Sodium hyposulphite

It is interesting to note that azo dyestuffs may be conveniently reduced either by a solution of stannous chloride in hydrochloric acid or by sodium hyposulphite. Thus phenyl-azo-p-naphthol 3delds both aniline and a-amino-p-naphthol (see formula above), and methyl orange gives p-aminodimethylaniline and sulphanilic acid ... 

Sodium hyposulphite (dithionite) NajS O, may also bo employed for the reduction see under Methyl Orange, Section IV,78. 

Method 2. Suspend 2-0 g. of methyl orange in 4 ml. of water, and add a small quantity of sodium hyposulphite (Na2S204). Heat the mixture and add more sodium hyposulphite until the colour is discharged. The sulphanilic acid remains in the solution as sodium sulphanilate and the p-aminodimethyl-aniline may be extracted with ether as in Method 1. 

Place 20 g. of Orange II (Section IV,79) in a 600 ml. beaker and dissolve it in 250 ml. of water at 40-50°. Add, with stirring, 24-25 g. of sodium hyposulphite (Na SjO ) this discharges the colour and yields a pink or cream-coloured, finely-divided precipitate of a-amino-p-naphthol (compare Section IV,76). Heat the mixture nearly to boiling until it commences to froth considerably, then cool to 25° in ice, filter on a... 

Hydroperoxides decompose in a bimolecular reaction with the formation of water. The activation energy of the peroxide decomposition reaction could be reduced by using some activators, i.e., Fe2+, Cu2+ and sodium hyposulphite, etc. 

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

Sodium Hyposulphite ( Hydrosulphite, Na2S204).—S02 is passed into a strong solution of NaHSOs until saturated, and the mixture reduced with zinc dust. 

L. G. de St. Martin, and 0. Pettersson and A. Hogland employed a soln. of sodium hyposulphite for absorbing oxygen—vide also the work of C. Brunner, and N. Dumouiin. 

Sodium hyposulphite, Na2S204.—The hyposulphite was first prepared in solution by Schiitzenberger4 by reducing a solution of sodium hydrogen sulphite with zinc, but the yield is unsatisfactory. Bemthsen and Bazlen5 obtained the pure substance by reducing the primary sulphite with zinc-dust in presence of sulphurous acid,... 

A laboratory method 2 for the preparation of sodium hyposulphite depends on the interaction of sodium formaldehydesulphoxylate,3 NaCH303S,2H20, and sodium hydrogen sulphite, the product having a purity of 80 to 85 per cent., and the yield being 55 to 60 per cent, of that theoretically possible. The sodium formaldehydesulphoxylate can be obtained2 by the reduction of commercial hydro-sulphite by zdnc-dust and zinc oxide in presence of formaldehyde solution, the crude product being recrystallized from water at 70° C. 

Sodium hyposulphite dihydrate forms colourless vitreous prisms, readily soluble in water. On heating it loses its water of crystallization, melts at red heat, and burns with a blue flame, evolving sulphur dioxide. On addition of acid in small proportion the solution develops a red colour, due to separation of sulphur. Molecular-weight determinations by the cryoscopic method indicate it to be the salt of a dibasic acid, and to be represented by the formula Na2S204.4... 

Hydrogen sulphide has no action on dry sodium hyposulphite, but in presence of water it reacts as indicated by the equation... 

The sulphur is obtained in a weighable form, and Sinnatt6 advocates the estimation of sodium hyposulphite by this method. 

Sodium hyposulphite is oxidized by iodine to sodium hydrogen... 

The action of selenium and tellurium on sodium hyposulphite has been investigated by Tschugaev and Chlopin.2... 

Sodium selenides.—The monoselenide, Na2Se, is formed by the action of selenium on a solution of excess of sodium in liquid ammonia, and separates out.6 It can also be produced by the interaction of selenium and sodium hyposulphite, Na2S204.6 It melts above 875° C., and on exposure to air its solution in water acquires a reddish colour, and deposits selenium. In solution it is extensively hydrolyzed, and under these conditions may be regarded as a mixture of sodium hydrogen selenide, NaSeH, and sodium hydroxide. Four hydrates are known, with 4, 9, 10, and 16 molecules of water respectively.7 For the heat of formation of the anhydrous compound Fabre8 gives 59 7 Cal., and for the heat of solution at 14° C., 18-6 Cal. He has also investigated the heat of solution of the hydrates. 

Cuprous oxide is produced in the form of an orange-yellow, amorphous gel containing water by the reduction of an alkaline cupric solution with sodium hyposulphite 7... 

The dioxide is also formed by suitable reduction of chromates, for examjole, by means of sodium hyposulphite, alcohol, nitric oxide, or a mixture of nitric and oxalic acids or by interaction of chromic chloride and bleaching powder. ... 

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