Sodium Nitrite is an inorganic compound with chemical formula NaNO2 and as the sodium salt of nitrous acid HNO2. It forms white to slight yellowish crystalline powder in pure state. Sodium nitrate is hygroscopic and very soluble in water. It can be found in nature in several vegetables, such as spinach, parsley, lettuce, broccoli, curly kale, and asparagus. It also can be found in human body to control bacteria in the stomach and prevent gastroenteritis.
Sodium nitrite can be manufactured by reacting sodium hydroxide with nitrogen monoxide and nitrogen dioxide. The product from this process is sodium nitrite that diluted in water. To obtain crystalline sodium nitrite, it the solution undergoes to next stage which is evaporation. Sodium nitrite can be decomposed to sodium dioxide, nitrogen dioxide, and oxygen when it heated at high temperature. Also in laboratory scale, sodium nitrite can be used to destroy excess sodium azide.
The manufacturing process of sodium nitrite is by reacting sodium hydroxide with nitrogen dioxide and nitrogen monoxide. Product of this reaction is sodium nitrite and water. Sodium carbonate also can use as sodium hydroxide substitutes. The overall reaction of manufacturing sodium nitrite is shown below:
2NaOH + NO2 + NO → 2NaNO2 + H2O
The manufacturing process of sodium nitrite comprises the steps of:
(1) Absorption of nitrogen oxide in sodium hydroxide or sodium carbonate liquid
The nitrogen dioxide and nitrogen monoxide can be obtained from the manufacturing process of ammonia. It is preferable to use excess nitrogen oxide than nitrogen dioxide to increase the production of sodium nitrite and minimize the production of sodium nitrate. The absorption reaction of nitrogen dioxide and nitrogen monoxide in sodium hydroxide produce sodium nitrite solution.
Sodium nitrite solution that obtained then being cooled to crystallize. The product is suspensions that contain solid crystalline sodium nitrite in water. To increase the concentration, suspension is being heated until containing water evaporated. The evaporation process separates crystalline sodium nitrite from mother liquor.
Sodium nitrite is largely used as food stabilizer and additives since 1990s. As a food preservative, it prevents the growth of bacteria such as Clostridium botulinum that can cause botulism disease. Sodium nitrite also added color and taste to the non-vegetable food. Sodium nitrite can be found in fish and meat bacon, such as smoked fish, hot dogs, and luncheon meats. For safety, the use of sodium nitrite as food additive is limited to certain amount.
In pharmaceutical industry, sodium nitrite is used to treat several disease and organ damage. Sodium nitrite can prevent cell death in damage organ such as heart, lung, and liver. It also used as treatment for brain aneurysms, pulmonary hypertension, and Pseudomonas aeruginosa. Another used of sodium nitrite is to treat cyanides poisoning. But now it has been replaced by hydroxocobalamin.
Sodium nitrite is used as fertilizer and pesticides for several kind of plant. In fertilizer, sodium nitrite increases the amount of nitrogen that require for plant growth. It also strengthens the roots and prevents soil erosion. Insecticides, predacides, and rodenticides are examples of pesticides that used sodium nitrite. Sodium nitrite does not directly harm the pests and environmentally safe.
Other applications of sodium nitrite are manufacturing of nitroso compound, metal coatings for detinning and phosphating, corrosion inhibitor, photography, inhibitor of polymer, pulp and paper industries, lubricants, industrial and household cleaners, anti-freeze liquid, rubber processing, raw material for caffeine and saccharine production, water treatment, etc. Moreover, Sodium nitrite is often used as dyeing and bleaching agent in textile industry.