Potassium nitrite represented by the chemical formula KNO₂ is a yellowish white crystalline and deliquescent powder that is soluble in water, alcohol and liquid ammonia ^[1]. It is a potassium salt and an ionic compound ^{[1, 3]}. KNO₂ is a strong oxidizer and incompatible with strong acids, strong reducing agents, cyanides, ammonium salts and combustible materials ^[6].

Potassium Nitrite Identification
CAS Number	7758-09-0 [1]
PubChem CID	516910 [1]
ChemSpider ID	22857 [2]
EC Number	231-832-4 [1]

How to Make It

Potassium nitrite can be prepared by heating potassium nitrate with lead.

KNO₃ + Pb = KNO₂ + PbO

If you want, you can use zinc or copper instead of lead ^[5].

Properties and Characteristics of Potassium Nitrite

General Properties
Molar mass/molecular weight	85.103 g/mol [1]
Physical Properties
Color/appearance	White or slightly yellow crystals [1]
Melting point/freezing point	441°C, 825.8°F [1]
Boiling point	537°C, 998.6°F [1]
Density	1.9 g cm-3 [1]
State of matter at room temperature (normal phase)	Solid [1]
Heat capacity	107.4 J/mol K [1]
Specific gravity	1.915 [6]
Chemical Properties
Flammability	Yes [4]
Solubility in water	3120 g/l (at 25oC) [1]
pH	8.40 (basic) [3]

Prominent Reactions

A reaction between potassium nitrite and concentrated nitric acid produces potassium nitrate, nitrogen dioxide, nitric oxide and water ^[7].

2KNO₂ + 2HNO₃ = 2KNO₃ + NO₂ + NO + H₂O

A saturated solution of KNO₂ reacts with concentrated sulfuric acid to produce potassium sulfate, nitrogen dioxide, nitric oxide and water ^[8].

2KNO₂ + H₂SO₄ = K₂SO₄ + NO₂ + NO + H₂O

Potassium nitrite reacts with concentrated hydrochloric acid to form potassium nitrate, potassium chloride, nitric oxide and water ^[9].

3KNO₂ + 2HCl = KNO₃ + 2KCl + 2NO + H₂O

Potassium Nitrite Uses

1. To make other chemicals, heat transfer salts ^{[1, 6]}.
2. In chemical analysis ^[1].
3. As a food additive (preservative), in fertilizers ^[4].
4. As an antidote to cyanide poisoning ^[4].
5. As a vasodilator in the medical field ^[4].
6. As an anti-scaling agent and corrosion inhibitor ^[6].

Is It Dangerous

It is a poison if ingested. It may cause explosion hazard if heated. The compound begins decomposing at 350°C and emits toxic fumes of potassium oxide. KNO₂ in food can increase the risk of cancer ^{[1, 4]}.

Potassium Nitrite Price

10 gram of the compound costs around $19.2 ^[6].

References
1. Potassium Nitrite – Pubchem.ncbi.nlm.nih.gov
2. Potassium Nitrite – Chemspider.com
3. What is the pH of a 0.25M solution of potassium nitrite? – Quora.com
4. Potassium Nitrite – Chemicalbook.com
5. Preparation of potassium nitrite – Prepchem.com
6. Potassium Nitrite – Chemicalbook.com
7. Potassium nitrite react with nitric acid – Chemiday.com
8. Potassium nitrite react with sulfuric acid – Chemiday.com
9. Potassium nitrite react with hydrogen chloride – Chemiday.com