DEFINITION
Cobalt- a chemical element located in the fourth period in the VIIIB group of the Periodic Table D.I. Mendeleev.
The serial number is 27. The structure of the atom is shown in fig. 1. Metal of the d-family.
Rice. 1. Scheme of the structure of the cobalt atom.
Under normal conditions, cobalt is a white substance with a yellowish tint, it glistens. Able to exist in the form of several modifications, each of which is stable in a certain temperature range. Up to 430 o C, α-cobalt with a hexagonal close-packed lattice is stable, above 430 o C - β-cobalt with a face-centered cubic lattice.
The molar mass of cobalt is 58.9332 g/mol. This value indicates the ratio of the mass of a substance (m) e number of moles of a given substance (n), denoted by M and can be calculated by the formula:
In other words, the molar mass of a substance is the mass of 1 mol of a given substance, expressed in g/mol or kkmol.
Cobalt cannot exist in the form of a gas, only in the form of a solid, therefore, to find the value of its molar mass, you cannot use the value of the molar volume or make calculations using the Mendeleev-Clapeyron formula.
Examples of problem solving
EXAMPLE 1
| Exercise | Cobalt weighing 2.95 g was dissolved in hydrochloric acid, and a cobalt (II) salt was formed, hydrogen sulfide was passed through the resulting solution. Determine the mass of the precipitate formed. |
| Solution | Let's write the reaction equations, which are mentioned in the condition of the problem: Co + 2HCl dilute = CoCl 2 + H 2 (1); CoCl 2 + H 2 S = CoS↓ + 2HCl (2). Let's find the amount of cobalt substance that reacted (molar mass - 59 g / mol): n(Co) = m(Co) / M(Co); n (Co) = 2.95 / 59 = 0.044 mol. According to equation (1) n (Co): n (CoCl 2) \u003d 1: 1, therefore, n (Co) \u003d n (CoCl 2) \u003d 0.044 mol. Then, the number of moles of cobalt (II) sulfide (precipitate) will also be equal to 0.044 moles, since n (CoCl 2) : n (CoS) = 1:1. The mass of cobalt (II) sulfide is (molar mass - 91 g / mol): m(CoS)=n(CoS)×M(CoS); m (CoS) = 0.044 × 91 = 4.004 g. |
| Answer | The mass of cobalt (II) sulfide is 4.004 g |
EXAMPLE 2
| Exercise | The standard electrode potential of nickel is greater than that of cobalt (E 0 Co 2+ / Co 0 \u003d -0.27 V, E 0 Ni 2+ / Ni 0 \u003d -0.25 V). Will this ratio change if we measure the potential of nickel in a solution of its ions with a concentration of 0.001 mol / dm 3, and the potential of cobalt - in a solution with a concentration of 0.1 mol / dm 3? |
| Solution | Let us determine the electrode potentials of cobalt and nickel under given conditions using the Nernst equation: E ’ Ni 2+ / Ni 0 \u003d E 0 Ni 2+ / Ni 0 - 0.059 / n ×lg (a Ni 2+ / a Ni 0); E ’ Ni 2+ / Ni 0 \u003d -0.25 + (0.059 / 2) × lg10 -3; E ’ Ni 2+ / Ni 0 \u003d -0.339 V. E ’ Co 2+ / Co 0 \u003d E 0 Co 2+ / Co 0 - 0.059 / n × lg (a Co 2+ / a Co 0); E ’Co 2+ /Co 0 \u003d -0.27 + (0.059 / 2) × lg10 -1; E ’Co 2+ / Co 0 \u003d -0.307 V. |
| Answer | Under given conditions, the potential of cobalt is greater than the potential of nickel |
Several hundred years ago, the German province of Saxony was at that time a major center for the extraction of silver, copper and other non-ferrous metals. In the mines there, it happened to find ore that, by all external signs, seemed to be silver, but when smelted, it was not possible to obtain precious metal from it. Worse, when such ore was roasted, a poisonous gas was released that poisoned the workers. The Saxons explained these troubles by the intervention of evil spirits, the insidious underground dwarf kobold. From him also came other dangers, lying in wait for the miners in the dungeons. In those days in Germany, even prayers were read in churches for the salvation of miners from the evil spirit of kobold ... And over time, when the Saxons learned to distinguish "impure" ore from silver, they called it "kobold".
In 1735, the Swedish chemist Georg Brandt isolated an unknown metal from this "impure" ore, gray with a faint pinkish tint. The name "kobold", or "cobalt", was preserved for him.
From Venetian glass to traffic lights
In Brandt's dissertation on the new metal, it was said, in particular, that metal can be used to make safra, a paint that gives glass a deep and very beautiful blue color. But even in ancient Egypt, blue glass was known, made according to carefully concealed recipes.
In the Middle Ages, none of the states of Europe could compete in the production of glass with the Venetian Republic. In order to protect the secrets of cooking colored glass from other people's curiosity, the government of Venice in the XII century. by special decree transferred all glass factories to the secluded island of Murano. About how the secrets of production were protected there, you can get some idea from such a story. One day, an apprentice named Giorgio Belerino fled from the island, and soon a glass workshop burned down in one of the German towns. Its owner - his name was Belerino - was stabbed to death with a dagger...
And yet, despite such cruel measures, the secrets of colored glass melting became known in other states. In 1520, Weidenhammer in Germany found a way to prepare paint for blue glass and began to sell it at a high price ... to the Venetian government! After another 20 years, the Bohemian glassmaker Schurer also began to make blue paint from some kind of ore known to him alone. With his help, such paint began to be produced in Holland. Contemporaries wrote that the glass was painted with "zaffer", but no one knew what this product was. Only a century later (in 1679), the famous chemist Johann Kunkel described in detail the process of obtaining paint, but it remained unknown what kind of ore it was made from, where to look for this ore, and what constituent of it had a coloring property.
It was only after Brandt's research that it was found out that safr, or zaffer, a product of calcining cobalt-rich ore, contains cobalt oxides and many oxides of other metals. Fused then with sand and potash, zaffer formed smalt, which was the paint for glass. There was little cobalt in smalt - only 2...7%. But the coloring power of cobalt oxide turned out to be great: already 0.0001% of it in the charge gives the glass a bluish tint.
