Names | |
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IUPAC name Sodium hydrogen sulfite | |
Other names
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Identifiers | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.028.680 |
E number | E222 (preservatives) |
PubChem CID | |
RTECS number |
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UNII | |
CompTox Dashboard (EPA) | |
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Properties | |
NaHSO3 | |
Molar mass | 104.061 g/mol |
Appearance | White solid |
Odor | Slight sulfurous odor |
Density | 1.48 g/cm3 |
Melting point | 150 °C (302 °F; 423 K) |
Boiling point | 315 °C (599 °F; 588 K) |
42 g/100 mL | |
Refractive index (nD) | 1.526 |
Hazards | |
GHS labelling: | |
H302 | |
P301+P312+P330 | |
NFPA 704 (fire diamond) | |
Flash point | Non-flammable |
NIOSH (US health exposure limits): | |
PEL (Permissible) | none [1] |
REL (Recommended) | TWA 5 mg/m3 [1] |
IDLH (Immediate danger) | N.D. [1] |
Related compounds | |
Other anions | Sodium sulfite Sodium metabisulfite Sodium biselenite |
Other cations | Potassium bisulfite |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the approximate chemical formula NaHSO3. Sodium bisulfite is not a real compound, [2] but a mixture of salts that dissolve in water to give solutions composed of sodium and bisulfite ions. It appears in form of white or yellowish-white crystals with an odor of sulfur dioxide. Regardless of its ill-defined nature, sodium bisulfite is used in many different industries such as a food additive with E number E222 in the food industry, a reducing agent in the cosmetic industry, and a decomposer of residual hypochlorite used in the bleaching industry. [3] [4] [5]
Sodium bisulfite solutions can be prepared by treating a solution of suitable base, such as sodium hydroxide or sodium bicarbonate with sulfur dioxide.
Attempts to crystallize the product yield sodium metabisulfite (also called sodium disulfite), Na2S2O5. [6]
Upon dissolution of the metabisulfite in water, bisulfite is regenerated:
Sodium bisulfite is formed during the Wellman-Lord process. [7]
The safety of cosmetic products is constantly in question as the components are always changing or being discovered as a possibly harmful substance. The sulfite components of cosmetic ingredients, such as sodium bisulfite, underwent clinical trials to find out their safety in cosmetic formulations. Sodium bisulfite functions as a reducing agent and furthermore as a hair-waiving/straightening agent. [8] As of 1998, sodium bisulfite was used in 58 different cosmetic products including hair conditioners, moisturizers, and hair dyes. [9]
In a cosmetic context, the reducing ability of sodium bisulfite is used to prevent discoloration, bleach food starches, and delay spoilage of the product. Since the sulfite molecule was used in so many compounds in the 1990s, the EPA, FDA, and American Conference of Governmental Industrial Hygienists established a working place threshold limit value for sulfur dioxide of 2ppm averaged over 8 hours, and a 3-hour level of 5ppm. Even with this threshold established, the FDA recognized sodium bisulfite as a "generally recognized as safe" compound. [3]
A final examination on the carcinogenicity, genotoxicity, oral toxicity, and cellular toxicity on consumed sodium bisulfite was conducted using living subjects such as mice and rats. The International Agency for Research on Cancer concluded that there was inadequate evidence that sodium bisulfite was carcinogenic. [3] Under specific conditions such as acidity and concentration level, sodium bisulfite was able to cause negative alterations to the genome such as catalyzing transamination, and induce sister-chromatid exchanges suggesting possible genotoxicity. [10] In a study using Osbourne-Mendel strain rats, it was concluded that oral toxicity was not significant if the consumed concentration was less than 0.1% (615ppm as SO2). [11] A study done by Servalli, Lear, and Cottree in 1984 found that sodium bisulfite did not produce membrane fusion in hepatic and murine glial cells and human fibroblasts so there is no oral toxicity. These clinical studies concluded that sodium bisulfite was safe to use in cosmetic formulations. [3]
