Sodium hydrosulfite. Physical and chemical properties. Application
Sodium hydrosulfite is an inorganiccompound, acid salt of sodium and sulfurous acid, preservative (E222) and antioxidant. Possesses bleaching properties. Has the following chemical formula: NaHSO3.
Physical properties of sodium hydrosulfite:
1. It is a white powder with a faint grayish shade.
2. The molar mass is 104.061 g / mol, the density is 1.48 g / cm3.
3. The melting point is 150 degrees Celsius.
4. It dissolves well in water (H2O) and in dilute alkalis.
Chemical properties of sodium hydroxide:
1. Decomposes on heating:
2NaHSO3 (sodium hydrosulfite) = Na2SO3 (sodium sulfite) + SO2 (sour gas, released as gas) + H2O (water)
2. Decomposed by acids:
NaHSO3 + HCl (hydrochloric acid) = NaCl (sodium chloride) + SO2 (sour gas) + H2O (water)
3. It is decomposed by alkalis:
NaHSO3 + NaOH (hydroxide) = Na2SO3 (sodium sulfite) + H2O (water)
4. Oxidized with oxygen:
4NaHSO3 + O2 = 2Na2SO4 (sodium sulfate) + 2SO2 (sulfur dioxide, volatilized) + H2O (water)
How is sodium hydrosulfite obtained?
This substance can be obtained in the following ways:
1. By the reaction of sodium hydroxide with sulfur oxide:
NaOH (sodium base) + SO2 (sulfur oxide) = NaHSO3 (sodium hydrosulfite)
2. By 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, precipitates) + NaCl (sodium chloride)
3. Using a reaction in which sodium dithionite reacts, water and oxygen:
2Na2S2O4 (sodium dithionite in diluted form) + 2H2O (water) + O2 (oxygen) = 4NaHSO3 (sodium hydrosulfite)
Application of sodium hydrosulfite:
- light, chemical and other industries;
- in the food industry is used as an antioxidant or preservative;
- used in almost all wines exported (the chemical properties of sodium hydrosulfite in this case help to prevent oxidation and preserve the taste of the drink);
- is used for canning fruits to fight microbes and prevent darkening;
- when dyeing and bleaching various tissues is used as a preservative;
- for removal of active dyes in the process of dyeing cotton;
- for polyester dyeing for reconstitution;
- as a preservative in the bleaching of tissues and as a reducing agent for vat dyes;
- in biochemical engineering is used to maintain anaerobic conditions in the reactor.
Is sodium hydrogen sulfite toxic to humans?
The substance we are considering in excessiveconcentrations may cause serious allergic reactions. Since the year 1999, NaHSO3 (like potassium hydrosulfite, E 228) is banned in the United States of America for use on raw fruits and vegetables after a number of deaths. Sodium hydrosulfite causes various ailments of the digestive system. According to the EU Directive on substances hazardous to humans, the E 222 additive belongs to the group of hazardous chemical compounds. In Ukraine and the Russian Federation, this substance is authorized for use only with strict observance of technologies.
Use of sodium hydrogen sulphate in the food industry
This substance in the food industryis used under the name E 222. This is a food additive of synthetic origin, which has a high level of danger. With long systematic use, it causes serious damage to the body. Due to the property of inhibiting reproduction and growth of microorganisms and bacteria, it is used as an antioxidant and preservative. In acidic environment, sodium hydrosulfite decomposes into sulfur-containing compounds and sulfur itself.
First aid measures for poisoning
Rest and warmth, dry and clean clothes, as well as fresh air are recommended. Skin and eyes should be washed with cool water. In case of burns, an aseptic bandage should be applied. Then call an ambulance.