Glass makers of the Middle Ages used the properties of cobalt unconsciously, having found them purely by experience. Of course, this cannot even in the smallest degree belittle in our eyes the remarkable art of these workers.
In addition to smalt, there are other cobalt dyes: blue aluminum-cobalt paint - tenar blue; green - a combination of oxides of cobalt, chromium, aluminum, magnesium and other elements. These paints are beautiful and sufficiently resistant at high temperatures, but do not always have good hiding power. Their value is much less than smalts. Something else deserves attention: the variability of the color of cobalt compounds.
The miracles of the transformation of colors have been known since the 16th century. A professor at the University of Basel, a chemist and physician, Paracelsus showed a picture he had painted. She depicted a winter landscape - trees and hillocks covered with snow. Having let the audience see enough, the professor slightly warmed up the picture, and right before everyone's eyes, the winter landscape was replaced by summer: the trees were dressed in foliage, grass was green on the hillocks. It gave the impression of a miracle.
For a modern chemist, the story of Paracelsus's painting looks pretty simple. Such an effect could be given, in particular, by cobalt paints. Cobalt chloride, to which an appropriate amount of nickel chloride is added, is almost colorless. But when heated, these salts lose their water of crystallization, and their color changes.
In 1737, a French chemist discovered the property of cobalt salts to be colored by heat and used them as sympathetic inks. What they write on paper becomes visible only after the paper is heated. Now this feature of cobalt salts is of practical importance in laboratory technology: porcelain crucibles are labeled with a solution of cobalt salts. After heating, such a mark clearly appears on the white surface of the porcelain.
The coloring of glasses with cobalt compounds is of no small importance in our time, although there are cheaper dyes.
For technical purposes, glasses are often needed that absorb and transmit rays of a certain color. Such glasses are needed in photography, signaling, colorimetric analysis and other applications. Nowadays, smalt is not used, but cobalt oxide is used directly, which is introduced into the composition of the charge loaded into the glass melting furnace.
Glasses used for signal lights should give a sharp, distinct light. It is necessary to exclude the possibility of erroneous perception of the signal even in conditions of poor visibility, even at high transport speeds and the imperfection of human vision. And for this it is necessary that the glasses of light signaling devices transmit only light of a precisely defined wavelength.
Glasses colored with cobalt oxide have no rivals in transparency, and the addition of negligible amounts of copper oxide to such glass gives it the ability to block some rays of the red and violet parts of the spectrum. For photochemical studies, glasses are sometimes needed that do not transmit yellow and orange rays at all. This condition is met by cobalt-ruby glasses: a heated glass colored red by copper compounds, the so-called copper ruby, is superimposed on the blue glass tinted with cobalt. It is well known to use cobalt oxide to impart a beautiful, very stable dark blue color to porcelain and enamelware.
Cobalt is an alloying metal
In 1912, they wrote about cobalt: “Until now, metallic cobalt is of no interest from the point of view of consumption. There have been attempts to introduce cobalt into iron and prepare special steels, but the latter have not yet found any application. Indeed, at the beginning of our century, the first attempts to use cobalt in metallurgy were unsuccessful. It was known that chromium, tungsten, vanadium give steel high hardness and wear resistance at elevated temperatures. At first, the impression was that cobalt was not suitable for this purpose - the steel was poorly hardened, more precisely, the hardening penetrated into the product to a very shallow depth. Tungsten, chromium and vanadium, combining with carbon dissolved in steel, form solid carbides, while cobalt, as it turned out, contributes to the release of carbon in the form of graphite. In this case, the steel is enriched with unbound carbon and becomes brittle. In the future, this complication was eliminated: the addition of a small amount of chromium to cobalt steel prevents graphitization; such steel is well hardened.
Now cobalt, like tungsten, is indispensable in metalworking - it serves as the most important component of high-speed tool steels. Here, for example, is the result of comparative tests of three incisors. In the steel from which they were made, carbon, chromium, vanadium, tungsten and molybdenum were contained in the same quantities, the difference was only in the content of cobalt. In the first, vanadium steel, there was no cobalt at all, in the second, cobalt, it was 6%, and in the third, supercobalt, 18%. In all three experiments, a steel cylinder was sharpened with a cutter. The thickness of the chips removed was the same - 20 mm, the cutting speed was the same - 14 m/min.
What did the experiment show? The vanadium cutter blunted after 7m, the cobalt 10m, and the supercobalt cutter went 1000m and was in good condition! Thus, for a sharp increase in wear resistance and cutting properties of steel, cobalt must be included in its composition in significant quantities.
In 1907, iron-free hard alloys appeared in industry - stellites (from the Latin word stella - star). One of the best stellites contained more than 50% cobalt. And in hard alloys, which in our time have become the most important material for metal-cutting tools, cobalt plays an important role. Tungsten or titanium carbide, the main component of the hard alloy, is sintered in a mixture with cobalt metal powder. Cobalt connects grains of carbides and gives the whole alloy a high viscosity, reduces its sensitivity to shocks and impacts.
Hard alloys can serve not only for the manufacture of cutting tools. Sometimes it is necessary to weld a hard alloy onto the surface of parts that are subject to heavy wear during machine operation. Such a cobalt-based alloy can increase the service life of a steel part by 4 to 8 times.
Magnetic properties
The ability to retain magnetic properties after a single magnetization is characteristic of only a few metals, including cobalt. A very important technical requirement is imposed on steels and alloys from which magnets are made: they must have a large coercive force, otherwise, resistance to demagnetization. Magnets must also be resistant to temperature effects, vibration (which is especially important in motors), and easy to machine.
Under the action of heat, the magnetized metal loses its ferromagnetic properties. The temperature at which this happens (Curie point) is different: for iron it is 769°C, for nickel it is only 358°C, and for cobalt it reaches 1121°C. Back in 1917, a steel composition with improved magnetic properties was patented in Japan. The main component of the new steel, called Japanese steel, was cobalt in a very large amount - up to 60%. Tungsten, molybdenum or chromium give magnetic steel high hardness, and cobalt increases its coercive force by 3.5 times. Magnets made of such steel are 3-4 times shorter and more compact. And one more important property: if tungsten steel loses its magnetic properties under the action of vibrations by almost a third, then cobalt - by only 2 ... 3.5%.
In modern technology, especially in automation, magnetic devices are used literally at every step. The best magnetic materials are cobalt steels and alloys. By the way, the property of cobalt not to demagnetize under the action of vibrations and high temperatures is of no small importance for rocket and space technology.