Similar to the cosmetic industry, the European Commission requested the European Food Safety Authority (EFSA) to review and determine if the use of sulfites as food additives was still safe in light of new scientific technology and information. Since sodium bisulfite is a known sulfonating compound, it underwent the experimentation. Based on clinical experiments using rats and mice, the World Health Organization Expert Committee on Food Additives came to the conclusion that 0-0.7mg of sulfur dioxide equivalent/kg of body weight per day will cause no harm to an individual consuming this compound as a food additive. The genotoxicity and carcinogenicity were examined just as in the cosmetic trials and in both cases, no potential for concern with respect to the sulfites were found. [5]
The production of sodium bisulfite used as a food additive can be described by the combination of sulfur dioxide gas with aqueous sodium hydroxide solution in usual absorber apparatuses. In order to analyze the amount of free sulfites in food as a result of the sulfonation of sodium bisulfite, multiple methods can be used including the Monier-Williams type procedure, [12] HPLC after extraction, and Flow Injection analysis. Overall, the use of sodium bisulfite in the food industry as an additive and antioxidant is safe and beneficial to the lifespan of processed foods. [5]
An antichlor is a substance used to decompose residual hypochlorite or chlorine after chlorine-based bleaching, in order to prevent ongoing reactions with, and therefore damage to, the material that has been bleached. Sodium bisulfite is an example of an antichlor. Historically, sodium bisulfite has been used in the textile industry, cosmetic industry, food industry, and more. [3] [4]
Antichlors are very useful in the textile industry because bleaching of compounds using chlorine is a standard practice. However, the use of sodium bisulfite in the decomposition of excess hypochlorite can lead to harmful byproducts when it comes into contact with water at the concentrations present for industrial use. [4] Contact with these dangerous byproducts or even strong concentrations of sodium bisulfite can be harmful to the environment and contact with the skin. Strong concentrations of these compounds can contaminate ecosystems, harm animals, and cause contact dermatitis with industrial workers. [4] [13] The concentrations that could result in these outcomes are much stronger than the concentrations discussed in the cosmetic and food industry.
Sulfur dioxide or sulphur dioxide is the chemical compound with the formula SO
2. It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of sulfur-bearing fossil fuels.
Sodium hypochlorite is an alkaline inorganic chemical compound with the formula NaOCl. It is commonly known in a dilute aqueous solution as bleach or chlorine bleach. It is the sodium salt of hypochlorous acid, consisting of sodium cations and hypochlorite anions.
Sulfites or sulphites are compounds that contain the sulfite ion, SO2−
3. The sulfite ion is the conjugate base of bisulfite. Although its acid is elusive, its salts are widely used.
Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound of chemical formula Na2S2O5. The substance is sometimes referred to as disodium metabisulfite. It is used as a disinfectant, antioxidant, and preservative agent. When dissolved in water it forms sodium bisulfite.
Sodium sulfite (sodium sulphite) is the inorganic compound with the chemical formula Na2SO3. A white, water-soluble solid, it is used commercially as an antioxidant and preservative. It is also suitable for the softening of lignin in the pulping and refining processes of wood and lignocellulosic materials. A heptahydrate is also known but it is less useful because of its greater susceptibility toward oxidation by air.
Sodium thiosulfate is an inorganic compound with the formula Na2S2O3·(H2O)x. Typically it is available as the white or colorless pentahydrate, which is a white solid that dissolves well in water. The compound is a reducing agent and a ligand, and these properties underpin its applications.
Sodium dithionite is a white crystalline powder with a sulfurous odor. Although it is stable in dry air, it decomposes in hot water and in acid solutions.
Sodium dithionate Na2S2O6 is an important compound for inorganic chemistry. It is also known under names disodium dithionate, sodium hyposulfate, and sodium metabisulfate. The sulfur can be considered to be in its +5 oxidation state.
