What Is Potassium Nitrite?
Potassium nitrite is a compound with the molecular formula KNO2.
It is a white or pale yellow crystalline powder. It is deliquescent and soluble in water, and its aqueous solution is alkaline. It is known to be a strong oxidizing agent and a flame retardant. It can be explosive when heated above 530°C, so it should be handled with care.
In terms of safety, it has been shown to be irritating to the eyes and skin.
Uses of Potassium Nitrite
Potassium nitrite is widely used mainly as a food preservative, in wastewater treatment, and in the production of metal oxide membranes for fuel cells.
1. Food Preservative
When potassium nitrite is used in food, it is effective in the form of nitrous acid. It is often used together with sodium nitrite as a coloring agent for ham, sausage, bacon, cod roe, salmon roe, etc. to prevent the growth of bacteria and to give meat a pink color.
It is also used as a fermentation regulator for cheese and sake.
2. Raw Material for the Manufacture of Pharmaceuticals
Potassium nitrite is used in the manufacture of nitroglycerin, a drug for angina pectoris, and sodium nitrite, a drug for cyanide poisoning.
Properties of Potassium Nitrite
Potassium nitrite (KNO2) is a white to slightly yellow crystalline powder. It is slightly hygroscopic, absorbing moisture in the air and gradually dissolving. Its melting point is 441°C and boiling point is about 600°C. It is well soluble in water, but insoluble in organic solvents such as ethanol, ether, and benzene.
It has a simple linear molecular structure consisting of a potassium cation (K+) and a nitrite anion (NO2-). Potassium nitrite is a strong oxidant and can react with a variety of organic and inorganic compounds. When potassium nitrite is heated to between 550°C and 790°C in the presence of oxygen, it undergoes thermal decomposition to form potassium nitrite.
At this time, it releases nitrogen gas, resulting in a significant increase in volume. Potassium nitrite also reacts very slowly with liquid ammonia solutions of potassium amide in the presence of ferric oxide or cobalt oxide at room temperature to form nitrogen and potassium hydroxide.
Besides, potassium nitrite can form explosive compounds when mixed with other substances, such as ammonium nitrite and organic compounds. Thus, potassium nitrite has a wide range of uses due to its physical and chemical properties. However, it can be dangerous if not handled properly.
Other Information on Potassium Nitrite
How Potassium Nitrite Is Produced
Potassium nitrite can be produced in several ways. A typical method is the reaction of potassium hydroxide (KOH) with nitrous acid (HNO2). Nitrous acid is synthesized in situ by reacting sodium nitrite (NaNO2) with hydrochloric acid (HCl). The reaction proceeds with the following equation:
2KOH + HNO2 → KNO2 + KNO3 + H2O
The resulting mixture can be separated by crystallization. Another method is to react potassium carbonate (K2CO3) with nitrite to produce potassium nitrite together with potassium nitrate, or to react potassium nitrate (KNO3) with metal iron to reduce nitrate to nitrite.
In both methods, potassium nitrite is a strong oxidizing agent and can be dangerous if not handled properly. Potassium nitrite is also soluble in water, making it difficult to recover solids.