Modern requirements for permanent magnets are extremely diverse. And one of the main ones is the minimum weight with maximum “strength”. In recent decades such magnets have been invented. These are alloys called "magnico" and "alnico" - by the initial letters of the names of the metals of which they are composed: the first of magnesium, nickel and cobalt, the second of aluminum, nickel and cobalt. In such magnets there is no iron at all - a metal, the very name of which we are accustomed to consider from the school bench as inseparable from ferromagnetism. The properties of these alloys seem extraordinary: a magnet weighing 100...200 g holds a load of 20...30 kg! Very strong permanent magnets are also obtained from intermetallic compounds of cobalt with some rare earth elements (for example, SmCo 5, etc.).
Cobalt and wildlife
Before talking about why not only engineers, but also agronomists and doctors are interested in cobalt, a few words about one not quite ordinary service of element No. 27. Even during the First World War, when the militarists made the first attempts to use poisonous substances, it became necessary to find substances that absorb carbon monoxide. This was also necessary because very often there were cases of poisoning of gun servants with carbon monoxide released during firing.
In the end, a mass was composed of oxides of manganese, copper, silver, cobalt, called hopcalite, which protects against carbon monoxide, which in its presence oxidizes already at room temperature and turns into non-toxic carbon dioxide. Hopkalite is a catalyst; it only contributes to the oxidation reaction 2CO + O 2 → 2CO 2 without being part of the final products.
And now - about cobalt in wildlife.
In some regions of different countries, including ours, the disease of livestock, sometimes called dryness, was notorious. Animals lost their appetite and lost weight, their hair stopped shining, their mucous membranes became pale. The number of red blood cells (erythrocytes) in the blood dropped sharply, and the hemoglobin content sharply decreased. The causative agent of the disease could not be found, but its prevalence created the complete impression of an epizootic. In Austria and Sweden, an unknown disease was called swamp, shrub, coastal. If healthy animals were brought to the area affected by the disease, then in a year or two they also fell ill. But at the same time, cattle taken out of the region of "epidemics" did not infect the animals that communicated with them and soon recovered themselves. So it was in New Zealand, and in Australia, and in England, and in other countries. This circumstance forced to look for the cause of the disease in the feed. And when, after painstaking research, it was finally established, the disease received a name that accurately defines this cause - acobaltosis ...
Faced with acobaltosis, with the absence (or lack) of cobalt in the body, and our scientists.
One day, a letter arrived at the Academy of Sciences of the Latvian SSR, informing that in the area of one of the swamps not far from Riga, cattle were affected by dryness, but the forester living there had all the cows well-fed and gave a lot of milk. Professor Ya.M. went to the forester. Berzin. It turned out that earlier the forester's cows were also sick, but then he began to add molasses (feed molasses - a waste of a sugar factory) to their feed, and the animals recovered. The study showed that a kilogram of molasses contains 1.5 mg of cobalt. This is much more than in plants growing on swampy soils. A series of experiments on rams suffering from dryness dispelled all doubts - the absence of trace amounts of cobalt in food - this is the cause of a terrible disease. At present, factories in Leningrad and Riga produce special tablets for additions to livestock feed, which protect against dryness in those areas where the amount of the trace element cobalt in the soil is insufficient for adequate nutrition of animals.
It is known that the human body needs iron: it is part of the hemoglobin in the blood, with the help of which the body absorbs oxygen during breathing. It is also known that green plants need magnesium, as it is part of chlorophyll. And cobalt - what role does it play in the body?
There is also such a disease - malignant anemia. The number of red blood cells decreases sharply, hemoglobin decreases ... The development of the disease leads to death. In search of a remedy for this ailment, doctors discovered that raw liver, eaten, delays the development of anemia. After many years of research, it was possible to isolate a substance from the liver that contributes to the appearance of red blood cells. It took another eight years to find out its chemical structure. For this work, the English researcher Dorothy Crowfoot-Hodgkin was awarded the Nobel Prize in Chemistry in 1964. This substance is called vitamin B 12. It contains 4% cobalt.
Thus, the main role of cobalt salts for a living organism has been clarified - they are involved in the synthesis of vitamin B 12. In recent years, this vitamin has become a common remedy in medical practice, which is injected into the muscles of a patient whose body lacks cobalt for one reason or another.
And one more service of cobalt in medicine is the treatment of malignant tumors with radioactive radiation. Now all over the world for irradiation of tissues affected by cancer (in cases where such treatment is generally possible) a radioactive isotope of cobalt - 60 Co, which gives the most homogeneous radiation, is used.
In the apparatus for irradiating deep-seated malignant tumors, the "cobalt gun" GUT-400 (gamma therapeutic unit), the amount of cobalt-60 corresponds in its activity to 400 g of radium. This is a very large value, there is no such amount of radium in any laboratory. But it is high activity that allows attempts to treat tumors located deep in the patient's body.
Radioactive cobalt is used not only for medicinal purposes. Installations similar to the medical "gun" are used in industry to control the level of solutions in devices operating at high temperatures and pressures, and in many other cases.
Cobalt in space
Talking about this or that metal, it is impossible not to mention what it has to do with ultra-high-speed, high-altitude and space flights. In these branches of technology, the highest demands are placed on the materials used. We have to take into account not only the strength, weight and other "ordinary" values. It is necessary to take into account the conditions: rarefaction of the atmosphere and space vacuum, and on the other hand, strong aerodynamic heating, the possibility of sudden temperature changes, thermal shocks.
It would seem that "superfast" structures should be made from the most refractory materials, such as tungsten, molybdenum, tantalum. These metals, of course, play a prominent role, but it should not be forgotten that they also have disadvantages that limit the possibilities of application. At high temperatures, they oxidize relatively easily. Their processing is difficult. Finally, they are expensive. Therefore, they are used when other materials cannot be dispensed with, and alloys based on nickel or cobalt work instead of them in many nodes.
Nickel-based alloys have received the widest application in aviation and space technology. When a well-known metallurgist was asked how he creates high-temperature alloys, he replied: "I simply replace iron in steels with nickel."
