Sodium nitrite has a long and somewhat complicated history. It was first developed in the 1960s, and in 1977 the USDA considered banning it, but in 1984 its use as a food additive was allowed. Studies in the 1990s indicated that there could be adverse effects linked to the use of sodium nitrite as a food additive, and the National Toxicity Program (NTP) recommended listing the compound as a developmental and reproductive toxicant. However, in a report by the NTP in 2000, sodium nitrite was found to not be a toxic substance when used at approved levels and was removed from the list of developmental and reproductive toxicants.
Today, it is believed that sodium nitrite could prevent heart attacks and sickle cell disease and help with organ transplants and vascular problems in the legs. It is used in many products and industrial processes, including heat transfer salts, metal treatment and finishing, meat and fish preservatives, pharmaceuticals, and as an antidote to cyanide poisoning.
The Chemistry of Sodium Nitrite
Sodium nitrite is an inorganic salt with the chemical formula NaNO2. It can be in the form of a yellowish-white crystalline granule, powder, or rod. It is odorless and noncombustible but can assist in the burning of other combustible materials. As an ionic compound, it can be used as a strong reducing agent. When dissolved in an acid solution, it becomes a strong oxidizer.
Sodium nitrite can be synthesized through several different chemical reactions that involve the reduction of sodium nitrite. However, the industrial production of sodium nitrite is mainly achieved through the absorption of nitrogen oxides into an aqueous solution of sodium carbonate or sodium hydroxide.
Uses of Sodium Nitrite
Nitrite salts are a key ingredient in many industrial processes, and sodium nitrite is the most important of them. It is a precursor to several organic compounds used in pesticides, dyes, and pharmaceuticals. The compound is best known for its use as an additive in processed meats and fish, but it is also a major compound used in metallurgy and pharmaceuticals.
Major Industrial Applications of Sodium Nitrite
A major use of sodium nitrite is in the industrial production of organonitrogen compounds commonly used in pesticides. It is also used as a reagent in the conversion of amines into diazo compounds and other organic compounds that are used in the production of dyes, pigments, and printing ink. Sodium nitrite is also used in the synthesis of nitrites used to produce nitroso compounds that are used in the rubber and plastic industries as a blowing agent.
Sodium nitrite is used as a heat transfer medium and for phosphatizing and detinning in the production of steel and aluminum alloys. It is an anodic inhibitor that effectively interferes with the metal dissolution process. As the sodium nitrite reacts with dissolved oxygen, it forms a protective gamma iron oxide film on metal surfaces and reduces the rate of corrosion.
When mixed with nitrite salts, sodium nitrite can be used to create a molten salt bath that is stable at high temperatures, has a low melting point and high heat transfer rate, and is non-corrosive to steel. These molten salt baths are used for indirect heating and cooling or as a quenching bath in the process of annealing iron and steel.
As a result, sodium nitrite offers excellent protection for ferrous metals, such as those used in closed-loop water systems. Since sodium nitrite functions best at a pH range of 9.0-10.5, it is often formulated with borate buffers in closed-loop systems. When combined with sodium nitrite, borates help to facilitate the absorption of oxygen and provide microbiological control. Sodium nitrite is commonly used as an aqueous solution in closed-loop heating and cooling systems.
Thanks to its corrosion-inhibiting properties, it is also used as an additive in industrial greases used in medium-speed, moderate-temperature applications on chassis, gears, wheel bearings, ball bearings, conveyors, machine parts, and other moving parts.
Sodium nitrite is used many other industrial processes, such as an acid neutralizer after chromium tanning in leather manufacturing and as a raw material for baking powder as a food additive. It is used in synthesizing, processing, and purifying chemicals and polymers and serves as a catalyst, neutralizing, and buffering agent.
Sodium nitrite is a safe and effective chemical used for the biological control of wastewater treatment. It helps maintain proper pH levels in wastewater, control sulfide odors, and reduces the demand for biological oxygen. The compound is also proven to be one of the most effective collectors of sulfur dioxide. Due to its odor-absorbing properties, and is used in deodorizers for carpets, refrigerators, and garbage containers. It is even used in the agricultural industry as a buffer to maintain the pH levels of rumens and alleviate butterfat depressions due to diets low in fiber and to aid in fiber digestibility. In the poultry industry, sodium nitrite is used to maintain electrolyte balance, improve tolerance to heat stress, and improve eggshell quality.
How Sodium Nitrite is Used in Meat Curing and Preserving
The most common use of sodium nitrite in the food industry is as an additive that speeds up the curing process of meats and fish. When sodium nitrite is added to meat, it reacts with myoglobin and causes color changes. At first, the myoglobin is converted to nitrosomyoglobin, which results in a bright red color. Then when heated, the nitrosomyoglobin is converted to nitrosohemochrome, resulting in a pink color. When used for curing, sodium nitrite is always mixed with salt in what is commonly referred to as pink salt. This mixture typically only contains 0.5% to 0.9% sodium nitrite.
Sodium nitrite is effective at delaying the development of lipid peroxidation, which is the major cause of oxidative rancidity. It acts as an antioxidant and reacts with heme proteins and metal ions to neutralize free radicals produced by nitric oxide. Neutralizing these free radicals terminates the cycle of lipid oxidation and thereby extends the shelf life of cured meats while maintaining visual appeal and taste.
Pharmaceutical Applications of Sodium Nitrite
The use of sodium nitrite in the pharmaceutical industry started in the 1920s and 1930s, and it is listed on the World Health Organization’s List of Essential Medications. Its most common use in the pharmaceutical industry is in the treatment of cyanide poisoning. It is mixed with sodium thiosulfate and used as an injection. Sodium nitrite has also proven to be an effective treatment for hydrogen sulfide poisoning. It is also used as a raw ingredient in the synthesis of saccharines and caffeine.
Research has shown sodium nitrite to be an effective vasodilator that could be used to treat many conditions, such as stroke, heart attack, sickle cell anemia, respiratory diseases, and fungal, bacterial, and viral infections. It has also been shown to be useful in reducing the risk of hospital-acquired nocosomial infections that result from the insertion of medical devices such as catheters.
Noah Chemicals will work with you to meet your sodium nitrite (NaNO2) needs. We supply multiple grades of sodium nitrite for multiple industries, including preservatives, pharmaceuticals, color fixatives, paints, heat transfer salts, and metal finishing. For more information or to request a quote, reach out to our team here.
Please note, Noah Chemicals is a B2B company and we do not sell any materials or chemicals to the general public nor to any residential locations. All customers must be verified as a business and vetted prior to purchasing materials.
