Hydrosulphites

Reduction to hydroquinone. Dissolve, or suspend, 0-5 g. of the quinone in 5 ml. of ether or benzene and shake vigorously with a solution of 1 0 g. of sodium hydrosulphite (Na2S204) in 10 ml. of N sodium hydroxide until the colour of the quinone has disappeared. Separate the alkaline solution of the hydroquinone, cool it in ice, and acidify with concentrated hydrochloric acid. Collect the product (extract with ether, if necessary) and recrystalhse it from alcohol or water. 

Sulphur dioxide is used as a preservative for beer, wine and meats in the produetion of sulphites and hydrosulphites in solvent extraetion of lubrieating oils as a general bleaehing agent for oils and foods in sulphite pulp manufaeture in the eellulose and paper industries and for disinfeetion and fumigation. 

Sodium hydrosulphite is unstable. It decomposes violently at 190°C. The interaction with water is particularly dangerous and can cause its ignition. 

The sodium chlorite/sodium hydrosulphite mixture combusts spontaneously. This is explained by the fact that sulphur-containing salts catalyse the decomposition of chlorite. 

Deinked secondary fibers are usually bleached in a bleach tower, but may be bleached during the repulping process. Bleach chemicals may be added directly into the pulper. The following are examples of chemicals used to bleach deinked secondary fibers hypochlorite [HCIO, NaOCl, Ca(OCl)2], hydrogen peroxide (H202), and hydrosulphite (NaHS03). 

Sodium hyposulphite (hydrosulphite) is converted by aldehydes into aldehyde bisulphite compound and aldehyde sulphoxylate ... 

Reducing substances which may combine with atmospheric oxygen, thus removing the ingredient necessary for the explosion of methane, e.g. sodium hydrosulphite. 

The hydrosulphites, M2S204, may be regarded as derived simultaneously from sulphoxylic and sulphurous acids, having the constitution... 

Hydrosulphurous acid is also formed by the action of many metals on sulphurous acid 7 the crust of ferrous sulphite and hydrosulphite formed on the surface of metallic iron is of great protective value in the iron cylinders used for storing liquid sulphur dioxide, which generally contains traces of water.8... 

The decomposition of the polythionic acids (q.v.) in the presence of alkali, the decomposition of hydrosulphites (p. 227) and the hydrolysis of nitrogen sulphide2 by water or aqueous alkali are also processes in which salts of thiosulphuric acid are formed. Certain micro-organisms capable of converting sulphur to thiosulphate have been isolated from soil cultures.3... 

It is possible to prepare the hydrosulphites of the metals in anhydrous condition by the action of various metals, for instance zinc, magnesium, sodium, on sulphur dioxide in the presence of moisture-free ether 4 or alcohol.5 This reaction is of importance as having supplied an early proof of the absence of hydrogen from the salts and hence of the incorrectness of the formula Zn(HSOa)a, NaHS02, which had been accepted previously ... 

Moissan in 1902 obtained anhydrous hydrosulphites by passing sulphur dioxide diluted with hydrogen over the hydrides of the alkali and alkaline earth metals.6 He was able to produce the hydrosulphites of sodium, potassium, lithium, calcium and strontium in this way, and by measurement of the quantity of hydrogen liberated was able to prove the correctness of the general formula Ma.S204 ... 

On pouring the solution into alcohol a double sulphite of sodium and zinc is rapidly precipitated, whilst needles of sodium hydrosulphite, Na9S204.2H20, separate slowly afterwards. Another procedure for the removal of the zinc from the solution is to add milk of lime cautiously, when a solution of sodium hydrosulphite remains.1... 

In the electrolysis of aqueous sulphurous acid or sodium hydrogen sulphite solution, a little hydrosulphite is formed at the cathode as a result of the reduction process.4... 

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