Potassium nitrate

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Potassium nitrate
Chemical formula {{#Chem:KNO3}}
OTP appearance white crystal 
Molar Mass(g/mol) 101.1032 
Density(g/cc) 2.109 
Melting Point(°C) 334 
Solubility in water(g/L) 316 
Solubility in ethanol(g/L) non
NFPA 704
0
1
0
OX

 

Thermal Decomposition
Potassium nitrate
400°C
{{#Chem: KNO2, O2}}

Uses

Primary

Natural occurrence

  • Chilean saltpeter is a mixture of potassium nitrate and sodium nitrate
  • Baraud is another evaporite mineral which contains potassium nitrate

Hazards

  • Oxidizer

Production

Synthesis

From nitric acid

  • Combine nitric acid and aqueous potassium hydroxide. Keep cool in a water bath. Once reaction is complete, evaporate the water.
    {{#Chem: HNO3 + KOH = KNO3 + H2O}}

From calcium nitrate

Calcium nitrate is the most common nitrate from composting or ammonia biofiltration. Calcium easily forms insoluble salts, giving an easy metathesis reaction:

  • Combine calcium nitrate and potassium carbonate
    {{#Chem: Ca(NO3)2(aq) + K2CO3(aq) = CaCO3(s) + 2KNO3}}

From sodium nitrate

This leverages the steep solubility curve of potassium nitrate.

  1. Prepare saturated solutions of sodium nitrate and potassium chloride at 99°C
  2. Combine the solutions such that they are in a 1:1 molar ratio
  3. Cool the mixture to near freezing
  4. The precipitate is potassium nitrate
    {{#Chem: NaNO3(aq) + KCl(aq) --> NaCl + KNO3|t=1|p=atm}}

Properties

See Also

References