Sulfur sulfide ions

In type A reaction soluble sulfide ions combine with metal ions to form a precipitate of insoluble metal sulfide. Sulfur s oxidation state of minus two does not change in this reaction. The reaction is... 

These reactions show sulfur in the role of an oxidizing agent. The properties of compounds such as ZnS suggest they contain the sulfide ion, S-2. The formation of this ion again can be expected on the basis of the fact that the neutral sulfur atom has two electrons less than enough to fill the valence orbitals. Acquisition of two electrons completely fills the low energy valence orbitals and solid ionic compounds can be formed. 

An alternative procedure for removing an ion from solution is to change its identity by changing its oxidation state. The metal ions in very insoluble heavy metal sulfide precipitates can be dissolved by oxidizing the sulfide ion to elemental sulfur. For example, copper(II) sulfide, CuS, takes part in the equilibrium... 

However, when nitric acid is added, the sulfide ions are oxidized to elemental sulfur ... 

Sulfur-containing compounds [1-3] e.g. thiols [4, 5] and thioethers [5] sulfide ions [4] thiourea derivatives... 

The various oxidation states of sulfur have been determined by polarography. The electrochemical oxidation of sulfide ions in aqueous solution may lead to the production of elementary sulfur, polysulfides, sulfate, dithionate, and thiosulfate, depending on the experimental conditions. Disulfides, sulfoxides, and sulfones are typical polarographically active organic compounds. It is also found that thiols (mer-captans), thioureas, and thiobarbiturates facilitate oxidation of Hg resulting thus in anodic waves. 

Changing the substrate from gold to silver has been shown to strongly affect the structure of the first few layers of CdS grown by ECALE. STM measurements carried out on the first CdS layer on Ag(lll) revealed a much less compact structure than the one found on Au(lll). This disparity was tentatively attributed to the different structure of the first S layer on Ag(l 11), as obtained by oxidative UPD from sulfide ion solutions, due to a higher affinity of sulfur for silver than for gold. The Cd layers were attained on S by reductive UPD from cadmium ion solutions. Precursors for both elements were dissolved in pyrophosphate/NaOH at pH 12 [43 5],... 

Fig. 4.9 Schematic illustration of the electrosynthesis procedure using a sulfur-modified gold electrode and alternating exposure to indium- and sulfide ion containing aqueous baths, (a) A polycrystalline gold surface is first modified with a sulfur layer, (b) Indium is plated onto this layer forming indium sulfide, (c) Indium continues to deposit atop the indium sulfide layer, (d) Transfer back to a sulfide ion containing bath results in the suMdization of the residual indium sites. (Reprinted from [95], Copyright 2009, with permission from Elsevier)...

Potentiometric titration with a sulfide ion-selective electrode as an indicator has been used to measure hydrogen sulfide in the air at ppb levels (Ehman 1976). The method has been shown to have very good accuracy and precision. No interference could be found from nitrogen dioxide, sulfur dioxide, or ozone. 

Sulfide ions in solution react with sulfur to produce polyatomic anions known as the polysulfides. When... 

Catalytic activity in presence of sulfide ion (expressed as percent of activity under sulfur free conditions) none 21 59 67... 

D—The dichromate ion oxidizes the sulfide ion to elemental sulfur, as the sulfide ion reduces the dichromate ion to the chromium(III) ion. Chromium goes from +6 to +3,while sulfur goes from -2 to 0. The hydrogen remains at +1, so it is neither oxidized nor reduced. 

While the pH of blood must be maintained within strict limits, the pH of urine can vary. The sulfur in foods, such as eggs, is oxidized in the body and excreted in the urine. Does the presence of sulfide ions in urine tend to increase or decrease the pH Explain. 

The first reaction is p-elimination in cysteine, serine, phosphoserine, and threonine residues due to attack by hydroxide ion, leading to the formation of very reactive dehydroalanine (DHA). In a cystine residue, this results in rupturing of the disulfide bond and liberation of a sulfide ion and free sulfur (Figure 13.4). Nucleophilic additions of the s-amino group of the protein-bound lysine to the double bond of DHA residue causes crosslinking of the polypeptide chain. After hydrolysis, a mixture of L-lysino-L-alanine and L-lysino-D-alanine, with probably a small proportion of dl and dd isomers,... 

Obviously, the donor activity of the nucleophile, that is, the sulfide ion is enhanced as the negative charge is dispersed along the polysulfide ion produced from the sulfide on the addition of elemental sulfur. This increases the mobility of electrons and facilitates electron transfer. That is why this reaction can be initiated in such a simple way as the addition of elemental sulfur. 

First, consider the effect of pH-increase due to the reaction of an acidic fluid with a carbonate-bearing host rocks. At pH = 5, practically all of the dissolved sulfur is undissociated H2S, whereas at pH = 9 the dissolved sulfide is almost entirely dissociated. Since H2S concentrates " S relative to dissolved sulfide ion, an increase in pH leads directly to an increase in the 5 " S of precipitated sulfides. 

Iron-sulfur clusters (7) occur as prosthetic groups in oxidoreductases, but they are also found in lyases—e.g., aconitase (see p. 136) and other enzymes. Iron-sulfur clusters consist of 2-4 iron ions that are coordinated with cysteine residues of the protein (-SR) and with anorganic sulfide ions (S). Structures of this type are only stable in the interior of proteins. Depending on the number of iron and sulfide ions, distinctions are made between [Fe2S2], [Fe3S4], and [Fe4S4] clusters. These structures are particularly numerous in the respiratory chain (see p. 140), and they are found in all complexes except complex IV. 

Ions Containing Sulfur Sulfate Ion Sulfide Ion Ions with Nitrogen... 

The electrochemical behavior of sulfur, sulfide (H8 , S ) and polysulfide ions in water is much less documented than for nonaqueous solvents. Experimental studies are less numerous and do not include a systematic study versus the stoichiometry n of polysulfides M28 . The conclusions of these investigations are often speculative, since the experimental curves do not display strong evidence for chemical species involved in the proposed mechanisms. Moreover, the very low solubility of sulfur in water does not allow the study of its electrochemical reduction in water. 

To allow the growth of another semiconducting material having the sulfide ion as the anion component, for example, CdS. The SILAR process has been proposed. For InP (n), the mechanism of sulfurization (the first step of CdS deposition) has been described [104] reversible adsorption of HS ions, followed by the irreversible expulsion of... 

Sulfurization can be performed by simple dipping or under applied (anodic) bias. For GaAs, the anodization of this material in the presence of (NH4)2S [105-108] leads to the formation of Ga(II+)S(—II), GaS, which implies redox reactions between Ga + ions issued from the material and sulfide ions. 

The zinc blende structure can be described as a ccp array of sulfide ions with zinc ions occupying every other tetrahedral hole in an ordered manner. Each zinc ion is thus tetrahedrally coordinated by four sulfides and vice versa. Compounds adopting this structure include the copper halides and Zn, Cd, and Hg sulfides. Notice that if all the atoms were identical, the structure would be the same as that of a diamond (see Section 1.6.5). Notice that the atomic positions are equivalent, and we could equally well generate the structure by swapping the zinc and sulfurs. 

The sulfide ion is probably present as polysulfides, for example, S3- (Section 3.4), in the molten sulfur solvent. The anode and cathode compartments are separated by a refractory fast ion conductor through which Na+... 

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