Cupric sulphide

In the actual flotation system, the activators on the sphalerite surface are some copper sulphide compounds containing different amounts of copper, namely some non-chemometric cupric sulphide. Based on the electrochemical theory of chalcocite in geologically minerogenic process, they may be chalcocite (CU2S), diulerite(Cui.96S), Cui,7i i.g2S, anilite(Cui.75S), geerite(Cui.6oS), spionkopite (CU1.40S), Cul.l2S and covellite (CuS). 

Many of the heavier thiosulphates when heated with water give rise to the corresponding sulphides. 3 To this ready decomposition of the thiosulphate is due the precipitation of sulphides when hot acid-containing solutions of various metals are treated with sodium thiosulphate solution.8 When a solution of alkali thiosulphate is boiled with a copper salt, the yellow precipitate of sodium cuprous thiosulphate first formed undergoes decomposition to produce cuprous and cupric sulphides and free sulphur, the relative amounts of these products depending on the thiosulphate concentration, the duration of boiling, and the acidity of the solution.4... 

Fig. 4.26 Discharge curve of a lithium-cupric sulphide pacemaker cell al 37°C under a load of 12.3 kfi. (By permission of the Electrochemical Society A.J, Cuesta and D.D. Bump, Proceedings of the symposia on power sources for biomedical implantable applications and ambient temperature lithium batteries, eds B.B. Owens and N. Margalil, 1980. p. 95.)...

Batteries based on cupric sulphide cells (three in series) were originally developed and used with cardiac pacemakers. Reduction of CuS takes place in two stages ... 

When suspended in a solution containing both ammonia and ammonium (or other) salts, air at atmospheric pressure oxidizes cuprous sulphide to cupric sulphate and thiosulphate, the reaction being slower than with cupric sulphide. In suspension in neutral or acidic solutions, cupric sulphate is produced, the reaction being less energetic than in presence of ammonia, and up to 160° C. requiring compressed air.3... 

Cupric sulphide, CuS.—By adopting special experimental precautions, it is possible to prepare cupric sulphide free from cuprous sulphide and sulphur by precipitating a solution of cupric sulphate or chloride with hydrogen sulphide,8 although if no precautions are taken the precipitate is likely to be contaminated with these substances.9 At 180° C. concentrated sulphuric acid converts copper into a mixture of cupric sulphide and sulphur, from which the sulphur can be removed by heating at 160° C. in a rapid current of hydrogen.10... 

A crystalline variety of cupric sulphide is produced by heating cupric sulphate with ammonium thiocyanate above 180° C.11 The amorphous form can also be rendered crystalline by heating in a sealed tube with ammonium hydrogen sulphide at 150° to 200° C., the product consisting of lustrous, violet, hexagonal leaflets.12... 

Cupric sulphide occurs in nature as covellite or indigo-copper, indigo-blue, hexagonal plates, density 4-59 to 4-64, and hardness 1-5 to 2.13 The dark-green, amorphous variety has the density 4-16,14 and is a good cbnductor of electricity.15 It is decomposed in vacuum at 400° C. into cuprous sulphide and sulphur.16 Its oxidation by air in ammoniaeal, neutral, and acidic suspensions is similar to that of cuprous sulphide... 

In qualitative analysis copper is detected by precipitation as cupric sulphide from hydrochloric-acid solutions of its salts. To prevent the formation of a colloidal precipitate, the solution should be hot, and should contain excess of the acid. The sulphide is soluble in hot, dilute nitric acid, and in potassium-cyanide solution, but almost insoluble in solutions of alkali-metal sulphides. It dissolves to some extent in ammonium-sulphide solution. Other aids in the detection of copper are the blue colour of solutions of cupric-ammonia salts the reddish-brown precipitate of cupric ferrocyanide, produced by addition of potassium ferro-cyanide to cupric solutions the formation of an intense purple coloration by the interaction of hydrogen bromide and cupric salts, a very delicate reaction2 the formation of a bluish-green borax bead and the ready isolation of the metal from its compounds by the action of reducers. 

It is also reduced to metallic gold by phosphorous acid and sodium hypophosphite, and by cupric sulphide in accordance with the equation10... 

Cuprous ferric sulphide, Cu2S.FeaS3, occurs in nature as copper pyrites, cholcopyrite, or towcmite, and is one of the commonest ores of copper (see p. 23). It is tetragonal, possessed of a brass-yellow colour, and exhibits a conchoidal fracture. It is decomposed by nitric acid, and tarnishes upon exposure to air, frequently yielding beautiful iridescent surfaces, a blue colour predominating. Masses of such tarnished ore are found in Cornwall, and arc known as peacock ore. The blue colour is probably due to the formation of a surface layer of cupric sulphide or covellite, CuS. 

Haltner and Oliver found that several metallic sulphides brought about an improvement in the load-carrying capacity when mixed with molybdenum disulphide. The sulphides included stannic and stannous sulphides, lead sulphide, ferrous suiphide and cuprous and cupric sulphides, and in a standard test procedure there was up to a ten-fold increase in load-carrying capacity. They speculated that the action of the added sulphides was similar to that of extreme-pressure additives in liquid lubricants. This would imply the formation of some protective film on the substrate surface. Pardee later suggested that the effective mechanism was more likely to be oxidation inhibition. An alternative would seem to be the possibility that certain sulphides can act as an additional source of sulphur to form sulphide on the substrate surface, and thus improve adhesion of the molybdenum disulphide, as discussed in the previous chapter. 

Note the abnormal distances in MnS2, attributed to the stability of the half-filled 3d shell. A cupric sulphide with the composition CuSj.g having the pyrites structure has been prepared from covellite (CuS) and S under high pressure at a temperature of 350°C or above. ... 

Hydrated antimony pentoxide Hydrated manganese dioxide Anhydrous manganese dioxide Acidic aluminium oxide Tin dioxide Zirconium phosphate Cupric sulphide Cuprous chloride Cerous oxalate Anion exchange resin Cation exchange resin... 

---