Cobalt

“ The name cobalt is given at present to that metal and its ores, the oxides of which are largely employed in the manufactures of glass, porcelain and pottery, for the production of a blue colour. The cobalt ores are first roasted and freed from foreign mineral bodies, particularly sulphur, iron, nickel, bismuth, and arsenic, with which they are united, and then well calcined, and sold, either mixed or unmixed with fine sand, under the name of zaffer (zaffera) ”

“ The use of cobalt does not imply a knowledge of its metal; for the moderns made brass and smalt for whole centuries, before they learned to prepare zinc and regulus of cobalt.
It seems, however, difficult to answer this question; for one can scarcely hope to discover cobalt with any certainty among those minerals mentioned by the ancients. They could describe minerals in no other manner than according to their exterior appearance, the country where they were found, or the use to which they applied them. ”

“ Metallic cobalt may be obtained by reduction of the oxide or chloride in a current of hydrogen at a red heat, or by heating the oxalate, under a layer of powdered glass. As prepared by the reduction of the oxide it is a grey powder. In the massive state it has a colour resembling polished iron, and is malleable and very tough. ”

“ With ammonia the oxides of cobalt form a series of compound bases, which give rise to salts of great interest and complexity; these may be regarded as ammonium salts, in which part of the hydrogen is replaced by ammonium and another part by cobalt in various conditions of atomicity corresponding to the oxides. The alloys of cobalt are not of much importance. It combines most readily with arsenic or antimony, forming the highly crystalline compounds known by the general name of speiss, which can scarcely be considered as alloys. ”

“ It is only when cobalt is present that any further separation is required. Cobalt hydrate takes up oxygen from the air, and on adding potassium cyanide some may refuse to dissolve; and the solution itself acquires a brown colour, which becomes deeper on standing. At this stage the cobalt is easily separated. The solution containing the nickel and cobalt with no great excess of acid, is made alkaline by adding 20 c.c. of soda exactly as in preparing for a titration. So, too, the solution of cyanide is added so as to have an excess of 20 or 30 c.c. ”

“ The oxide of cobalt combines, with strong heat in the oxidation flame, with various earths and infusible metallic oxides, and thus produces peculiarly colored compounds, and is therefore used for their detection; (alumina, magnesia, oxide of zinc, oxide of tin, etc.) Some of the powdered substance is heated upon charcoal in the flame of oxidation, and moistened with a drop of the solution of the nitrate of cobalt, when the oxidation flame is thrown upon it. Alumina gives a pure blue color, the oxide of zinc a bright green, magnesia a light red, and the oxide of tin a bluish-green color ”

“ In the last case it usually is in needle-like crystals growing through calcite crystals, as at St. Louis, Mo., Keokuk, Iowa, and Antwerp, N. Y.
The Cobalt Group
As a metal, cobalt is hard, brittle, and of a grayish color, tinged with red. It was not recognized as a separate element until 1735, and even today is one of the minor metals. Cobalt, chromium and a little tungsten make the alloy stellite, which has come into large use in making high-speed tools. The oxide of cobalt (CoO) is “smalt,” used to give the blue color to porcelain, pottery, glass, tiles, etc. ”

“ Next, the lighter particles are carried off by water, and the cobalt is put into a reverberatory furnace, terminating in a long horizontal gallery; through which the arsenic, usually mixed with the mineral, sublimes: farther, the cobalt is frequently stirred with long iron hooks or rakes, till it ceases to emit any fumes ”

“ The cobalt compounds which are to be used in colour making must be free from iron, nickel and arsenic, which would detract from the cleanness of the colours. If the precipitate produced by soda contains iron it is mixed with excess of solution of oxalic acid, and after a few hours the cobalt oxalate is filtered from the liquid, in which all the iron is dissolved. The cobalt oxalate can then be converted into nitrate or chloride by treatment with nitric or hydrochloric acids. ”

