and stirring. Cooling this mixture will cause forming a large amount of crystalline precipitation. 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 tetrahydrate 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

Store in its original form or under several layers of varnish at average humidity and room temperature. Do not store in matchboxes or cotton wool and do not heat.

Solubility

Temperatureгр/100,00 гр waterгр/100,00 гр ethanolгр/100,00 гр ethanol 50%гр/100,00 гр methanolгр/100,00 гр acetoneгр/100,00 гр nitric acidгр/100,00 гр acetic acidгр/100,00 гр ammoniaгр/100,00 гр hydrazineгр/100,00 гр ethylenediamineгр/100,00 гр dimethylformamideгр/100,00 гр trichlorethylene
0°C
273.15 K
32 °F
491.67 °R
13.3
13.3 g/100g
11.739 %
10.52
10.52 g/100g
9.519 %
10°C
283.15 K
50 °F
509.67 °R
21.2
21.2 g/100g
17.492 %
15°C
288.15 K
59 °F
518.67 °R
~26.4
26.4 g/100g
20.886 %
0.01
0.01 g/100g
0.01 %
48.4
48.4 g/100g
32.615 %
0.01
0.01 g/100g
0.01 %
20°C
293.15 K
68 °F
527.67 °R
31.6
31.6 g/100g
24.012 %
0.3
0.3 g/100g
0.299 %
3.7
3.7 g/100g
3.568 %
59.2
59.2 g/100g
37.186 %
14
14 g/100g
12.281 %
25°C
298.15 K
77 °F
536.67 °R
37.9
37.9 g/100g
27.484 %
0.34
0.34 g/100g
0.339 %
~67.2
67.2 g/100g
40.191 %
0.1765
0.177 g/100g
0.176 %
10.4
10.4 g/100g
9.42 %
0.37
0.37 g/100g
0.369 %
1.5
1.5 g/100g
1.478 %
30°C
303.15 K
86 °F
545.67 °R
46
46 g/100g
31.507 %
~75.2
75.2 g/100g
42.922 %
40°C
313.15 K
104 °F
563.67 °R
61.3
61.3 g/100g
38.004 %
~91.1
91.1 g/100g
47.671 %
50°C
323.15 K
122 °F
581.67 °R
~83.8
83.8 g/100g
45.593 %
107
107 g/100g
51.691 %
60°C
333.15 K
140 °F
599.67 °R
106.2
106.2 g/100g
51.503 %
70°C
343.15 K
158 °F
617.67 °R
~136
136 g/100g
57.627 %
80°C
353.15 K
176 °F
635.67 °R
166.6
166.6 g/100g
62.491 %
90°C
363.15 K
194 °F
653.67 °R
199.5
199.5 g/100g
66.611 %
100°C
373.15 K
212 °F
671.67 °R
245
245 g/100g
71.014 %
Soluble in glycerol and ethylene glycol. Slightly soluble in methylamine. Insoluble in diethyl ether.

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