Sulphur dioxide as a solvent

Liquid Sulphur Dioxide as a Solvent of Sulphur Trioxide... 

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A. Halogeno-derivatives.—Interest in the reactivity of trichlorophos-phazenyl derivatives, RN=PCl3, which may exist as monomers or cyclic dimers, has been sustained. Previous findings on the reactivity of the dimers (18) to sulphur dioxide in polar solvents have been confirmed, and it is found that the cyclic dioxides (19) formed are readily cleaved by... 

The situation would be completely different for oxycarbenium ions in a highly polar solvent such as sulphur dioxide which could compete effectively as solvating agent with the DCA and their polymers. In such systems one could envisage that both the solvent-solvated oxycarbenium ions and also the solvent-solvated teJt.-oxonium ions could coexist in a true equilibrium, and that each would react according to its own characteristics. This is an area which remains very largely unexplored, although Penczek has made a start in this direction and these considerations arose from discussions with him of his exploratory experiments with sulphur dioxide as solvent. 

Since iodine is a solid and sulphur dioxide is a gas, a polar solvent must be used for the reaction and as a dilution agent. Methanol is generally used as the solvent however, methylmonoether glycol or diethylene glycol can also be used. In these conditions, sulphur dioxide is not simply dissolved in the solvent but actually interacts with it. For example, with methanol, S02 is transformed into methylhydrogen sulphite that reacts with I2 in the presence of water. This leads to the following reaction ... 

Physical Properties.—Sulphuryl chloride is a colourless, fuming liquid, with an extremely pungent odour. Z)2 = 1-6074 ->t " = l-4437. It boils at 69-1° C. at 760 mm. pressure, and freezes at —46° C.5 The vapour density is normal at first, but when the chloride is kept, even at 100° C., its vapour commences to dissociate into sulphur dioxide and chlorine. At 200° C. dissociation is almost complete.6 When dissolved in benzene the substance shows a molecular- weight corresponding with S02C12. At ordinary temperatures the specific heat is 0-233, the latent heat of evaporation 32-4 calories per gram, and the heat of formation from the elements approximately 89,540 calories per gram-molecule.7 The dielectric constant at 20° C. is 8-5. As a solvent, the ebullioscopic constant of sulphuryl chloride has been found to have... 

Alcohol is superior to water as a solvent for sulphur dioxide, absorbing more than 200 times its own volume of the gas at 0° C. and 760 mm. 5 thus, 1 c.c. of alcohol absorbs the following volumes ... 

Liquid sulphur dioxide finds occasional use as a refrigerating liquid for the manufacture of ice and as a solvent for the extraction of fats and oils from bones and other waste animal matter. It is also employed in the refining of natural petroleum, owing to its property of dissolving aromatic and other heavy hydrocarbons which are present in petroleum distillates.1 When the distillate is shaken with liquid sulphur dioxide at a low temperature, separation into two layers occurs, one of which is the sulphur dioxide solution, the other the purified distillate containing paraffin hydrocarbons and naphthenes, which remain unaffected. 

There are several methods of manufacturing is on a commercial scale, for instance the calcination of oxalic add blended with potassium chloride, treatment of sodium chlorite with chlorine, or of sodium chlorate with sulphur dioxide in the presence of concentrated sulphuric add. Chlorine dioxide is utilized as a strong bleaching agent for cellulose, paper, flour, oils and such like, as well as a solvent for removing lignin from wood pulp. 

Reddish-yellow liquid used as a solvent and fumigant. Fumes in moist air producing sulphur dioxide, sulphur and HC1. Irritant to upper respiratory tract. Lethal to mice at 150 ppm for 1 min. 

We believe this to be the first monograph devoted to the physicochemical properties of solutions in organic solvent systems. Although there have been a number of books on the subject of non-aqueous solvents they have been devoted, almost entirely, to inorganic solvents such as liquid ammonia, liquid sulphur dioxide, etc. A variety of new solvents such as dimethylformamide, dimethylsulphoxide and propylene carbonate have become commercially available over the last twenty years. Solutions in these solvents are of technological interest in connection with novel battery systems and chemical synthesis, while studies of ion solvation and transport properties have fostered academic interest. 

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. 

Verhoef and co-workers suggested omitting the foul smelling pyridine completely and proposed a modified reagent, consisting of a methanolic solution of sulphur dioxide (0.5 M) and sodium acetate (1M) as the solvent for the analyte, and a solution of iodine (0.1 M) in methanol as the titrant the titration proceeds much faster and the end-point can be detected preferably bipoten-tiometrically (constant current of 2 pA), but also biamperometrically (AE about 100 mV) and even visually as only a little of the yellow sulphur dioxide-iodide complex S02r is formed (for the coulometric method see Section 3.5). 

In the anionotropic system of sulphur dioxide (condensed below -10° C s x 16) we are concerned with an oxidotropic solvent with self-dissociation here the 02 ion does not exist in the free state, but occurs as the solvated ion SO3. A comparable situation is found in many systems of halotropy with self-dissociation, e.g., according to the overall reactions 4.30-4.33... 

Chlorosulphonated polyethylene is obtained by reacting low density polythylene with chlorine in presence of sulphur dioxide using carbon tetrachloride as solvent. The product contains 30 per cent chlorine and 1.5 per cent sulphur. This is a sticky rubbery material and is soluble in chlorinated hydrocarbon solvents. It can be vulcanised by heating with metal oxides like litharge or magnesium oxide in presence of water. The cross-linked product is found to be resistant to chemical attack and is used in gaskets, hoses, etc. 

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