For the same purpose, cobalt-based alloys are used. The high prevalence of nickel alloys is mainly due to their greater knowledge and lower cost. The operational properties of alloys based on nickel and cobalt are almost identical. But the “strength mechanisms” are different. The high strength of nickel alloys with titanium and aluminum is explained by the formation of a hardening phase with the composition Ni 3 Al(Ti); the more titanium and aluminum in the alloy, the higher its mechanical properties. But at high operating temperatures, the particles of the hardening phase go into solution, and then the alloy rather quickly weakens.
Cobalt alloys, on the other hand, owe their heat resistance to the formation of refractory carbides. These carbides do not dissolve in solid solution. They also have low diffusion mobility. True, the advantages of such alloys over nickel ones appear only at temperatures from 1038°C and above. The latter should not be embarrassing: it is known that the higher the temperature that develops in the engine, the greater its efficiency. Cobalt alloys are good for the most efficient high temperature engines.
In the construction of aircraft turbines, cobalt alloys are used, which contain from 20 to 27% chromium. This achieves a high "scaling resistance" of the material, which makes it possible to dispense with protective coatings. Chromium, by the way, is the only element that increases the resistance of cobalt against oxidation and at the same time its strength at high temperatures.
Under laboratory conditions, the properties of nickel and cobalt alloys were compared under the action of variable temperature loads (thermal shock). Tests have shown that cobalt alloys are more "shock resistant". It is not surprising, therefore, that specialists in space technology are paying more and more attention to the alloys of element No. 27. This, so to speak, is an interest with a perspective. Let's try to explain what this means, at least with one example.
Manned space flights are becoming more and more familiar. But so far, on our TV screens, we see only rockets that receive energy as a result of the oxidation reaction of certain fuels. It is unlikely that this type of "energy supply" can be considered the only one for the future. Rockets will rise, the thrust of which will be created by other forces. Electrothermal, plasma, ion rockets are under development...
An important component of the propulsion system of any of these systems will, apparently, be an electric generator. High power generator. But, as we know, powerful generators both weigh a lot and have solid dimensions. How to place such a colossus on a "transportable installation"? Or - which is practically more acceptable - how to make a sufficiently powerful and at the same time sufficiently light generator? We need optimal designs and optimal materials for them.
The projects under development include, in particular, a nuclear reactor with heat recovery in a steam turbine. This turbine will be turned not by water vapor, but by mercury vapor (or alkali metal vapor). In a tubular boiler, the heat of the nuclear reaction will vaporize the mercury; mercury vapor, having passed the turbine and having done its job, will go to the condenser, where it will again become a liquid, and then again, making a cycle, will go to the boiler.
Such devices must operate non-stop, without inspection and any repairs for at least 10 thousand hours, i.e. more than a year. Judging by the publications, the boilers of the experimental American generators SNAP-2 and SNAP-8 are made of cobalt alloys. These alloys were used because they are heat-resistant, not subject to amalgamation (do not react with mercury), and corrosion-resistant.
It's on Earth too...
We have not told in all areas of application of cobalt. They did not mention at all, for example, that electrolytic cobalt coatings are in many respects superior to nickel coatings. You can get a cobalt coating of the desired thickness (and even thickness!) Not in an hour, like nickel, but in just 4 minutes. Cobalt coatings are harder, so the cobalt protective layer can be made thinner than the corresponding nickel layer.
The Russian scientist Fedotiev once studied a cobalt alloy (up to 75% cobalt), intended to replace the platinum electrodes of galvanic baths. It turned out that this alloy is not only not inferior to the precious metal, but also surpasses it in terms of insolubility in strong acids, and is incomparably cheaper.
We do not notice that cobalt surrounds us in our everyday life, in everyday life, more specifically - in enamel pots, and not only blue. The now widely known process of enameling tinplate was born in pain. The enamel was applied, but it did not hold well and bounced off the base metal when heated, pushed, or even for no apparent reason. Only when enamel was applied in two layers (primer and enamel), with only 0.6% cobalt in the first layer, did the coating hold firmly. This is explained by the fact that in the process of heating cobalt oxides are reduced by iron to metal; this cobalt, upon further heating, diffuses into iron, forming a hard alloy with it. We only talked about the saucepan, but how many enamelware are used in medicine, pharmaceutical, and chemical industries. And everywhere cobalt, only 0.6%.
The use of cobalt, its alloys and compounds is expanding every day. Recently, for example, they have become needed for the manufacture of ferrites, in the production of "printed circuits" in the radio engineering industry, in the manufacture of quantum generators and amplifiers. This is a metal with a great present and a great future.
Some statistics
Interesting figures that give some idea of what cobalt is spent on in the industrialized countries of the West. Here are the statistics for recent years (in%):
| Magnetic alloys | 27 |
| Heat resistant materials | 21,5 |
| Paints and varnishes | 13 |
| Wear-resistant and corrosion-resistant alloys for the chemical and metallurgical industries | 8,5 |
| Ceramics and enamels | 7 |
| Low expansion alloys for instrumentation, low modulus alloys for springs, etc. | 7 |
| High yield strength steels (in aircraft and rocket manufacturing) | 6,5 |
| Powder of metallic cobalt for the manufacture of hard alloys | 4 |
| Catalysts in chemical production and trace elements in agriculture (livestock) | 3 |
| High speed steels | 2,5 |
These figures refer to the early 70s, but it is unlikely that anything has changed significantly in recent years. Element No. 27 did not find ultra-new areas of application in these years. It is known that in 1975 in the United States the demand for cobalt fell by almost a quarter compared to 1974. However, the economic crisis has had a similar impact on the production and consumption of many metals.
In the world, according to American data, in 1975 more than 20 thousand tons of cobalt were obtained. Before the start of World War II, cobalt production barely exceeded 3 thousand tons. The largest supplier of cobalt to the world market is the Republic of Zaire. The subsoil of Canada, the USA, France, and Zambia are quite rich in cobalt. In the Soviet Union, there are cobalt ores in the Urals, in Kazakhstan, in Eastern Siberia. Cobalt-containing copper-nickel ores are found on the Kola Peninsula and in the Norilsk region.
The future, one must think, will reveal to us more than one valuable property of element No. 27.
To the question of the name
Regarding the harmfulness of the creatures by whose name cobalt got its name, there is an opinion that is diametrically opposed to that given in the article about element No. 27. Check out the following document:
We are kindred to good kobolds;
Mountain surgeons, appreciating their work.
