In inorganic chemistry, nitrites are salts of nitrous acid (HNO2). They contain the nitrite ion (NO2-). Nitrites of the alkali and alkaline earth metals can be synthesized by reacting a mixture of nitrogen monoxide (NO) and nitrogen dioxide (NO2) with a corresponding metal hydroxide solution, as well as through the thermal decomposition of the corresponding nitrate. Other nitrites are available through the reduction of the corresponding nitrates.
Ammonium nitrite, NH4NO2, is a salt which contains ammonium and nitrite ions. It is used as a rodenticide, microbiocide and agricultural pesticide, and is acutely toxic to both humans and aquatic organisms.
It can be formed by oxidizing ammonia with ozone or hydrogen peroxide, or in a precipitation reaction of barium or lead nitrite with ammonium sulfate, or silver nitrite with ammonium chloride. The precipitate is filtered off and the solution concentrated. It forms colorless crystals which are soluble in water and decompose on heating or in the presence of acid, with the formation of nitrogen. 
NH4NO2 -> N2 + 2H2O
Sodium nitrite, with chemical formula NaNO2, is used as a color fixative and preservative in meats and fish. When pure, it is a white to slight yellowish crystalline powder. It is very soluble in water and is hygroscopic. It is also slowly oxidized by oxygen in the air to sodium nitrate, NaNO3. The compound is a strong reducing agent.
It is also used in manufacturing diazo dyes, nitroso compounds, and other organic compounds; in dyeing and printing textile fabrics and bleaching fibers; in photography; as a laboratory reagent and a corrosion inhibitor; in metal coatings for phosphatizing and detinning; and in the manufacture of rubber chemicals. Sodium nitrite also has been used in human and veterinary medicine as a vasodilator, a bronchodilator, an intestinal relaxant or a laxative, and an antidote for cyanide poisoning.
Potassium nitrite, with chemical formula KNO2, is a material which contains Potassium and Nitrogen.
As a food additive, potassium nitrite is used as a preservative in a manner similar to that of sodium nitrite. It has the E number E249.
Potassium nitrite is a strong oxidizer and contact with skin or clothing, as well as inhalation and ingestion, should be avoided. Potassium nitrite is used in the manufacturing of heat transfer salts, and is highly combustable.
Colorless transparent liquid boiling point of 61-63, flash point of -10. Soluble in aether and ethanol etc. Not