Sodium metabisulphite

Transfer of an active chemical agent in an inherently safer form (e.g. sulphur dioxide as sodium metabisulphite, chlorine as sodium hypochlorite). Generation of an active agent in this manner clearly reduces the inventory in use. 

Sodium disulphite solution (sodium metabisulphite). Dissolve 0.5 g of the solid reagent (Na2S205) in 10 mL water. Prepare fresh daily. 

Chemical stability. Some medicaments undergo chemical change in aqueous soluhons. If the change is due to oxidation, a reducing agent such as sodium metabisulphite is included (e.g. Adrenaline Injection BP). 

Wedzicha, B.L., Chemistry of Sulphur Dioxide in Foods, Elsevier, Amsterdam, 1984. Damant, A., Reynolds, S., and Macrae, R., The structural identification of a secondary dye produced from the reaction between sunset yellow and sodium metabisulphite, FoodAddit. Contam., 6, 273, 1989. 

Japanese workers have described a stable aqueous solution of neomycin with the incorporation of a borate buffer (pH 6) and E.D.T.A.295 The presence of 1-10% of glycerol, propylene glycol or mannitol has been claimed to improve the solution appearance by preventing discoloration29°. The presence of polyols also prevented a decrease in pH value of the solution. Discoloration may also be prevented by addition of 0.1% sodium metabisulphite at a solution pH of 6.6 to 6.8297. 

Finally, in a method originated by Witt [22], which is occasionally useful for the diazotisation of stable amines of high relative molecular mass that pose solubility problems, the amine is dissolved in nitric acid before the addition of sodium metabisulphite. Nitrous acid is produced in the medium according to Scheme 4-9, enabling diazotisation to proceed. 

Methylaminophenol-sulphite Solution Dissolve 0.1 g of 4-methylaminophenol sulphate, 20 g sodium metabisulphite and 0.5 g anhydrous sodium sulphite in sufficient DW to produce 100 ml. 

Theory Sodium metabisulphite in acidic medium (HC1) yields S02 which reacts with water to produce sulphurous acid. The generated sulphurous acid is quantitatively oxidized by iodine to sulphuric acid, and the excess iodine is subsequently back titrated with sodium thiosulphate. The various reactions can be expressed as shown below ... 

Materials Required Sodium metabisulphite 0.2 g 0.1 N Iodine solution hydrochloric acid ( 11.5 N) 1 ml 0.1 N sodium thiosulphate starch solution. 

Procedure Weigh accurately about 0.2 g of sodium metabisulphite and dissolve in 50.0 ml of 0.1 N iodine solution and add 1 ml hydrochloric acid. Titrate the excess of iodine with 0.1 N sodium thiosulphate employing freshly prepared starch solution, added towards the end of the titration, as indicator. Each ml of 0.1 N iodine is equivalent to 0.0047453 g of Na Oj. 

The trichlorides obtained by the alkoxytellurination of alkenes (see Section 3.5.1.2) or by the cyclotellnrination of hydroxyaUcenes (see Section 4.6.2.4) are reduced in situ, without isolation, with sodium metabisulphite. ... 

Pal BB, Bhunya SP Genotoxic effect of a preservative, sodium metabisulphite as revealed... 

The 2 6-dimethylcycZotelluropentane-3 5-dione required for this preparation is obtained from the corresponding dichloride by reduction with sodium metabisulphite. Condensation with hydroxylamine sulphate then gives the dioxime, which separates from hot dilute alcohol as pale yellow needles, decomposing at 168° to 170° C., insoluble in water, but freely dissolving in aqueous sodium hydroxide. 

The presence of sodium nitrate in the nitrite used has a harmful effect on the stability of nitroso compounds. This action may be minimised by the addition of reducing agents, e.g., sodium metabisulphite. (J. Soc. Dyer., 41, 275.)... 

Commercial sodium nitrite contains 1—3% sodium nitrate, the harmful effect of which on diazonium compounds may be obviated by adding to the amine solution or the nitrite solution an amount (1-5—4 5% of the weight of nitrite used) of sodium metabisulphite slightly in excess of that necessary to reduce the nitrate. Diazonium compounds prepared in this way or with pure sodium nitrite are much more stable (J. Soc. Dyers, 41, 275.)... 

Sodium bisulphite solution may be obtained by dissolving the sodium bisulphite in water, but the solution so prepared does not act so readily with aldehydes and ketones as the syrupy apple-green solution described above. A freshly prepared solution should always be used for aldehydes and ketones. A saturated solution of sodium metabisulphite (Na Os) is also applicable. 

Solid-phase extraction is routinely used to clean up extracts prior to quantitation (19,42,70, 80-82). Alternatively, endogenous fluorescent artifacts in food samples can be eliminated by oxidation with potassium permanganate/hydrogen peroxide/sodium metabisulphite. Benzyl alcohol has been used to extract riboflavin selectively without the coenzymes, permitting the determination of free riboflavin. 

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