We drill them to the best of our ability, -
We bleed from the ore veins;
We are hoarding metals.
And we call affectionately from the darkness.
To inspire the traveler:
"Happy journey! Happy way!”
This quite positive official characteristic was given to the underground gnomes by a fairly authoritative expert on the German Middle Ages - Johann Wolfgang Goethe. You can find it in the second part of Faust.
In the tomb of Tutankhamun
Already in ancient times, people knew how to make colored glass and smalts, including blue ones. The remains of dishes, mosaics, blue glass decorations, archaeologists find in many centers of ancient civilizations.
However, in most cases - this is indisputably evidenced by the results of chemical analysis - these glasses are colored with copper compounds, not cobalt. For example, in the tomb of the Egyptian pharaoh Tutankhamun, many objects made of blue glass were found. But only one of them turned out to be colored with cobalt, all the rest - with copper.
Of course, there is nothing to be surprised here - copper minerals are found on our planet much more often than cobalt ones.
Teacher and pupil
Georg Brandt, who discovered cobalt, began to study chemistry almost from childhood, helping his father, first a pharmacist and then a manager of metallurgical enterprises, to set up experiments.
Brandt spent his student years in the Dutch city of Leiden. Here he studied medicine and chemistry under the famous chemist, botanist and physician Hermann Boerhaave.
Boerhaave was the first among scientists to use a magnifying glass and a thermometer in his research. His lectures enjoyed the widest popularity - even the Russian Tsar Peter I visited them. Boerhaave did a lot to refute the various conjectures of the alchemists, in this he showed rare persistence. For example, wanting to prove that, contrary to the assertions of alchemists, mercury does not turn into a solid body when heated for a long time, Boerhaave heated mercury in a closed vessel for ... 15 years.
After studying in Leiden for 3 years, Brandt went to Reims, where he received a doctorate in medicine, then to the Harz to study mining and metallurgy. Only then did he return to Sweden.
Brandt also carried out his most important research in the laboratories of the Mint. (By the way, in Russia one of the first chemical laboratories was located at the Mint.) Brandt studied arsenic and its compounds, soda and common salt; organized the production of Swedish brass based on local zinc. But the discovery of cobalt brought the greatest fame to Brandt, of course.
From the diary of a discoverer
"Just as there are six types of metals, there are - I have proven this with reliable experiments ... - six types of semi-metals ... I had the good fortune to be the discoverer of a new semi-metal called cobalt regulus, which was previously confused with bismuth ... "
The heavy metal, which is cobalt, was discovered by the Swedish chemist G. Brandt in 1735. At that time, metallurgists were faced with the task of deeper purification of mined ores in order to improve the quality of steel being smelted. The silvery substance with a pink tinge was originally called kobold. Decades later, the name cobalt was assigned to this metal.
Cobalt: physical and chemical properties
The chemical composition of metallic cobalt produced in ingots is standardized by GOST 123-78:
This element is stable in simple connections, relatively resistant to air and water (under normal conditions). At the same time, it begins to oxidize in air at t = 300 ° C. After heating, cobalt is combined with halogens to obtain halides. As for the interaction of the metal with hydrochloric and sulfuric acids, under such exposure, cobalt slowly dissolves, releasing hydrogen and transforming into cobalt chloride (CoCl 2) and cobalt sulfate (CoSO 4). If this substance is immersed in nitric acid, it will be possible to obtain nitrate - Co (NO 3) 2.
The following table will help compare the physical properties of Co with metals such as iron (Fe) and nickel (Ni):
Magnetic properties of cobalt
This metal is characterized by the ability to retain magnetization. As a result, cobalt becomes an indispensable "participant" in magnetic alloys that have a relatively high resistance to demagnetization. Moreover, it is Co that makes the magnets resistant to temperature changes and vibrations, while making the product available for machining.
The main application of cobalt-based magnetic alloys is noted in the manufacture of a variety of electrical products: transformers, electric motor cores, etc. An excellent example of the excellent magnetic properties of Co can be considered Japanese steel: 60% cobalt content gives a resistance to demagnetization equal to only 2-3% at the strongest vibrations.
Cobalt: application
Cobalt is an alloying metal, so it finds its main application in the creation of various alloys. In particular, it significantly improves the heat-resistant properties of steels, their wear resistance and hardness, increases the toughness of the metal and reduces the sensitivity of the alloy to vibrations, shocks and shocks. At the same time, cobalt 2 oxide is an excellent catalyst for chemical reactions. 
Due to its unique chemical and physical characteristics, cobalt is in demand both in the aviation and space industries, where it gradually replaces nickel (at t> 1038 ° C, the nickel alloy loses its strength, which cannot be said about metals with cobalt impurities).
A separate area where cobalt appears is the use in medicine. This element is trusted to work on the synthesis of muscle proteins, the activation of enzymes, the increase in the glycolytic activity of the blood, and the stimulation of hematopoiesis. Drugs such as coamide, cobaltamine, cobaltin or ferkoven contain cobalt in their basis and help stimulate erythropoiesis in anemia.
Cobalt finds wide and varied applications in various industries, agriculture and medicine, which is associated with the remarkable properties of this metal and its alloys.
In its pure form, cobalt is used relatively little: only in the form of radioactive 60 Co in industrial γ -defectoscopy and γ -therapy and for the manufacture of measuring instruments.
About 80% of cobalt is spent on obtaining superhard, heat-resistant, tool and wear-resistant alloys, as well as permanent magnets. These alloys are used in mechanical engineering, aviation technology, rocket science, electrical and nuclear industries.
As an alloying element, cobalt is used in the production of tungsten high-speed tool steels, which have high strength and provide high machining speeds. As a rule, these steels contain, %: 15-19 W,4Cr , 1 V, 5-13 Co and 0.5-0.8 C. The cutting ability of tool steels is proportional to their cobalt content up to 13%. Cobalt additions to molybdenum steels also improve their cutting properties. The presence of cobalt in high-speed steels does not increase their hardness, but shifts the temperature of the onset of hardness loss to 600°C, while in ordinary steel it decreases from 200°C.
Superhard alloys based on cobalt and chromium - stellites - are widely used.
The chemical composition and hardness of typical stellites are given below:
Cobalt alloys - stellites containing up to 30% Cr, as well as tungsten, silicon and carbon, are used for surfacing on tools and machine parts (without subsequent heat treatment) in order to increase their wear resistance.
