Sulphurous acid/sulphur dioxide

Nitrosodisulphonic acid decomposes spontaneously into sulphuric acid, sulphur dioxide and nitric oxide. Its solution is rapidly decolorised on shaking with air or on mixing with hydrogen peroxide, per-mono- or perdi-sulphuric acid, nitric acid, chlorine or potassium chlorate. Most metallic oxides and carbonates decompose the solution, being converted into sulphates.7... 

Properties.—The blue solution is unstable and decomposes slowly, with formation of sulphuric acid, sulphur dioxide and nitrogen dioxide. When shaken with air or submitted to oxidation by chlorine, nitric acid or hydrogen peroxide, conversion into nitrosulphonic acid is effected, brown fumes being liberated. Dilution -with water also destroys the coloured substance. If strongly cooled, the solution changes to an intense red, so that if a solution is too weak to possess a marked colour at the ordinary temperature, the presence of the purple acid can easily be detected by cooling in a mixture of acetone and solid carbon dioxide. 

P. Sabatier found that when nitric acid or nitrogen oxides are dissolved in sulphuric acid containing sulphur dioxide, and the soln. is exposed to moist air, there are indications of the formation of a dark blue compound. If a mixture corresponding with 4N0+02 is passed into sulphuric acid, sat. with sulphur dioxide, and cooled at 0°, the liquid remains colourless, but when water is added very slowly, a dark blue soln. is formed. Similarly, when a mixture of air and nitric oxide is passed into monohydrated sulphuric acid, sat. with sulphur dioxide, and cooled to 0°, the bluish-violet soln. is formed at once with vigorous eServescence. With more cone, sulphuric acid, the liquid is at first colourless, and slowly develops the bluish-violet colour. It was thought by P. Sabatier that peroxylamidosulphonic acid was formed, but there is no real evidence of this. The blue acid decomposes spontaneously into sulphuric acid, sulphur dioxide, and nitric oxide, but it is more stable than E. Fremy s potassium peroxylamidodisulphonate, and does not decompose rapidly even at 100°. 

When it is attacked by hot, concentrated sulphuric acid, sulphur dioxide is evolved ... 

Concentrated nitric acid has little effect on zinc because of the low solubility of zinc nitrate in such a medium. With hot, concentrated sulphuric acid, sulphur dioxide is evolved ... 

Uses.—Sulphur is used principally in the manulacture of gunpowder also to some extent in making sulphuric acid, sulphur dioxide, and mstfrhfli, and for the prevention of fungoid and parasitic growths. 

Substance classes Properties — Effectiveness — Applications 6.2.2 Sulphurous acid/sulphur dioxide HO ... 

In the experiment he found that a mixture of 4 vols. of hepatic gas and 4 vols. of dephlogisticated air gave 2 vols. of volatile sulphureous acid (sulphur dioxide). Austin had found that the solution of sulphur in light inflammable air neither contracts nor expands it , hence 4 vols. of hepatic gas contain 4 vols. of hydrogen, which require at least 2I vols. of oxygen. Of the rest, 2 vols. burnt the sulphur to sulphur dioxide and vol. was used to burn nitrogen as an impurity. Hence the 2 vols. of volatile vitriolic acid (SO2) contain 2 of ox n. 

When zinc, iron, and tin were dissolved in hot undiluted acid of vitriol they evolved uninflammable vapours smelling strongly of the volatile sulphureous acid (sulphur dioxide), and in this case their phlogiston unites to the acid for it is well known, that the volatile sulphureous acid consists of the plain vitriolic acid united to phlogiston . In nitrous (nitric) acid the metals evolved red fumes, produced by the phlogiston uniting with the acid. In a footnote Cavendish says if oil of vitriol be distilled, from sulphur, the liquor which comes over, will be the volatile sulphureous acid. ... 

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