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. It is a precursor to a variety of organic compounds, such as pharmaceuticals, dyes, and pesticides, but it is probably best known as a food additive used in processed meats and (in some countries) in fish products. Uses
Industrial chemistry
The main use of sodium nitrite is for the industrial production of organonitrogen compounds. It is a reagent for conversion of amines into diazo compounds, which are key precursors to many dyes, such as diazo dyes. Nitroso compounds are produced from nitrites. These are used in the rubber industry.It is used in a variety of metallurgical applications, for phosphatizing and detinning.Sodium nitrite is an effective corrosion inhibitor and is used as an additive in industrial greases, as an aqueous solution in closed loop cooling systems, and in a molten state as a heat transfer medium. Food additive and preservative
Sodium nitrite is used to speed up the curing of meat and also impart an attractive pink color. Nitrite reacts with the meat myoglobin to cause color changes, first converting to nitrosomyoglobin (bright red), then, on heating, to nitrosohemochrome (a pink pigment).Historically, salt has been used for the preservation of meat. The salt-preserved meatproduct was usually brownish-gray in color.
2
          
          
            NaNO
            
              2
            
            
              
            
          
          ⟶
          
            Na
            
              2
            
            
              
            
          
          O
          +
          NO
          +
          
            NO
            
              2
            
            
              
            
          
        
      
    
    {\displaystyle {\ce {2 NaNO2 -> Na2O + NO + NO2}}}
  Sodium nitrite can also be used in the production of nitrous acid:

  
    
      
        
          2
          
          
            NaNO
            
              2
            
            
              
            
          
          +
          
            H
            
              2
            
            
              
            
          
          
            SO
            
              4
            
            
              
            
          
          ⟶
          2
          
          
            HNO
            
              2
            
            
              
            
          
          +
          
            Na
            
              2
            
            
              
            
          
          
            SO
            
              4
            
            
              
            
          
        
      
    
    {\displaystyle {\ce {2NaNO2 + H2SO4 ->2 HNO2 + Na2SO4}}}
  The nitrous acid then, under normal conditions, decomposes:

  
    
      
        
          2
          
          
            HNO
            
              2
            
            
              
            
          
          ⟶
          
            NO
            
              2
            
            
              
            
          
          +
          NO
          +
          
            H
            
              2
            
            
              
            
          
          O
        
      
    
    {\displaystyle {\ce {2 HNO2 -> NO2 + NO + H2O}}}
  The resulting nitrogen dioxide hydrolyzes to a mixture of nitric and nitrous acids:

  
    
      
        
          2
          
          
            NO
            
              2
            
            
              
            
          
          +
          
            H
            
              2
            
            
              
            
          
          O
          ⟶
          
            HNO
            
              3
            
            
              
            
          
          +
          
            HNO
            
              2
            
            
              
            
          
        
      
    
    {\displaystyle {\ce {2 NO2 + H2O -> HNO3 + HNO2}}}

Isotope labelling 15N
In organic synthesis isotope enriched sodium nitrite-15N can be used instead of normal sodium nitrite as their reactivity is nearly identical in most reactions.