Thiosulphate ions sulphide

However, the sulphide ion can attach to itself further atoms of sulphur to give polysulphide ions, for example Sj , Sj , and so these are found in solution also. Further, the sulphite ion can add on a sulphur atom to give the thiosulphate ion, S203 which is also found in the reaction mixture. 

It shonld be pointed out here that the S—S bond in thiosulphate is easily broken. In view of the strong complexes it forms with some metal cations, the probability of a mechanism whereby the S—S bond of the complex is broken, leading to metal snlphide formation without formation of sulphide ion, should be seriously considered (see Sec. 2.5). 

It has been suggested that the thiosulphate, a reducing agent, may act as an electron donor and rednce the elemental sulphur formed in Reactions (3.21) and (3.22), forming sulphide ions ... 

The reaction of azide ion with iodine is very greatly accelerated by the presence of inorganic " -or organic sulphides, thiocyanates , thiosulphate tri-, tetra- and pentathionates and carbon disulphide . Kinetic studies are most extensive for the carbon disulphide- and thionate-catalysed reactions. 

We could not find any study of Bi(III) ions in aqueous solutions except that Wang et al. [132] obtained nanorods of bismuth sulphide by sonicating an aqueous solution of bismuth nitrate and sodium thiosulphate in the presence of complexing agents such as ethylenediamine tetraacetic acid, triethanolamine and sodium tarta-rate. Similar results were found when thioacetamide was used in place of sodium thiosulphate as a source of sulfur. However, the results improved with higher yield... 

An unusual reaction of methoxythiocarbonyl chloride with tetra-n-butylammo-nium iodide in the presence of sodium thiosulphate leads to the formation of 0,5-dimethyl dithiocarbonate [49], The reaction appears to involve a reduction step, with the iodide anion being regenerated from the released iodine by the thiosulphate ions (Scheme 4.7). In the absence of the thiosulphate ions, the thiocarbonyl chloride decomposes to yield chloromethane and carbonyl sulphide. 

Because of the strong complexes thiosulphate forms with some metal ions, it is very possible that these metal-thiosulphate complexes undergo a complex-decomposition mechanism (Section 3.3.3). However, one early study on the formation of PbS on boiling Pb and thiosulphate in water found that PbS formed more readily when excess thiosulphate was present [5], which suggests that decomposition of thiosnlphate to sulphide might be the dominant pathway under the conditions of that stndy. 

These electrons reduce elemental S formed in Reaction (3.21) or (3.22) to give sulphide (or hydrosulphide) ions, as in Reaction (3.24), which react with the metal ions. The general mechanism of sulphide generation has been assumed in most studies using thiosulphate, e.g., Nair et al [78] for SbzSs deposition and Groz-danov et al. in their study of Cu S deposition from Cu-thiosulphate solutions [76], although in this latter study it is noted that the mechanism may be more complicated in this Cu-S system. 

A sensitive colour test for sulphite ions consists in adding, drop by drop, a 0-01 per cent, solution of Fast Blue R crystals, shaking after each addition, until the violet coloration disappears and a yellow solution is produced the test is sensitive to one part of sulphurous acid in about 175,000. Thiosulphates and polythionates do not interfere, but sulphides and hydroxides must be absent.1... 

Reducing agents (sulphides, thiosulphates, etc.) interfere since they yield molybdenum blue hexacyanoferrate(II) ions give a red colouration. Arsenates (warming is usually required), arsenites, chromates, oxalates, tartrates, and silicates give a similar reaction with some variation in the colour of the precipitate. All should be removed before applying the test. 

It is possible that Gottschalk and Buehler (1912) carried out the oxidation with an excess of oxygen which would not occur in nature at the oxidation interface of a mineral deposit. Granger and Warren (1969) conducted experiments to investigate the oxidation of iron sulphides by an aerobic aqueous phase in a sterile system. The objective was to study the formation of unstable intermediate ions during the oxidation process. The intermediate sulphur species detected were sulphite and thiosulphate. In general these products are more easily oxidised than the metallic sulphides and are stable only if removed from the oxidising environment. 

The bleaching of Methylene Blue by 8203 affords a sensitive method for determination of thiosulphate [70]. It is possible to determine thiosulphate after extraction of its ion-associates with some basic dyes, e.g., Rhodamine B, Rhodamine 6G, or Crystal Violet [71]. Thiosulphate present in concentrations of the order of 10 M have been determined after the oxidation with iodine by measuring the absorbance due to I3 [72]. Thiosulphate can also be determined in an indirect reaction, in which 8203 reacts with Hg(II) thiocyanate to release SCN which gives a colour reaction with Fe(III) [73]. A method for simultaneous determination of thiosulphate, sulphite, and sulphide has been proposed [74]. 

Collect the reaction solutions containing mercury ions which remain following completion of the manganese determination. Per 500 ml of solution treat with 30 g of sodium thiosulphate and then with 300 ml of 30 % sodium hydroxide solution. In this process the mercury is removed from the solution as sulphide. Hg2+ ions are no longer detectable in the filtrate of the supernatant colourless liquid (flameless atomic-absorption spectrophotometry detection limit 0.001 mg/1). 

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