Hydrosulphids

Mercaptans (or thio-alcohols or thiols), the sulphur analogues of the alcohols, were formerly prepared by the interaction of an alkyl halide and sodium hydrosulphide in alcoholic solution ... 

Numerical Example.—Dissociation of ammonium hydrosulphide NH4IIfc NH3+HaS. 

Briceno A, Chander S (1990) Oxidation of hydrosulphide ions on gold - Part 1 A cychc voltammetry study. J Appl Electrochem 20 506-511... 

The complete reduction of nitro-compounds which contain several nitro-groups is carried out in the same way as in the case of mononitro-derivatives. If, however, only partial reduction is desired, the use of ammonium hydrosulphide is advantageous. 

Mountain BW, Seward TM (1999) The hydrosulphide/sulphide complexes of copper(I) experimental determination of stoichiometry and stability at 22°C and reassessment of high temperature data. Geochim Cosmochim Acta 63 11-29... 

It was established by Tolun and Kitchener (1963—1964) that a platinum electrode became hydrophobic when hydrosulphide ion (HS ) was oxidized at the electrode surface. A contribution to the hydrophobicity may be the production of sulphur. According to thermodynamics, the hydrolysis reaction of sodium sulphide is... 

McCarron et al. (1990) used the X-ray photoelectron spectroscopy to analyze chalcopyrite and pyrite surface after being conditioned in sodium sulphide solutions. They found that multilayer quantities of elemental sulphur were produced at the surface of both minerals in 3 x 10 and 3 x 10" mol/L sulphide solutions although for a given sulphide concentration, the surface coverage of elemental sulphur for p)uite was greater than that for chalcopyrite under open circuit conditions. Eliseev et al. (1982) concluded that elemental sulphur was responsible for the hydrophobicity of pyrite and chalcopyrite treated with sodium sulphide. Luttrell and Yoon (1984a, b) observed a shoulder due to elemental sulfixr near 164 eV in the S (2p) spectra from relatively pure chalcopyrite floated after being conditioned at different pulp potential established by different hydrosulphide concentration. 

Abstract In this chapter, the depression mechanism of five kinds of depressants is introduced respectively. The principle of depression by hydroxyl ion and hydrosulphide is explained which regulates the pH to make the given mineral float or not. And so the critical pH for certain minerals is determined. Thereafter, the depression by cyanide and hydrogen peroxide is narrated respectively which are that for cyanide the formation of metal cyanide complex results in depression of minerals while for hydrogen peroxide the decomposition of xanthate salts gives rise to the inhibitation of flotation. Lastly, the depression by the thio-organic such as polyhydroxyl and poly carboxylic xanthate is accounted for in detail including die flotation behavior, effect of pulp potential, adsorption mechanism and structure-property relation. 

Keywords depressant hydroxyl ion hydrosulphide ion cyanide hydrogen peroxide thio-organic... 

The depression by hydrosulphide ion is in a similar manner as hydroxyl depression, i.e. there is a critical pH for each HS ion concentration at a constant xanthate concentration above which no flotation is possible. In the case that the hydrophobic entity is disulphide, the mineral will be depressed when the reaction (3-5a) or (3-6a) occurs before the reaction (1-3). Thus for the pyrite /ethyl xanthate system, pyrite will be depressed if the oxidation reaction (3-5a) takes place prior to the oxidation reaction (4-35). 

Therefore, the critical pH of hydrosulphide ion depression of pyrite and galena could be calculated using Eqs. (5-15) and (5-16). The results are plotted in Fig. 5.13. The same figure is the results of contact curves reported by Wark and Cox (1933). It can be seen from Fig. 5.13 that the critical pH condition defined by electrochemical equilibrimns of Eqs. (5-15) and (5-16) is correlated reasonably well with the contact curves. The calculated concentration of sodium sulphide required for preventing the interaction between xanthate and galena or pyrite at... 

Synonyms AI3-26618 BME EINECS 200-837-3 Ethanethiol Ethyl hydrosulfide Ethyl hydrosulphide Ethyl sulfhydrate Ethyl thioalcohol FCY LPG ethyl mercap-tan 1010 Mercaptoethane 1-Mercaptoethane NSC 93877 0-2712 NSC 29026 SCC Thio-ethanol Thioethyl alcohol UN 2363... 

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. 

Thiols are prepared from alkyl halides and sodium hydrosulphide (Na+SH ) by Sn2 reaction. A large excess of Na+SH is used with unhindered alkyl halide to prevent dialkylation (R—S—R). 

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