Sodium hydrosulfite is an inorganic compound, an acid salt of sodium metal and sulfur dioxide, a preservative (E222) and an antioxidant. It has whitening properties. It has the following chemical formula: NaHSO3.
Physical properties of sodium hydrosulfite:
1. It is a white powder with a faint grayish tint.
2. The molar mass is 104.061 gram / mol, the density is 1.48 gram / centimeter³.
3. The melting point is 150 degrees Celsius.
4. It is well soluble in water (H2O) and in dilute alkalis.
Chemical properties of sodium hydroxide:
1. It decomposes on heating:
2NaHSO3 (sodium hydrosulfite) = Na2SO3 (sodium sulfite) + SO2 (sulfur dioxide, liberated as gas) + H2O (water)
2. It is decomposed by acids:
NaHSO3 + HCl (hydrochloric acid) = NaCl (sodium chloride) + SO2 (sulfur dioxide) + H2O (water)
3. It is decomposed by alkalis:
NaHSO3 + NaOH (hydroxide) = Na2SO3 (sodium sulfite) + H2O (water)
4. Oxidized by oxygen:
4NaHSO3 + O2 = 2Na2SO4 (sodium sulfate) + 2SO2 (sulfur dioxide, volatilizes) + H2O (water)
How to get sodium hydrosulfite?
This substance can be obtained in the following ways:
1. By the interaction of sodium hydroxide with sulfur oxide:
NaOH (sodium base) + SO2 (sulfur oxide) = NaHSO3 (sodium hydrosulfite)
2. Through the reaction (at room temperature) of sodium dithionite with water and hydrochloric acid:
2Na2S2O4 (sodium dithionite) + H2O (water) + HCl (hydrochloric acid) = 2NaHSO3 (sodium hydrosulfite) + S (sulfur, precipitated) + NaCl (sodium chloride)
3. Using a reaction in which sodium dithionite, water and oxygen interact:
2Na2S2O4 (diluted sodium dithionite) + 2H2O (water) + O2 (oxygen) = 4NaHSO3 (sodium hydrosulfite)
The use of sodium hydrosulfite:
- light, chemical and other industries;
- in the food industry is used as an antioxidant or preservative;
- It is used in almost all wines exported (the chemical properties of sodium hydrosulfite in this case help prevent oxidation and preserve the taste of the drink);
- It is used when preserving fruits to combat microbes and prevent darkening;
- during dyeing and bleaching of various tissues it is used as a preservative;
- to remove active dyes in the process of dyeing cotton;
- when dyeing polyesters for reconditioning;
- as a preservative in bleaching fabrics and as a reducing agent for vat dyes;
- in biochemical engineering is used to maintain anaerobic conditions in the reactor.
Is sodium hydrosulfite toxic to humans?
The substance we are considering in excessive concentrations can cause serious allergic reactions. Since nineteen eighty, NaHSO3 (like potassium hydrosulfite, E 228) has been banned in the United States of America from being used on raw fruits and vegetables after a number of fatalities. Sodium hydrosulfite causes various ailments of the digestive system. According to the directive of the European Union on substances that are dangerous to humans, additive E 222 belongs to the group of hazardous chemical compounds. In Ukraine and the Russian Federation, this substance is approved for use only with strict adherence to technology.
The use of sodium hydrogen sulfate in the food industry
This substance is used in the food industry under the name E 222. It is a dietary supplement of synthetic origin with a high level of danger. With prolonged systematic use, it causes serious harm to the body. Due to its ability to inhibit the reproduction and growth of microorganisms and bacteria, it is used as an antioxidant and preservative. In an acidic environment, sodium hydrosulfite decomposes into sulfur-containing compounds and sulfur itself.
First Aid Measures for Poisoning
Rest and warmth, dry and clean clothes, and also fresh air are recommended. Rinse skin and eyes with cool water. For burns, an aseptic dressing should be applied. Next call an ambulance.