The bisulfite ion (IUPAC-recommended nomenclature: hydrogensulfite) is the ion HSO−
3. Salts containing the HSO−
3 ion are also known as "sulfite lyes". Sodium bisulfite is used interchangeably with sodium metabisulfite (Na2S2O5). Sodium metabisulfite dissolves in water to give a solution of Na+HSO−
3.
Potassium metabisulfite, K2S2O5, also known as potassium pyrosulfite, is a white crystalline powder with a pungent odour. It is mainly used as an antioxidant or chemical sterilant. As a disulfite, it is chemically very similar to sodium metabisulfite, with which it is sometimes used interchangeably. Potassium metabisulfite has a monoclinic crystal structure.
Bleach is the generic name for any chemical product that is used industrially or domestically to remove colour (whitening) from fabric or fiber or to disinfect after cleaning. It often refers specifically to a dilute solution of sodium hypochlorite, also called "liquid bleach".
Potassium bisulfite (or potassium hydrogen sulfite) is a chemical mixture with the approximately correctly mentioned formula chemical formula KHSO3. Potassium bisulfite in fact is not a real compound, but a mixture of salts that dissolve in water to give solutions composed of potassium ions and bisulfite ions. It is a white solid with an odor of sulfur dioxide. Attempts to crystallize potassium bisulfite yield potassium metabisulfite, K2S2O5.
The sulfite process produces wood pulp that is almost pure cellulose fibers by treating wood chips with solutions of sulfite and bisulfite ions. These chemicals cleave the bonds between the cellulose and lignin components of the lignocellulose. A variety of sulfite/bisulfite salts are used, including sodium (Na+), calcium (Ca2+), potassium (K+), magnesium (Mg2+), and ammonium (NH4+). The lignin is converted to lignosulfonates, which are soluble and can be separated from the cellulose fibers. For the production of cellulose, the sulfite process competes with the Kraft process which produces stronger fibers and is less environmentally costly.
Calcium sulfite, or calcium sulphite, is a chemical compound, the calcium salt of sulfite with the formula CaSO3·x(H2O). Two crystalline forms are known, the hemihydrate and the tetrahydrate, respectively CaSO3·½(H2O) and CaSO3·4(H2O). All forms are white solids. It is most notable as the product of flue-gas desulfurization.
Calcium bisulfite is an inorganic compound which is the salt of a calcium cation and a bisulfite anion. It may be prepared by treating lime with an excess of sulfur dioxide and water. As a food additive it is used as a preservative under the E number E227. Calcium bisulfite is an acid salt and behaves like an acid in aqueous solution. It is used in the sulfite process for producing paper from wood chips.
The Wellman–Lord process is a regenerable process to remove sulfur dioxide from flue gas without creating a throwaway sludge product.
A disulfite, commonly known as metabisulfite or pyrosulfite, is a chemical compound containing the ion S
2O2−
5. It is a colorless dianion that is primarily marketed in the form of sodium metabisulfite or potassium metabisulfite. When dissolved in water, these salts release the hydrogensulfite HSO−
3 anion. These salts act equivalently to sodium hydrogensulfite or potassium hydrogensulfite.
Ammonium sulfite is the ammonium salt of sulfurous acid with the chemical formula (NH4)2SO3.
Chlorine-releasing compounds, also known as chlorine base compounds, is jargon to describe certain chlorine-containing substances that are used as disinfectants and bleaches. They include the following chemicals: sodium hypochlorite, chloramine, halazone, and sodium dichloroisocyanurate. They are widely used to disinfect water and medical equipment, and surface areas as well as bleaching materials such as cloth. The presence of organic matter can make them less effective as disinfectants. They come as a liquid solution, or as a powder that is mixed with water before use.
The topic of sulfite food and beverage additives covers the application of sulfites in food chemistry. "Sulfite" is jargon that encompasses a variety of materials that are commonly used as preservatives or food additive in the production of diverse foods and beverages. Although sulfite salts are relatively nontoxic, their use has led to controversy, resulting in extensive regulations. Sulfites are a source of sulfur dioxide (SO2), a bactericide.