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| Names | |
|---|---|
| IUPAC name Calcium hydrogen sulfite | |
Other names
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| Identifiers | |
3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.034.007 |
| E number | E227(preservatives) |
| RTECS number |
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| UNII | |
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| Properties | |
| Ca(HSO3)2 | |
| Molar mass | 202.22 g/mol |
| Melting point | 203 °C |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Calcium bisulfite (calcium bisulphite orcalcium hydrogen sulfite) is aninorganic compound which is thesalt of acalcium cation and abisulfite anion. It may be prepared by treating lime with an excess ofsulfur dioxide and water. As afood additive it is used as apreservative under theE number E227. Calcium bisulfite is anacid salt and behaves like an acid in aqueous solution. It is used in thesulfite process for producing paper from wood chips.[1]
Calcium bisulfite can be prepared by treating lime (chemical formula Ca(OH)2) with an excess ofsulfur dioxide and water.[2] Upon synthesis of calcium bisulfite solution, it will have a green to yellow opaque appearance as an aqueous solution.[3]
When calcium bisulfite reacts with the surrounding air, a crystalline precipitate will form composed ofcalcium sulfite dihydrate.[citation needed]
When calcium bisulfite is digested as a food additive, different reactions in metabolic pathways can result. One common pathway results in a reaction that will yield 6%-8%sulfur dioxide. This can go tosulfite when absorbed by the lungs, and the sulfite will be converted to sulfate in the liver by an enzyme calledsulfite oxidase. Sulfite can be harmful for people susceptible to asthma, leading to asthma attacks. Sulfite can also cause urticaria and angioedema in otherwise healthy individuals.[3]
A process known as wet limestone scrubbing is a means by which sulfur dioxide is removed from the waste emitted during thecombustion offossil fuels. A step in this process is the oxidation of calcium bisulfite to produce sulfate. When this reaction occurs in an aqueous solution,gyspum results. The rate of this reaction can be increased in the presence of magnesium(II) sulfate as a catalyst.[4]
Other catalysts for the oxidation of calcium bisulfite includemanganese,iron,cobalt,nickel,lead, andzinc.[2]
Calcium bisulfite is one of the chemicals used in an overall mild bisulfite treatment meant to increase the sugar yield efficiency in processing timber excess to biofuel andjet fuel. The use of the Mild Bisulfite methodology both increases the yield and also saves cost in shipping wood toethanol plants for processing.[5]
Calcium bisulfite is often used as a food preservative. One such case is to brine cherries. However, research is showing that some microorganisms can cause cherries to rot since they produce the enzymepolygalacturonase that can work even in the presence of calcium bisulfite. Three species of fungi that are especially capable of rotting brined cherries areAspergillus niger,Cytospora leucostoma, andPenicillium expansum.[6]
A calcium bisulfite liquor solution is used in the process of convertingdihydroquercetin in tree bark pulp and then converting dihydroquercetin to a usable form:quercetin. Calcium bisulfite is not the optimum bisulfite compound for this reaction since the calcium ions can be removed from the calcium bisulfite solution during the reaction, thereby inhibiting the mechanism. However, calcium bisulfites, like other bisuflites such asammonium bisulfite, have a catalytic capacity in this reaction since they are not used up and can be reused.[7]
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