“ Small quanti ties of cobalt, nickel, and copper ores, when associated with lead and silver ores, are in like manner gradually accumulated in a regulus by passing the regulus of the first fusion several times through the smelting furnace, whereby the lead and silver are in great part removed. The treatment of these purified and enriched products is conducted ou the large scale in a somewhat similar manner to a chemical analysis, in order to obtain both cobalt and nickel. The speiss, or regulus, is calcined and treated with strong hydrochloric acid to dissolve the oxides formed. ”

“ Nitrate of Cobalt.— (CoO, NO5) .—This salt can be prepared by dissolving pure oxide of cobalt in diluted nitric acid, and evaporating to dryness with a low heat. The dry residue should be dissolved in ten parts of water, and filtered. The filtrate is now ready for use, and should be kept in a bottle with a glass stopper. If the pure oxide of cobalt cannot be procured, then it may be prepared by mixing two parts of finely powdered glance of cobalt with four parts of saltpetre, and one part of dry carbonate of potassa with one part of water free from carbonate of soda. ”

“ Cobalt green, or Rinman s green, is a mixture of the oxides of zinc and cobalt produced from the solu tions of their sulphates by precipitation with carbonate of sodium and ignition. In analysis cobalt is always determined as protoxide, but the separation from the metals with which it is usually associated, especially nickel, is a difficult and tedious operation. ”

“ A metal found in various combinations, from which various colouring matters are obtained of great use in the arts. Cobalt blue, a beautiful blue pigment, is obtained by mixing a salt of pure cobalt with a solution of pure alum, precipitating the liquid by an alkaline carbonate, washing the precipitate with care, drying and igniting it strongly. A fine green, known as Rinmann’s green, is similarly prepared. The chloride, the nitrate, and the sulphate of cobalt form sympathetic inks, which only become visible when the moisture is absorbed by the application of heat. ”

“ Mix equal parts of oxide of cobalt or roasted Cornish cobalt ore, and soft soap, and expose them to a violent heat in a covered crucible.
3. Pass hydrogen gas over oxide of cobalt strongly heated in a porcelain tube.
Prop., Use, &c. Cobalt is a white, brittle metal; unchanged in the air; feebly acted on by dilute hydrochloric and sulphuric acids; has a high melting-point, and is strongly magnetic; sp. gr. 8·5. It is seldom employed in the metallic state, from the great difficulty of reducing its ores, but its oxide (black oxide) is477 largely employed in the arts. ”

“ They are all red, have a fine fracture, and are much more tenacious than copper—even as high as from fifty to one hundred per cent more so, according to the proportion of cobalt. Five per cent of cobalt is enough to give an alloy of great resistance. ”

“ COBALTITE, a mineral with the composition CoAsS, cobalt sulpharsenide. It is found as granular to compact masses, and frequently as beautifully developed crystals, which have the same symmetry as the isomorphous mineral pyrites, being cubic with parallel hemihedrism. The usual forms are the cube, octahedron and pentagonal dodecahedron {210}. The colour is silver-white with a reddish tinge, and the lustre brilliant and metallic, hence the old name cobalt-glance; the streak is greyish-black. The mineral is brittle, and possesses distinct cleavages parallel to the faces of the cube ”

“ With tin it forms a somewhat ductile alloy of a violet colour. The presence of cobalt in the alloy of copper, zinc, and nickel, known as German silver, is objectionable, as it renders it hard and difficult to roll. The chief use of cobalt in the arts is for the preparation of colours. The protoxide has an intense colouring power when vitrified, and forms the basis of all the blue colours used in glass and porcelain manufacture. The purity of the tint is much affected by traces even of other metallic oxides, especially those of iron, nickel, or copper. ”

“ The best known sympathetic inks consist of solutions of cobalt salts, the writing done with which changes on heating from a nearly invisible pink to blue. This peculiarity of cobalt to form two series of salts containing different amounts of water was discovered in 1715 by Waiz.
Other compounds that may be used as sympathetic writing fluids include tannin, which forms ordinary ink on the addition of iron sulphate; cobalt nitrate which becomes blue on adding oxalic acid, and gold chloride which gives a purple colour with tin chloride. ”

