Sulphites, organic

The presence of sulphur may indicate a sulphate of an organic base, alkyl sulphate, sulphite, sulphide, incrcaptan, sulphonit and, bisulphite unnpound of aldehyde or ketone. 

With the salts of certain weak acids, such as carbonic, sulphurous, and nitrous acids, an additional factor contributing to the increased solubility is the actual disappearance of the acid from solution either spontaneously, or on gentle warming. An explanation is thus provided for the well-known solubility of the sparingly soluble sulphites, carbonates, oxalates, phosphates(V), arsenites(III), arsenates(V), cyanides (with the exception of silver cyanide, which is actually a salt of the strong acid H[Ag(CN)2]), fluorides, acetates, and salts of other organic acids in strong acids. 

A solution of mcpba (11.5 mmol) in dichloromethane (30 ml) was added to a stirred solution of the vinylsilane (10 mmol) in dichloromethane (50 ml) at 0°C. After stirring for 1 h, the mixture was washed with aqueous sodium hydrogen sulphite (50 ml), saturated sodium hydrogen carbonate solution and brine. The organic solution was then dried and concentrated, prior to purification by distillation or chromatography. 

Salmonella typhi, in the presence of glucose, reduces bismuth sulphite to bismuth sulphide, a black compound the organism can produce hydrogen sulphide from sulphur-containing amino acids in the medium and this will react with ferrous ions to give a black deposit of ferrous sulphide (Table 1.2). 

The crade product, suspended in 100 mL of diethyl ether is treated with a solution of sodium sulphite (21 g, 170 mmol) and potassium carbonate (16 g, 161 mmol) in 250 mL of water in a 500 mL separatory funnel. The mixture is shaken until aU the solid has disappeared, the ether layer is separated, the aqueous layer is extracted with ether and the combined organic phase is washed with water, dried (Na2S04) and evaporated (aspiration vacuum) giving the yellowish oil of pure tellurophene 3.3 g (59%), b.p. 102°C/350 torr (partial dec.). 

In 1862, E. C. C. Stanford proposed the carbonization of the drift-weed in closed retorts so as to recover tar and ammoniacal liquor in suitable condensers. This modification did not flourish because of the subsequent difficulties in extracting soluble iodides from the charcoal. V. Vincent (1916) claims that soln. containing aluminium sulphate extract the alkali iodides from seaweed leaving behind the organic matter which prevents the direct precipitation of iodine or iodides. The alkali iodide soln. is treated with copper sulphate for cuprous iodide, or by soln. of sulphites for iodine. M. Paraf and J. A. Wanklyn proposed to heat the drift-weed first with alkali hydroxide so as to form oxalic and acetic acids, which could be crystallized from the lixivium. The economical treatment of seaweed for iodine has been discussed by A. Puge. 

It may appear on first consideration that neutral sulphite of lime, which is very little soluble in water, could have but little effect on the chlorine combined with the fibre but the fact that hydrochloric acid dissolves ueutral sulphite of lime with formation of soluble bisulphite of lime, will readily explain its action. Now hydrochloric acid is invariably gaueratad. whenever ohlorine gas acts as a decoloring agent on organic substances. 

The Sulphites.—Sulphurous acid gives rise to normal sulphites of the type M2S03 and acid salts of the type MHS03, where M represents a univalent metal atom. The normal salts are odourless and do not resemble the free acid or sulphur dioxide in their very harmful effect on living organisms. On the other hand, the acid sulphites readily yield sulphur dioxide they have an acid reaction towards phenolphthalein, but are neutral towards methyl orange. 

When an alkali sulphite is allowed to react with the bromide or iodide of an organic radical, for example with ethyl iodide, the resulting compound, ethylsulphonic acid, undoubtedly possesses the unsym-0. OH... 

On the other hand, much stronger evidence is available in favour of the earlier formula,4 which accords well with the relationship between the acid and the polythionic acids.5 The formation of sodium thiosulphate by Spring s synthesis from sodium sulphide and sodium sulphite (p. 194) is definitely favourable to this constitution, as also especially is the fact that an alkali thiosulphate will react with only an equimoleeular proportion of an organic (alkyl) halide,6 the product... 

Estimation of Selenium in Organic Compounds.—A trustworthy method consists in oxidising the substance with fuming nitric acid, refluxing with concentrated hydrochloric acid until the nitrous fumes disappear and then precipitating the selenium with sodium sulphite.7... 

The detection and estimation of selenium in the mother-liquors from the preparation of sulphite-cellulose is rendered difficult by the colour of these liquors, due to the organic substances present. The presence of the element is indicated by the fact that a red deposit is formed on the sides of the combustion tube when the organic matter is being burnt off. Estimation may be carried out by evaporating the liquor until all the free sulphur dioxide has been evolved, acidifying with hydrochloric acid and boiling to remove the last traces of sulphur dioxide. After allowing to stand in a warm place for a few days the selenium settles to the bottom of the container and may be estimated as described.4... 

The microbiocidal effect increases as the pH falls below 4.0, and because of this S02 is ideally suited for most soft drink formulations. However, its preserving action is impaired by a tendency to react with many of the fruit components of soft drinks to form organic sulphites, in which state the S02 is said to be bound . Although the preservative properties are due mainly to free S02, it is necessary to analyse for total S02 (i.e. free plus bound) as legislation for safe levels refers only to maximum total concentrations. 

Note. (1) In an alternative procedure,11 iodine (3.8 g, 15 mmol) is dissolved in benzene (50 ml), to this solution is added a mixture of anhydrous aluminium chloride (4.0 g, 30 mmol) and copper(n) chloride (4.0 g, 30 mmol) previously dried at 120°C/3mmHg for more than 3 hours. The mixture is stirred at 40 °C for 2 hours, and then poured into water. The organic layer is washed with aqueous sodium hydrogen sulphite, dried and fractionally distilled. The yield of iodobenzene is 79 per cent. 

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