Sodium Sulfite(redirected from E221)
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Related to E221: E224
sodium sulfite[′sōd·ē·əm ′səl‚fīt]
Na2SO3, a salt; colorless crystals. Density, 2.63 g/cm3. Solubility in water, 20.82 percent at 19.9°C and 21.70 percent at 99°C. At ordinary temperatures Na2SO3.7H2O crystallizes from aqueous solutions.
Sodium sulfite is a strong reducing agent and oxidizes readily in aqueous solutions upon exposure to air. Upon heating in aqueous solutions, Na2SO3 adds sulfur, with the formation of sodium thiosulfate. Sodium sulfate is obtained by the reaction of solutions of Na2CO3 and SO2. It is a component of photographic developers.