Cobalt precipitation

Arsenic and lead are conveniently co-precipitated and removed with the cobalt precipitate. Finally, copper is separated from solution as copper(II) sulfide by stirring in nickel powder and elemental sulfur... 

After filtration, addition of sodium sulphide to the clear solution effects the precipitation of the three metals, cobalt, nickel, and manganese, as sulphides. Digestion with the calculated quantity of ferric chloride oxidises the manganese sulphide to sulphate, which passes into solution. The residue consists of cobalt and nickel sulphides, which are washed and converted into their soluble sulphates by roasting. The sulphates are extracted with water, and converted into chlorides by addition of calcium chloride solution. Their separation is effected g.s follows The requisite fraction of the chloride solution is precipitated with milk of lime, and the insoluble hydroxides of nickel and cobalt thus obtained are oxidised to the black hydroxides by treatment with chlorine. The. washed precipitate is then introduced into the remainder of the chloride solution, and the whole is well stirred and heated, when the black hydrated oxide of nickel passes, into solution, displacing tlm Remainder of. the cobalt from the solution, into. the precipitate.. The final product is thus a suspension of hydrated peroxide.of cobalt,in p. solution of nickel chloride, from which idle cobalt precipitate is removed by filtration, washed, and ignited, to the black oxide. 

Manganese salts Traces of nickel and cobalt precipitated with a sulfide precipitation accelerated when activated carbon is present. 

Cobalt precipitation catalysts. The development of cobalt catalysts (Fischer and Koch, 12) was similar to the development of the corresponding nickel catalysts. In the case of cobalt, however, it was easier to prevent extensive methane formation. The lOOCo 18Th02 100 kieselguhr catalyst became the so-called standard cobalt catalyst. 

If the Mn/(Mn+Co) ratio is not too high in the cobalt bleed from the main Cu hydrometallurgical circuit, it is possible to have a fairly good selective cobalt precipitation as hydroxide or basic sulphate after acid neutralisation, iron and copper removal [16]. This is due to the difference of solubility products of cobalt and manganese hydroxides with pS values for Co, and Mn hydroxides of respectively 15.4, and 12.7 (pS = -log [solubility product]). The cobalt precipitation will be done at a pH around 8.2, with close to 98% cobalt precipitation and 5-20% manganese co-precipitation. An even better selectivity can be reached by doing the precipitation in two steps counter-currently. This is probably, in most cases, the easiest and cheapest way to remove Mn from Co solutions. 

If the compound contains an active cobalt-containing adhesion promoter, metallic cobalt precipitates onto the brass surface and also forms the Me-S bond, in addition to copper. Zinc can also form this bond, but does not bond to rubber, as the zinc sulphide growth rate is low (see stage IV). The role of cobalt in NR skim stocks is thus to activate (or... 

CoAsS, are also used as sources. The ore is roasted and Co is precipitated as the hydroxide and then reduced to Co with carbon (hep below 417 - C, cep to m.p.). The metal is silvery white and readily polished. It dissolves in dilute acids and is slowly oxidized in air. Adsorbs hydrogen strongly. The main use of cobalt is in alloys. Cobalt compounds are used in paints and varnishes, catalysts. Cobalt is an essential element in the diet. World production 1976 32 000 tonnes metal. 

Aqueous ammonia can also behave as a weak base giving hydroxide ions in solution. However, addition of aqueous ammonia to a solution of a cation which normally forms an insoluble hydroxide may not always precipitate the latter, because (a) the ammonia may form a complex ammine with the cation and (b) because the concentration of hydroxide ions available in aqueous ammonia may be insufficient to exceed the solubility product of the cation hydroxide. Effects (a) and (b) may operate simultaneously. The hydroxyl ion concentration of aqueous ammonia can be further reduced by the addition of ammonium chloride hence this mixture can be used to precipitate the hydroxides of, for example, aluminium and chrom-ium(III) but not nickel(II) or cobalt(II). 

