Sulphide ions reactions

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. 

Consequently they cannot be prepared by the addition of sulphide ions to a solution of the metal salt, the hydrated metal ions being so strongly acidic that the following reaction occurs, for example... 

The reactions of aqueous solutions of nickel(II) salts with hydroxide ions, with excess ammonia, with sulphide ion and with dimethyl-glyoxime (see above) all provide useful tests for nickel(II) ions. 

The reaction of Cd (aq) with sulphide ion, to give yellow CdS, and with hydroxide ion to give the white CdfOHlj, soluble in ammonia, provide two useful tests. 

Figure 4.13 A solid-state electrode showing a third-order response. An alternative modification to the electrode described in Figure 4.11 will permit the measurement of cadmium ions in solution. The membrane is composed of a mixture of silver and cadmium sulphides. The surface reaction between the cadmium ions in the test solution and the sulphide ions in the membrane will affect the equilibrium between the sulphide ions and the silver ions in the membrane.

SWV has been applied to study electrode reactions of miscellaneous species capable to form insoluble salts with the mercury electrode such as iodide [141,142], dimethoate pesticide [143], sulphide [133,144], arsenic [145,146], cysteine [134, 147,148], glutathione [149], ferron (7-iodo-8-hydroxyquinolin-5-sulphonic acid) [150], 6-propyl-2-thiouracil (PTU) [136], 5-fluorouracil (FU) [151], 5-azauracil (AU) [138], 2-thiouracil (TU) [138], xanthine and xanthosine [152], and seleninm (IV) [153]. Verification of the theory has been performed by experiments at a mercury electrode with sulphide ions [133] and TU [138] for the simple first-order reaction, cystine [134] and AU [138] for the second-order reaction, FU for the first-order reaction with adsorption of the ligand [151], and PTU for the second-order reaction with adsorption of the ligand [137]. Figure 2.90 shows typical cathodic stripping voltammograms of TU and PTU on a mercuiy electrode. The order of the... 

Generation of aryl radicals by reduction of aryl halides in the presence of some nucleophiles, particularly alkyl or aryl sulphide ions and cyanide ions, leads to bond formation with the generation of a new radical-anion. Overall, a reaction between the initial aryl halide and a nucleophile is triggered at the cathode and is an equivalent of the Sr I process. It proceeds in stages according to Scheme 4.6 [156] and requires only a catalytic concentration of radical-anion. The reaction can... 

The CdS forms through a number of different possible pathways simple ionic reaction between Cd and sulphide ion topotactic conversion of Cd(OH)2, which may be present in the deposition solution, to CdS by sulphide and decomposition of a complex between Cd (whether as a free ion or as a Cd compound. 

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 initial nucleation stage of the complex-decomposition mechanism is probably similar to the simple free-anion mechanism. Either ionic or molecular metal species (ion-by-ion) or Cd(OH)2 (cluster) adsorbs on the substrate. However, instead of conversion of the hydroxide to sulphide by topotactic reaction with sulphide ions, the chalcogenide precursor (in almost all studies of this mechanism, that is thiourea) adsorbs on the Cd(OH)2 surface to form a hydroxide-thiourea complex, which then decomposes to CdS. 

Considering that homogeneous precipitation of metal chalcogenides (mainly sulphides) by reaction between metal ions and dissolved chalcogen is well established, the main difference between this deposition and similar reactions seems to be that the products adhere to a substrate to give a visible fdm (in this case) rather than only precipitate. Whether this is connected with the redissolu-tion/redeposition process that occurs with the Sn-S system or has some other explanation is important. If the former, it may be limited to only those systems that behave similarly. Otherwise it is not unreasonable to expect that other metal sulphides and selenides (possibly also tellurides, although tellurium tends to be much less soluble, if at all, in such solvents) may be deposited as films in this manner. 

Funazo et al. [812] have described a method for the determination of cyanide in water in which the cyanide ion is converted into benzonitrile by reaction with aniline, sodium nitrite and cupric sulphate. The benzonitrile is extracted into chloroform and determined by gas chromatography with a flame ionisation detector. The detection limit for potassium cyanide is 3 mg L 1. Lead, zinc and sulphide ion interfere at lOOmg L 1 but not at lOmgL-1. 

The products of anode- and cathode reaction - sulphide ions and hydroxyl ions respectively are accumulated in their half-cells and induced concentrative electromotive force hindering MH charging. However, MH charging reaction is possible. We also tried to determine MH materials that are the most appropriate for this application. 

Hydrogen sulphide (cf. reaction 3) and sulphur dioxide gas reduce iron(III) ions also ... 

The earliest studies showed no evidence for intermediates in the reactions of carbonoxysulphide and of carbon disulphide with hydroxide ion (for which the stable products are carbonate, trithiocarbonate and sulphide). Wronski followed the rates of formation of sulphide ion (1) and of trithiocarbonate (2), viz. 

Other work dealing with this reaction includes a study of the exchange reaction in fused alkali nitrate solutions and an examination of the effect of sulphide ion on catalysis by vanadium(V) and molybdenum(VI) . Another group of experimental investigations of the iodate-iodide reaction has been primarily concerned with the Landolt reaction (p. 388). These are satisfactorily interpreted in terms of Dushman s original rate expression. 

Many methods for sulphide and H2S are based on the reducing properties of S(-II). Hydrogen sulphide reduces molybdate in acid medium to molybdenum blue, and the molybdophosphate to phosphomolybdenum blue [52]. Iron(III) reduced by H2S in the presence of 1,10-phenanthroline gives the orange Fe(phen)3 complex [2,53], Hydrogen sulphide may be determined after conversion into thiocyanate by the reaction with Fe(III) [54]. Sulphide has been determined also by a colour redox reaction with nitroprusside [55-57], In another sensitive reaction the sulphide ions decompose the Ag complex with Cadion 2B and Triton X-100 (e = 2.5-10 ) [58], In another indirect method sulphide releases the chloranilate ion from the Hg(Il) chloranilate [59]. Sulphide has also been determined by a method based on its reaction with bromate, followed by bromination of 2 ,7 -dichlorofluorescein by the bromine released [60]. 

In order to minimize the hydrogen evolution corrosion reaction that occurs at the open circuit potential and on the charge, which lowers the energy and ciurent efficiency, electrolyte additives are used in order to increase the hydrogen overpotential. In particular, sulphide ions have favourable effects. 

The reaction of vinylacetylene with sodium sulphide and sodium hydrosulphide in DMSO-sodium or potassium hydroxide and water has been studied in detail. The products formed were (17), (18), and (19). Conditions for selectively obtaining (17) or (19) have been worked out, while (18) was only formed in 25% yield. Interestingly, thiophen is the main product from the reaction of vinylacetylene with sulphide ions generated from elemental sulphur. The formation of thiophen appears not to be caused by oxidation of (19) by elemental sulphur. ... 

Many sulphur compounds can be assayed without prior combustion owing to certain subtle properties of organic sulphur bonds [409—415]. Thus, thiourea [410] can be assayed directly in sodium hydroxide media with a sulphide ion-selective electrode. The assay is supported by reactions (24) and (25) ... 

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