Hyposulphuric Acid

This acid is unknown in the separate state. Its salts are formed when sulphur is boiled with a solution of a sulphite. Thus, if sulphite of soda is boiled with sulphur, we have NaO, SO, + S=NaO, S O. The salts of this acid are called hyposulphites, and they are all, except the hyposulphite of baryta, easily soluble in water. Hyposulphites are also formed when alkalies are fused at a low heat with sulphur, and when solutions of alkaline sulphurets are exposed to the air so as to be slowly oxidised. 

When we attempt to separate hyposulphurous acid from any of its salts, it is instantly resolved into sulphurous acid and sulphur, 8303=80,-1-8. When oxidised by nitric acid, the hyposulphites are converted into bisnlphates, KO, S,0 -1-0 = KO, 280,. 

This acid is formed, along with sulphuric acid, when sulphurous acid is oxidised by means of peroxide of manganese 380,- -2MnO, =MnO, S3O. -)-MnO, SO3. The solution thus obtained is decomposed by baryta, or by sulphuret of barium, by which the manganese is separated as oxide or as sulphuret, and the sulphuric acid as sulphate of baryta, and hyposulphate of baryta, a soluble salt, is obtained MnO,8 0 -l-BaS=BaO, SjO d-MnS and MnO, 80,-1-BaS=BaO, 803-t-MnS. The filtered solution is then mixed %vith just as much diluted sulphuric acid as is sufficient to separate the 

When concentrated by evaporation in vacuo, hyposulphuric acid forms a syrupy liquid of a very acid taste, and devoid of smell. When heated, it yields sulphurous acid gas, while sulphuric acid remains, S,0, = SO,-f SO,. Its salts, when Ignited, give oif sulphurous acid, white sulphates remain MO, S,0,=S0,-)-M0, SO,. 

With bases, this acid forms salts, most of which crystallise with great facility. It is not applied to any useful purpose. 

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The various kinds of alkali, cf commerce usually contain a. greater or less proportion of chlorides and sulphates. The presence of these dees not interfere In the slightest degree with the above methods of estimation. In some cases, however, sulphides, sulphites, and hyposulphites aro also present, and these, neutralizing a certain quantity of the tost acjd, Tender the determinations more or less inaccurate. The first of these salts evolves sulphide of hydrogen, the second sulphurous acid, and the last hyposulphurous acid, which is immediately decomposed into sulphurous ecitl... 

Hyposulphite of soda, and other soluble salts of hyposulphurous acid, possess the remarkable property of dissolving all the compounds of silver, even the chloride, and the solution thus formed has a very intense sweet taste, with a metallic after-taste. This property has been made available in the dagaerreotype, for the purpose of dissolving the sensitive coating of iodide from the plate of eilver alter exposure to light, aud thus fixing the image already formed. For this purpose hyposulphite of soda is now prepared on a very considerable scale. 

Aqueous solutions of the salts, or of tellurium dioxide in acids, easily undergo reduction.to elementary tellurium. Phosphorus, phosphorous acid,-7 hypophosphorous acid,8 sulphurous acid,9 thiosulphuric acid,10 hyposulphurous acid,11 hydriodic acid,12 hydrogen sulphide,13 ferrous salts, stannous salts,14 hydrazine 15 and phenylhydrazine, as well as various metals,18 e.g. zinc, iron, tin, cadmium, antimony and copper, are able to effect this reduction. 

This compound is obtained by oxidation of dimethylparaphenylenediamine in presence of sodium hyposulphite, or by action of hyposulphurous acid (thiosulphuric acid, H2S2O3) on the red oxidation product of dimethylparaphenylenediamine. Two processes may be employed for the manufactnre of methylene blue from this compound. (1) The thiosulphonic acid is oxidised with dimethyl-aniline, whereby an insoluble compound ... 

The reducing-agents more commonly employed are ferrous salts, arsenious acid, stannous oxide, hyposulphurous acid, zinc powder, and grape-sugar. 

Since the equivalent of a compound body is the sum of the equivalents of its constituents, it follows, that if we know the equivalent of a compound and the relative proportions by weight of its component parts, we can calculate the number of equivalents of each element contained in the compound. For example, we find by analysis, that 100 grains of hyposulphuric acid are composed of 44 59 grains sulphur, and55 41 grains oxygen. We also find, by experiment, that the equivalent of hyposulphuric... 

When chloride of sulphur, SCI, acts on dry ammonia, NH, a compound is formed, SCI, 2 NH,. By the action of water on this there is formed, among other products, a greenish yellow solid body, which is sulphuret of nitrogen NS,. By contact with water, it is gradually converted into hyposulphurous acid and ammonia for 2 NS, + 6 H 0 = 2 NH, -f 3 S, 0,. (Soubeiran). 

When an excess of chlorine is passed through the preceding compound, and the liquid is repeatedly distilled at about 140", the protochloride is obtained pure. It is a deep reddish brown liquid, which boils at 147°. Its Sp. G. is 1 62 that of its vapour, 3 68. When acted on by water, it yields hydrochloric acid and hyposulphurous acids, the latter being soon spontaneously decomposed, 2SCl-l-2HO=z2HCl-l-S, 0,. 

Gay-Lussac and Welter discovered dithionic acid (H2S20e). The name thionic acids , and the modern name dithionous acid for hyposulphurous acid, were proposed by Berzelius. Trithionic acid was discovered by Lan-glois and investigated by Mathieu Plessy, who gave a better method of preparation. Sodium tetrathionate was discovered by Fordos and Gelis. Pentathionic acid was discovered by Wackenroder (see p. 904). 

Berthollet and W. Higgins found that iron dissolves in sulphurous acid without evolution of gas (Stahl had noticed this in 1718 see Vol. II, p. 680) and Fourcroy and Vauquelin found the same result with zinc and tin. Schonbein showed that a peculiar acid, hyposulphurous acid, is formed, also by electrol)Ttic reduction of sulphurous acid its salts were investigated by Schiitzenberger, who thought the sodium salt was NaHS02 the correct formula Na2S204 was found by Bernthsen. ... 

In order to prepare hyposulphurous acid a dilute solution of oxalio arid is added to a solution of a hyposulphite a yellow liquid is then obtained which soon decomposes, thiosul-phttrio acid being formed, and this being-very unstable decomposes into sulphur and siriphur dioxide. 

Still in France) S O is one atom of hyposulphuric acid (dithionic anhydride) 2 5... 

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