Cobalt is widely used as an alloying element in the production of carob-strength steels, as well as heat-resistant cobalt alloys. Wrought Hobalt Alloys System Co-Cr-Ni-Mn , containing up to 50% Co, have high resistance to thermal fatigue and are satisfactorily processed by pressure. The total amount of alloying elements in them reaches 8-9, and their content is 10-25%. The temperature limit for the use of heat-resistant steels is 800-850°C, and for cobalt-based alloys - 1000°C and higher. An example of a cobalt-based heat-resistant alloy is an alloy with a content, %: 12-15 Ni, 18-24 Cr, 8-12 W, 1.25 Mn, 1.1 Si, 0.5 C.
The next group of alloys, in the production of which cobalt is widely used, is refractory heat-resistant alloys obtained by the cermet method based on carbides, silicides, borides of titanium, tungsten, zirconium, niobium, tantalum and vanadium. A feature of these alloys is the high content of cobalt and nickel in them, used for bonding. These alloys are used up to a temperature of 1050-1100°C.
Of considerable interest to the nuclear industry as a structural material for nuclear reactors are stainless steels with low cobalt content (<0,05%).
Cobalt is also widely used to obtain magnetic materials with high magnetic permeability and alloys for permanent magnets (alloys of cobalt with iron, platinum; alloys based on cobalt alloyed with aluminum, nickel, copper, titanium, samarium, lanthanum, cerium). The introduction of cobalt additives in the amount of 0.5-4.0% into alloys helps to reduce the grain size, due to which the coercive force (resistance to demagnetization) and residual magnetization increase. Industrial alloys for Alnico type magnets contain aluminum, nickel, cobalt, and the rest is iron. Individual alloys also include copper and titanium:
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Alnico alloys have high coercive force and magnetic energy. These alloys are used in the manufacture of magnetic bearings, generators and permanent magnet motors.
Cobalt-platinum magnetic alloys containing 50% Co. have the best magnetic properties.
Magnetic alloy containing 49% Co, 49% Fe and 2% V, has a high residual magnetic induction, and in addition, it can be rolled from a thickness of 2.31 to 0.0075 mm withoutintermediate annealing and loss of plasticity. Its use provides an increase in the efficiency of spacecraft engines.
Cobalt is also one of the elements of a large number of acid-resistant alloys. So, the best for the manufacture of insoluble anodes is an alloy composition. %: 75 Co, 13 Si , 7 Cr and 5 MP. This alloy is more resistant to nitric and hydrochloric acids than platinum. Good resistance in concentrated hydrochloric acid at a temperature of 80 ° C has an alloy of composition,%: 56 Ni, 19.5 Co, 22 Fe, and 2.5 Mn.
Cobalt is used in conjunction with nickel for electrolytic coating of various products to give them corrosion-resistant properties. The anode during electrolysis is a nickel alloy with 1-18% Co, depending on the chromium content in the bath, the electrolyte is sulfate o-chloride solutions. During the electrodeposition of cobalt or nickel doped with phosphorus in an amount of up to 15%, hard, corrosion-resistant and shiny coatings with good ductility are formed, reliably adhering to the base metal. Such coatings are applied to gauges, cylinder walls, piston rings and valve stems.
In the chemical and petrochemical industries, powdered cobalt and its oxide are used as a catalyst in the hydrogenation of fats, in the synthesis of gasoline, in the production of nitric acid, soda and ammonium sulfate.
The use of cobalt in the paint and varnish, glass and ceramic industries is widely known. This area of application of the metal is based on the ability of cobalt oxide, when fused with glass or enamel, to give blue-colored silicates and aluminosilicates, for example, smalt (double silicate of cobalt and potassium). Smalt, due to its high resistance to high temperatures and fusibility, is an indispensable material for painting glass, enamels and other ceramic products.
Other cobalt compounds are also used as dyes. Of the cobalt paints, the following are of interest: blue - cobalt aluminate; violet - anhydrous phosphate salt Co 3 (Р0 4 )2; yellow - Fisher's salt K 3 [Co( NO 2) 6] H 2 0, green - CoOxZnO ; pink, obtained by calcining magnesium carbonate with cobalt nitrate. All these cobalt compounds are used for the production of oil art paints and in ceramic production. Cobalt paints are distinguished by great durability and color stability. Turkish green, or blue-green paint, obtained by calcining cobalt carbonate, chromium oxide and aluminum hydroxide in a ratio of 1:1:2, is used to color porcelain.
Cobalt salts and some cobalt-containing alloys are also used in the glass industry.
Cobalt oxides are used in the enameling of tin. To obtain durable enamel, up to 0.2% cobalt oxides, as well as nickel and manganese, are introduced into the soil composition.
Cobalt combined with silver is used in the manufacture of batteries.
The radioactive isotope 60 Co (with a half-life of T 1/2 = 5.27 years) is widely used as a long-acting source of y-radiation ("cobalt gun"). In technology, it is used for y-defectoscopy, and in medicine - for radiation therapy of tumors. and sterilization of medicines. In addition, 60 Co is used to kill insects in grains and vegetables.
Cobalt salts are used in agriculture as microfertilizers, and also as animal feed.
Cobalt
COBALT-A; m.[German] Kobalt]
1. Chemical element (Co), a silvery-white metal with a reddish tint, harder than iron.
2. The paint is dark blue, which includes this metal.
◁ Cobalt, th, th. K-th ores. K-th steel. K paint.
cobalt(lat. Cobaltum), a chemical element of group VIII of the periodic system. The name is from the German Kobold - brownie, gnome. Silvery white metal with a reddish tint; density 8.9 g / cm 3, t pl 1494ºC; ferromagnetic (Curie point 1121ºC). At normal temperatures in air, it is chemically stable. Minerals are rare, mined from nickel ores. Basically, cobalt is used to obtain cobalt alloys (magnetic, heat-resistant, superhard, corrosion-resistant, etc.). The radioactive isotope 60Co is used as a source of γ-radiation in medicine and technology. Cobalt is important for the life of plants and animals, it is part of vitamin B 12.