These are practically insoluble in water, are not hydrolysed and so may be prepared by addition of a sufficient concentration of sulphide ion to exceed the solubility product of the particular sulphide. Some sulphides, for example those of lead(II), copper(II) and silver(I), have low solubility products and are precipitated by the small concentration of sulphide ions produced by passing hydrogen sulphide through an acid solution of the metal salts others for example those of zincfll), iron(II), nickel(II) and cobalt(II) are only precipitated when sulphide ions are available in reasonable concentrations, as they are when hydrogen sulphide is passed into an alkaline solution. 

Cobaltilll) oxide is obtained as a brown precipitate Co Oj.aq when cobalt(II) hydroxide is oxidised in alkaline conditions (or when a cobalt(III) is decomposed by aqueous alkali). On heating it gives the black mixed oxide C03O4. 

Cobaltill) hydroxide is obtained as a precipitate when hydroxide ion is added to a solution containing cobalt(II) ions. The precipitate is often blue, but becomes pink on standing it dissolves in excess alkali to give the blue [CofOH) ion, and in slightly alkaline solution is easily oxidis by air to a brown solid of corttposition Co "0(OH). 

Cobalt U) sulphide is precipitated as a black solid by addition of sulphide ion to a solution of a cobalt(II) salt, in alkaline solution. 

For a cobalt(ll) salt, the precipitation of the blue->pitik cobalt(II) hydroxide by alkali, or precipitation of black cobalt(II) sulphide by hydrogen sulphide provide useful tests the hydroxide is soluble in excess alkali and is oxidised by air to the brown CoO(OH) . 

Addition of excess potassium nitrite acidified with ethanoic acid gives a precipitate of the potassium hexanitro-cobaltate(lll), K3[Co(N02)6] (P. 403). 

Decomposition of most cobalt(III) complexes by boiling with alkali gives a brown precipitate of the hydrated oxide C02O3. aq (p.402). This will quantitatively oxidise iodide to iodine. 

When cobalt(II) chloride was dissolved in water, a pink solution A was formed. The addition of concentrated hydrochloric acid to A gave a blue solution B. If solution A was treated with concentrated ammonia solution a blue-green precipitate was formed upon addition of further ammonia solution followed by the passage of air through the mixture, an orange-red solution C was produced. 

A compound of cobalt has the formula Co(NH3)jtCl. 0.500 g of it was dissolved in 50.00 cm M hydrochloric acid the excess acid required 40.00 cm M sodium hydroxide solution to neutralise it. Another 0.500 g portion of the compound was dissolved in water and allowed to react with excess silver nitrate solution. 0.575 g of silver chloride was precipitated. 

Hydantoin itself can be detected ia small concentrations ia the presence of other NH-containing compounds by paper chromatography followed by detection with a mercury acetate—diphenylcarba2one spray reagent. A variety of analytical reactions has been developed for 5,5-disubstituted hydantoias, due to their medicinal iaterest. These reactions are best exemplified by reference to the assays used for 5,5-diphenylhydantoiQ (73—78), most of which are based on their cycHc ureide stmcture. Identity tests iaclude the foUowiag (/) the Zwikker reaction, consisting of the formation of a colored complex on treatment with cobalt(II) salts ia the presence of an amine (2) formation of colored copper complexes and (3) precipitation on addition of silver(I) species, due to formation of iasoluble salts at N. ... 

Nickel and cobalt are recovered by processes that employ both pressure leaching and precipitation steps. The raw materials for these processes can be sulfide concentrates, matte, arsenide concentrates, and precipitated sulfides. Typically, acidic conditions are used for leaching however, ammonia is also effective in leach solutions because of the tendency for soluble cobalt and nickel ammines to form under the leach conditions. 

Vanadium—Cobalt-Iron Alloys. V—Co—Fe permanent-magnet alloys also are ductile. A common commercial ahoy, Vicahoy I, has a nominal composition 10 wt % V, 52 wt % Co, and 38 wt % Fe (Table 10). Hard magnetic properties are developed by quenching from 1200°C for conversion to bcc a-phase foUowed by aging at 600°C (precipitation of fee y-phase). The resulting properties are isotropic, with ca kJ/m ... 

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