“ Practically the entire Canadian output, most of which is smelted at plants in southern Ontario, is exported to England and the United States.
The cobalt can be plainly seen in the ore when the rock is exposed to the weather. It is of a steel-gray colour tinged with rose-pink, and where it occurs in the form of a powder it looks exactly like rouge. When heated it turns a beautiful blue. Arsenic and other elements are often found mixed with the cobalt-silver ore, and the region has deposits of nickel, copper, and lead. ”

“ It dissolves in acids forming cobaltous salts, and on exposure to air it rapidly absorbs oxygen, turning brown in colour. A. de Schulten (Comptes Rendus, 1889, 109, p. 266) has obtained it in a crystalline form; the crystals have a specific gravity of 3.597, and are easily soluble in warm ammonium chloride solution. Cobalt sesquioxide, Co2O3, remains as a dark-brown powder when cobalt nitrate is gently heated. Heated at 190–300° in a current of hydrogen it gives the oxide Co3O4, while at higher temperatures the monoxide is formed, and ultimately cobalt is obtained. ”

“ They easily oxidise when in the state of powder. When the chlorides of nickel and cobalt are heated in a stream of hydrogen, the metal is deposited in brilliant scales. Nickel is always much more easily and quickly reduced than cobalt. Nickel melts more easily than cobalt, and this even furnishes a means of testing the heating powers of a reverberatory furnace. Cobalt fuses at a temperature only a little lower than that at which iron does. In general, cobalt is nearer to iron than nickel, nickel being nearer to copper. ”

“ As in the series iron, cobalt, nickel, nickel gives NiO and Ni2O3, whilst cobalt and iron give higher and varied forms of oxidation, so also among the platinum metals, platinum and palladium only give the forms RX2 and RX4, whilst rhodium and iridium form another and intermediate type, RX3, also met with in cobalt, corresponding with the oxide, having the composition R2O3, besides which they form an acid oxide, like ferric acid, which is also known in the form of salts, but is in every respect unstable. ”

“ There is even a magnetic oxide among the chromium compounds, such being unknown in the other series. Nickel easily becomes passive in strong nitric acid. It absorbs hydrogen in just the same way as iron. In short, in the series Cr, Mn, Fe, Co, and Ni, there are many points in common although there are many differences, as will be seen still more clearly on becoming acquainted with cobalt and nickel.
In nature cobalt is principally found in combination with arsenic and sulphur. Cobalt arsenide, or cobalt speiss, CoAs2, is found in brilliant crystals of the regular system, principally in Saxony. ”

“ An office, boarding house, stables, corrals, etc., had been built for the accommodation of men and animals. In addition to this I found a complete assay office and chemical laboratory, and here Dr. Endlich was experimenting with the rich cobalt and nickel ores. As a result of his labors in this direction he exhibited several bars of cobalt speiss containing a very high value in silver. The assorted ore contains from 7 to 15 per cent in cobalt, 2 to 3 per cent nickel, and from 1,000 to 1,400 ounces silver per ton. ”

“ The atomic weights of cobalt and nickel, of rhodium, ruthenium, and palladium, and of osmium, iridium, and platinum, are very close to each other, and their properties are also very much alike—the differences are not very perceptible. And if the properties of atoms are a function of their weight, many ideas which have more or less rooted themselves in chemistry must suffer change and be developed and worked out in the sense of this deduction. ”

“ From phosphate of cobalt a beautiful blue pigment is produced, called Thenard’s blue. It is said to have all the characters of ultramarine. Oxide of cobalt has the property of colouring glass blue; hence a glass formed of this oxide under the name of smalt is the blue colouring matter used for ornamenting porcelain and earthenware, for staining glass, for painting on enamel, &c. ”

“ When the powdered alumina compounds are strongly ignited in the oxidizing flame, then moistened with nitrate of cobalt, and re-ignited in the oxidizing flame, an infusible mass is left, which appears, when cooled, of an intense blue color. The presence of colored metallic oxides, in considerable quantity, will alter or suppress this reaction. The silicates of the alkalies produce, in a very strong heat, or continued heat, with nitrate of cobalt, a pale blue color. The blue color produced by alumina is only distinctly visible by daylight ”