Sodium Nitrite

About This Product

Sodium nitrite has the formula NaNO2 and CAS number 7632-00-0, supplied as white to pale yellow crystals or granules, very soluble in water and hygroscopic. It is produced by absorbing nitrogen oxides in alkali, and is distinct from sodium nitrate in both chemistry and hazard. One fewer oxygen atom changes the behaviour entirely. Nitrate is stable and comparatively inert; nitrite is reactive, acting as both an oxidising and a reducing agent depending on conditions, and it is the reagent that converts aromatic amines to diazonium salts, the reaction on which the whole azo dye industry is built. In corrosion inhibition it works by passivation: nitrite oxidises the steel surface to form a thin, adherent, self-repairing oxide film that stops further attack, which is why it is dosed into closed heating and cooling circuits and into concrete admixtures to protect reinforcement. In meat curing it is the agent that fixes the pink colour and inhibits Clostridium botulinum. The same reactivity makes it acutely toxic, since nitrite oxidises haemoglobin to methaemoglobin, which cannot carry oxygen, and the lethal dose is small. It must be stored away from acids and from ammonium salts. It is used in corrosion inhibition for closed circuits and concrete, azo dye manufacture, metal phosphating and heat treatment, and in meat curing. Bio Green Chem supplies sodium nitrite to specification on assay, sodium nitrate content, chloride, moisture, insolubles and heavy metals.