Formation of Sulphur Dioxide

The most important deposits of sulphur in the world arc those of Louisiana and Texas, U.S.A., where //. Franck s method of extraction is followed.2 This obviates the formation of sulphur dioxide and at the same time yields a product of such a degree of purity (in some wells as high as 99-9 per cent.) as to be suitable in most cases for direct use. A boring is made in the earth down to the sulphur stratum so that a continuous pipe can pass thence to the surface the pipe consists of throe concentric tubes (see lig. 1). Superheated water, c.g. at 150" is forced down the annular spaces A, A, between the outer tubes, in order to melt the sulphur in the neighbourhood of the cud of the boring. A blast of heated air down the inmost tube, II, then causes the molten sulphur to be carried up between the two inner tubes to the surface, where it is collected.3... 

Sulphates of the alkali and alkaline earth metals, when heated with sulphur, are converted into sulphide, polysulphide and thiosulphate, with simultaneous formation of sulphur dioxide many other sulphates, e.g. those of copper, mercury, silver and lead, yield only sulphide.7 Other salts of the metals behave in a similar- manner, undergoing transformation into sulphides, the change being effected more readily with the salts of the heavy metals, many of which indeed react slowly with sulphur even at 100° C. in the presence of water.8 At 150° to 200° C. mercuric, stannic and ferric salts in aqueous solution are quantitatively reduced by sulphur mercurous, cupric, bismuth and lead salts arc slowly but quantitatively precipitated as sulphides. Nitrates, permanganates and iodates cause oxidation of the sulphur to sulphuric acid. 

Chemical Properties.—Sulphur monochloride will not burn under ordinary conditions in the air, but when passed through a red-hot tube in the vapour condition and mixed with air or oxygen, combustion occurs, accompanied by a greenish-blue flame and the formation of sulphur dioxide and trioxide, together with chlorine. In contact with water the monochloride undergoes decomposition according to the equation 4... 

When submitted, in a glass vessel, to the electric spark discharge, or when heated to 400° C., gradual decomposition sets in, with formation of sulphur dioxide and fluorine, the latter giving rise to silicon tetrafluoride, and the total change being representable by the equation ... 

At 180° C. thionyl chloride converts sulphur into sulphur mono-chloride, with simultaneous formation of sulphur dioxide, this change in all probability being dependent on the afore-mentioned thermal decomposition 11... 

Like sulphuryl chloride, pyrosulphuryl chloride can convert many elements, e.g. sulphur, phosphorus, antimony and mercury, into the corresponding chlorides, with simultaneous formation of sulphur dioxide and trioxide.2 In the reaction between pyrosulphuryl chloride and phosphorus pentachloride or trichloride, there are obtained phosphorus oxychloride, sulphur dioxide and chlorine. 

It is readily hydrolysed by water. It reacts with organic acids to form acid bromides. Mercury decomposes the vapour with formation of sulphur dioxide. 

By the addition of barium hydroxide to the solution, a solution of barium dithionate can be obtained which, on treatment with the necessary quantity of sulphuric acid, yields a dilute solution of dithionic acid this can be concentrated to some extent by evaporation at the ordinary temperature, but if the concentration is carried too far, decomposition ensues, with formation of sulphur dioxide and sulphuric acid. If so desired, the barium dithionate itself may be isolated by removing the excess of barium hydroxide with a current of carbon dioxide and then allowing the solution to evaporate until crystallisation occurs. 

The bluish-green crystalline mass is very unstable and decomposes fairly rapidly even at the ordinary temperature, giving sulphur dioxide and sulphur. The pure substance may be preserved for several hours in a vacuum. It is hygroscopic, and on absorbing moisture first becomes brown and then deposits sulphur, with concurrent formation of sulphur dioxide, sulphuric acid and possibly other sulphur acids. It is soluble in fuming sulphuric acid, an acid rich in trioxide giving a bluish solution, whilst with less rich acids the solution is brown ordinary pure sulphuric acid causes decomposition. The colour of the brown solution is regarded by some as due to colloidal sulphur formed by partial decomposition of the sesquioxide.6... 

Extraction.—(1) From Pyrites.—In the oxidation of the pyrites (or other sulphur mineral) for the formation of sulphur dioxide in the manufacture of sulphuric acid, foreign elements like arsenic and selenium also undergo oxidation and pass ofC as vapours with the sulphur dioxide. The selenium dioxide produced in this manner their suffers more or less complete reduction by the sulphur dioxide, when finely divided selenium separates, mainly in the lead chambers, as a red, amorphous powder, accompanied possibly by some of the greyish-black form a portion of the dioxide is also found in the Glover tower acid. The amount of selenium in the chamber mud depends, of course, on the nature of the pyrites relatively large quantities of compounds of arsenic, zinc, tin, lead, iron, copper or mercury are always present, arising almost entirely from impurities in the pyrites. 

These reactions accelerate if the solution is heated. Concentrated, hot sulphuric acid dissolves nickel with the formation of sulphur dioxide ... 

Sulphuryl chloride is slowly decomposed by cold water, but hot water or alkalies act rapidly and vigorously, sulphuric acid and hydrochloric acid being formed. When sulphuryl chloride vapour is passed through a tube heated to dull redness, decomposition takes place with formation of sulphur dioxide and chlorine. 

Vhat always happens to a reducing agent (8) To an oxidizing agent (9) Which of the five methods of formation of sulphur dioxide, which you have just tried, do you consider best adapted for preparing the gas in the laboratory for study ... 

Sulphur, if present in pure form, is yellow, but even small amounts of contaminations will make it appear dark. When heated in a porcelain crucible, it first melts, then volatilizes and, if present in larger quantities, bums with a pungent odour, because of the formation of sulphur dioxide. On heating sulphur with concentrated nitric acid, it dissolves with the formation of sulphate ions, which can be identified in the solution (cf. Section 4.24). 

Rapid, reversible migration of the acyl group in 2-acetoxy-3,7-dibenzyltropone and 2-methoxycarbonyl-3,7-dibenzyltropone has been observed tropylium ions (260 R = Me or OMe) are the supposed intermediates. Oxidation of cyclohepta-triene to tropylium ion by fluorosulphonic acid is accompanied by formation of sulphur dioxide, not hydrogen, and therefore must have been effected by reduction of the fluorosulphonic acid (or sulphur trioxide formed by equilibrium dissociation of the fluorosulphonic acid). ... 

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