COBALTCOBALT (lat. Cobaltum), Co, chemical element with atomic number 27, atomic mass 58.9332. The chemical symbol for the element Co is pronounced the same as the name of the element itself. Natural cobalt is composed of two stable nuclides (cm. NUCLIDE): 59Co (99.83% by weight) and 57Co (0.17%). In the periodic system of elements of D. I. Mendeleev, cobalt is included in group VIIIB and, together with iron (cm. IRON) and nickel (cm. NICKEL) forms in the 4th period in this group a triad of transition metals with similar properties. The configuration of the two outer electron layers of the cobalt atom 3 s 2
p 6
d 7
4s 2
. Forms compounds most often in the oxidation state +2 (valency II), less often in the oxidation state +3 (valence III) and very rarely in the oxidation states +1, +4 and +5 (valencies, respectively, I, IV and V) .
The radius of the neutral cobalt atom is 0.125 nm, the radius of the ions (coordination number 6) Co 2+ - 0.082 nm, Co 3+ - 0.069 nm and Co 4+ - 0.064 nm. The successive ionization energies of the cobalt atom are 7.865, 17.06, 33.50, 53.2, and 82.2 eV. On the Pauling scale, the electronegativity of cobalt is 1.88. Cobalt is a lustrous, silvery-white, heavy metal with a pinkish tint.
Discovery history
Since antiquity, cobalt oxides have been used to color glass and enamels deep blue. Until the 17th century, the secret of obtaining paint from ores was kept secret. These ores in Saxony were called "kobold" (German: Kobold - brownie, an evil dwarf who prevented miners from extracting ore and smelting metal from it). The honor of discovering cobalt belongs to the Swedish chemist G. Brandt (cm. BRANDT Georg). In 1735, he isolated a new silvery-white metal with a faint pinkish tint from the insidious "impure" ores, which he proposed to call "kobold". Later this name was transformed into "cobalt".
Being in nature
In the earth's crust, the content of cobalt is 410 -3% by weight. Cobalt is part of more than 30 minerals. These include carolite CuCo 2 S 4 , linneite Co 3 S 4 , cobalt (cm. COBALTIN) CoAsS, spherocobaltite CoCO 3 , smaltite CoAs 2 and others. As a rule, cobalt in nature is accompanied by its neighbors in the 4th period - nickel, iron, copper. (cm. COPPER) and manganese (cm. MANGANESE (chemical element)). In sea water, approximately (1-7) 10 -10% cobalt.
Receipt
Cobalt is a relatively rare metal, and the deposits rich in it are now practically exhausted. Therefore, cobalt-containing raw materials (often these are nickel ores containing cobalt as an impurity) are first enriched, and a concentrate is obtained from it. Further, to extract cobalt, the concentrate is either treated with solutions of sulfuric acid or ammonia, or processed by pyrometallurgy methods into a sulfide or metal alloy. This alloy is then leached with sulfuric acid. Sometimes, to extract cobalt, sulfuric acid "heap" leaching of the original ore is carried out (crushed ore is placed in high heaps on special concrete platforms and these heaps are poured with a leaching solution from above).
Extraction is increasingly being used to purify cobalt from accompanying impurities. The most difficult task in the purification of cobalt from impurities is the separation of cobalt from nickel, which is closest to it in chemical properties. A solution containing cations of these two metals is often treated with strong oxidizing agents - chlorine or sodium hypochlorite NaOCl; cobalt thus passes into the precipitate. The final purification (refining) of cobalt is carried out by electrolysis of its sulfate aqueous solution, to which boric acid H 3 BO 3 is usually added.
Physical and chemical properties
Cobalt is a hard metal that exists in two modifications. At temperatures from room temperature to 427°C, the alpha modification is stable (hexagonal crystal lattice with parameters a=0.2505 nm and c=0.4089 nm). Density 8.90 kg/dm 3 . At temperatures from 427°C to the melting point (1494°C), the beta modification of cobalt is stable (face-centered cubic lattice). The boiling point of cobalt is about 2960°C. Cobalt is a ferromagnet, (see Ferromagnetism (cm. FERROMAGNETISM)), Curie point (cm. CURIE POINT) 1121°C. Standard electrode potential Co 0 /Co 2+ -0.29 V.
In air, compact cobalt is stable; when heated above 300°C, it becomes covered with an oxide film (highly dispersed cobalt is pyrophoric (cm. PYROPHORIC METALS)). Cobalt does not interact with water vapor contained in the air, water, solutions of alkalis and carboxylic acids. Concentrated nitric acid passivates the surface of cobalt, just as it passivates the surface of iron.
Several oxides of cobalt are known. Cobalt (II) oxide CoO has basic properties. It exists in two polymorphs: an alpha form (cubic lattice), stable at temperatures from room temperature to 985°C, and a high-temperature beta form (also cubic lattice). CoO can be obtained either by heating cobalt hydroxorcarbonate Co(OH) 2 CoCO 3 in an inert atmosphere, or by careful reduction of Co 3 O 4 .
If cobalt nitrate Co (NO 3) 2, its hydroxide Co (OH) 2 or hydroxocarbonate is calcined in air at a temperature of about 700 ° C, then cobalt oxide Co 3 O 4 (CoO Co 2 O 3) is formed. This oxide is chemically similar to Fe 3 O 4 . Both of these oxides are relatively easily reduced by hydrogen to free metals:
Co 3 O 4 + 4H 2 \u003d 3Co + 4H 2 O.
When calcining Co (NO 3) 2, Co (OH) 2, etc. at 300 ° C, another cobalt oxide appears - Co 2 O 3. When an alkali solution is added to a cobalt (II) salt solution, a precipitate of Co (OH) 2 precipitates, which is easily oxidized. So, when heated in air at a temperature slightly above 100°C, Co(OH) 2 turns into CoOOH. If aqueous solutions of divalent cobalt salts are treated with alkali in the presence of strong oxidizing agents, then Co (OH) 3 is formed.
