Sodium nitrite is an inorganic compound with the chemical formula NaNO₂. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic. From an industrial perspective, it is the most important nitrite salt. Technically, NaNO₂ has a molar mass of about 69.00 g mol^-1 and is commonly supplied as anhydrous or low moisture granular material; it forms nitrous acid under acidic conditions and can act as an oxidizing agent in some reactions and as a nitrosating reagent in synthetic chemistry. It is chemically stable under normal storage but decomposes on strong heating to give nitrogen oxides and sodium oxides, and it is incompatible with strong reducing agents, acids, and ammonium salts. Typical industrial handling notes include storage in a cool, dry, well ventilated area, protection from contamination with combustible materials, and segregation from acids and reducing substances.
Commercial grades of sodium nitrite vary by intended use and therefore impurity limits differ by specification. Typical technical grade material is commonly specified at about 95 to 98 percent NaNO₂, whereas food or reagent grades are usually 99 to 99.9 percent NaNO₂. Common impurities and typical control levels include sodium nitrate (NaNO₃) often below 0.5 to 2.0 percent depending on grade, chloride and sulfate salts generally below 0.1 to 0.5 percent, moisture content commonly specified between 0.1 and 2.0 percent, and insolubles usually under 0.02 percent for high purity grades. Trace metals such as iron, lead, and arsenic are controlled at ppm levels for refined grades; specific maximums depend on regulatory and customer requirements. Related compounds present in handling, processing, or byproduct streams include sodium nitrate, potassium nitrite, nitrous acid derivatives, and potential nitrosating species; formation of organic nitrosamines is a concern in some downstream applications and is managed by process controls and analytical monitoring.
Sodium nitrite is used across multiple industries as a corrosion inhibitor in closed loop systems and cooling circuits, as a curing agent and preservative in meat processing under tightly regulated limits, as an intermediate in the manufacture of dyes, pharmaceuticals, and agrochemicals, and as a reagent for analytical chemistry and organic synthesis where nitrosation or diazotization is required. It is also used in metal treatment and heat transfer formulations and in certain water treatment applications. Regulatory and quality specifications vary by use, so product grade and impurity limits are selected to meet the intended application.
Sodium nitrite is toxic at sufficient exposure levels and can cause methemoglobinemia if ingested, which reduces the bloods ability to carry oxygen. Acute oral toxicity and inhalation risks require controlled handling, use of appropriate personal protective equipment, and adherence to occupational exposure limits. In food applications it is used at regulated low concentrations and residues are monitored because of the potential for nitrosamine formation under certain conditions. Emergency procedures, proper storage away from acids and reducing agents, and compliance with safety data sheet guidance are essential to minimize health and safety risks.
