Sulphide and cyanide

Bond et al. [68] have described a method for the simultaneous determination of down to Img L free sulphide and cyanide by ion chromatography, wifli electrochemical detection. These workers carried out considerable exploratory work on the development of ion chromatographic conditions for separating sulphide and cyanide in a basic medium (to avoid losses of toxic hydrogen cyanide and hydrogen sulphide) and on the development of a suitable amperometric detector. 

Anion Stationary phase Eluent Comments Detection LD Ref. 

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Sulphur, as sulphide ion, is detected by precipitation as black lead sulphide with lead acetate solution and acetic acid or with sodium plumbite solution (an alkaLine solution of lead acetate). Halogens are detected as the characteristic silver halides by the addition of silver nitrate solution and dilute nitric acid the interfering influence of sulphide and cyanide ions in the latter tests are discussed under the individual elements. 

Sulphur, hydrogen sulphide and metal sulphides also led either to the ignition of the sulphurous substance (S and H2S) or the incandescence of the mixture. Note that sulphides and cyanides are amongst the most dangerous salts in the presence of oxidants, a fact not to be ignored. 

These iodonium salts are usually obtained directly from arenes or organometallics and an inorganic compound of iodine (III) or (V). Once formed, iodonium salts can exchange their anion with almost any other anion exceptions are hydrosulphide, sulphide and cyanide. For large-scale preparations one of the early methods is always useful and can be applied to arenes of various kinds, including those bearing electron-withdrawing substituents. 

In order to detect these elements in organic compounds, it is necessary to convert them into ionlsable inorganie substanees so that the ionic tests of inoiganio qualitative analysis may be applied. This conversion may be accomplished by several methods, but the best procedure is to fuse the organic compound with metallio sodium (Lassalgne s test). In this way sodium cyanide, sodium sulphide and sodium halides are formed, which are readily identified. Thus ... 

Further, recommendations by suppliers for avoiding interferences must be followed, e.g., high concentrations of non-alkali metal ions, sulphide and com-plexing agents such as cyanide may be harmful. 

Hydrometallurgical methods are normally employed for recovery of gold from oxidized deposits (heap leach), low-grade sulphide ores (cyanidation, CIP, CIL) and refractory gold ores (autoclave, biological decomposition followed by cyanidation). 

Prestidge, C. A., Skinner, W. M., Ralston, J., Smart, R. S. C., 1997. Copper (II) activation and cyanide de-activation of zinc sulphide under mildly alkaline conditions. Appl. Siuf. Sci., 108 333-344... 

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 redispersion of a sol which has been precipitated by the addition of an electrolyte may also occasionally be effected by the removal of the precipitating agent through washing thus certain precipitates such as silver chloride, zinc sulphide and copper ferro-cyanide are readily redispersed in water where the precipitating salts are removed by thorough agitation and filtration. 

The chlorides, bromides, iodides, and cyanides are generally vigorously attacked by fluorine in the cold sulphides, nitrides, and phosphides are attacked in the cold or may be when warmed a little the oxides of the alkalies and alkaline earths are vigorously attacked with incandescence the other oxides usually require to be warmed. The sulphates usually require warming the nitrates generally resist attack even when warmed. The phosphates are more easily attacked than the sulphates. The carbonates of sodium, lithium, calcium, and lead are decomposed at ordinary temp, with incandescence, but potassium carbonate is not decomposed even at a dull red heat. Fluorine does not act on sodium bofate. Most of these reactions have been qualitatively studied by H. Moissan,15 and described in his monograph, Lefluor et ses composes (Paris, 1900). 

Sometimes the ore must be pretreated before it will adsorb the additive satisfactorily for example, zinc sulphide must be pretreated with dilute copper sulphate solution, which deposits copper on the ore surface by electrochemical action. Specificity of flotation may also be achieved by the addition of depressants for example, cyanide ions prevent ferrous sulphide and zinc sulphide from floating but allow... 

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