When heated, cobalt reacts with fluorine to form CoF 3 trifluoride. If COO or CoCO 3 is acted upon by gaseous HF, then another cobalt fluoride CoF 2 is formed. When heated, cobalt reacts with chlorine and bromine to form, respectively, CoCl 2 dichloride and CoBr 2 dibromide. By reacting metallic cobalt with gaseous HI at temperatures of 400-500°C, cobalt diiodide CoI 2 can be obtained. By fusing powders of cobalt and sulfur, silver-gray cobalt sulfide CoS (beta modification) can be prepared. If, however, a current of hydrogen sulfide H 2 S is passed through a solution of a cobalt (II) salt, then a black precipitate of cobalt sulfide CoS (alpha modification) precipitates:
CoSO 4 + H 2 S \u003d CoS + H 2 SO 4
When CoS is heated in an H 2 S atmosphere, Co 9 S 8 is formed with a cubic crystal lattice. Other cobalt sulfides are also known, including Co 2 S 3 , Co 3 S 4 and CoS 2 . With graphite, cobalt forms carbides Co 3 C and Co 2 C, with phosphorus - phosphides of the compositions CoP, Co 2 P, CoP 3. Cobalt also reacts with other non-metals, including nitrogen (nitrides Co 3 N and Co 2 N appear), selenium (cobalt selenides CoSe and CoSe 2 are obtained), silicon (silicides Co 2 Si, CoSi CoSi 2 are known) and boron ( among the known cobalt borides are Co 3 B, Co 2 B, CoB).
Metallic cobalt is able to absorb significant amounts of hydrogen without forming compounds of constant composition. Two stoichiometric cobalt hydrides CoH 2 and CoH were synthesized indirectly. Water-soluble cobalt salts are known - CoSO 4 sulfate, CoCl 2 chloride, Co(NO 3) 2 nitrate and others. Interestingly, dilute aqueous solutions of these salts have a pale pink color. If the listed salts (in the form of the corresponding crystalline hydrates) are dissolved in alcohol or acetone, then dark blue solutions appear. When water is added to these solutions, their color instantly turns into a pale pink.
Insoluble cobalt compounds include phosphate Co 3 (PO 4) 2, silicate Co 2 SiO 4. Cobalt, like nickel, is characterized by the formation of complex compounds. So, as ligands (cm. ligands) in the formation of complexes with cobalt, ammonia molecules NH 3 often act. Under the action of ammonia on solutions of cobalt(II) salts, ammine complexes of cobalt of red or pink color appear, containing cations of composition 2+. These complexes are rather unstable and are easily decomposed even by water.
Ammine complexes of trivalent cobalt, which can be obtained by the action of ammonia on solutions of cobalt salts in the presence of oxidizing agents, are much more stable. Thus, hexammine complexes with a 3+ cation are known (these yellow or brown complexes are called luteosalts), aquapentammine complexes of red or pink color with a 3+ cation (the so-called roseosalts). In some cases, the ligands around the cobalt atom can have different spatial arrangements, and then there are cis- and trans-isomers of the corresponding complexes.
Anions CN - , NO 2 - can also act as ligands in cobalt complexes. By reacting a mixture of hydrogen and CO with cobalt hydroxocarbonate at elevated pressure, as well as by reacting CO and powder of metallic cobalt under pressure, binuclear dicobalt octacarbonyl of the composition Co 2 (CO) 8 is obtained. When it is gently heated, carbonyl Co 4 (CO) 12 is formed. Carbonyl Co 2 (CO) 8 is used to obtain highly dispersed cobalt, which is used to apply cobalt coatings on various materials.
Application
The main share of the obtained cobalt is spent on the preparation of various alloys. Thus, the addition of cobalt makes it possible to increase the heat resistance of steel, improves its mechanical and other properties. Cobalt is a component of some hard alloys, from which high-speed tools (drills, drills) are made. Especially important are magnetic cobalt alloys (including the so-called magnetically soft and magnetically hard). Cobalt-based magnetic alloys are used in the manufacture of electric motor cores, they are used in transformers and other electrical devices. For the manufacture of magnetic recording heads, cobalt soft magnetic alloys are used. Cobalt hard magnetic alloys such as SmCo 5 , PrCo 5 , characterized by high magnetic energy, are used in modern instrumentation.
For the manufacture of permanent magnets, alloys containing 52% cobalt and 5-14% vanadium or chromium (the so-called wicalloys) are used. (cm. VIKALLOY)). Cobalt and some of its compounds serve as catalysts (cm. CATALYSTS). Cobalt compounds introduced into glasses during their melting provide a beautiful blue (cobalt) color to glass products. Cobalt compounds are used as pigments in many dyes.
Biological role
Cobalt is one of the trace elements (cm. MICROELEMENTS), that is, it is constantly present in the tissues of plants and animals. Some land plants and algae are able to accumulate cobalt. Entering the molecule of vitamin B 12 (cobalamin), cobalt is involved in the most important processes of the animal body - hematopoiesis, the functions of the nervous system and liver, and enzymatic reactions. Cobalt is involved in enzymatic processes of atmospheric nitrogen fixation by nodule bacteria. The body of an average person (body weight 70 kg) contains about 14 mg of cobalt. The daily requirement is 0.007-0.015 mg, daily intake with food is 0.005-1.8 mg. In ruminants, this need is much higher, for example, in dairy cows - up to 20 mg. Cobalt compounds are necessarily included in microfertilizers. However, an excess of cobalt is harmful to humans. MPC dust of cobalt in the air is 0.5 mg/m 3 , in drinking water the permissible content of cobalt salts is 0.01 mg/l. The toxic dose is 500 mg. Particularly toxic are the vapors of cobalt octacarbonyl Co 2 (CO) 8 .
Radionuclide cobalt-60
Of great practical importance is the artificially produced cobalt radionuclide 60 Co (half-life T 1/2 5.27 years). The gamma radiation emitted by this radionuclide has a sufficiently powerful penetrating ability, and "cobalt guns" - devices equipped with 60 Co, are widely used in flaw detection, for example, gas pipeline welds, in medicine for the treatment of oncological diseases and for other purposes. 60 Co is also used as a radionuclide label.
encyclopedic Dictionary. 2009 .
Synonyms:Scientific and technical encyclopedic dictionary
- (Cobaltum), Co, chemical element of group VIII of the periodic system, atomic number 27, atomic mass 58.9332; metal, mp 1494shC; ferromagnet, Curie point 1121shC. Cobalt is a component of magnetic, high-strength, hard and other alloys; ... ... Modern Encyclopedia
- (lat. Cobaltum) Co, a chemical element of group VIII of the periodic system, atomic number 27, atomic mass 58.9332. The name is from the German Kobold brownie, gnome. Silvery white metal with a reddish tint; density 8.9 g / cm³, mp 1494 .C; ... ... Big Encyclopedic Dictionary
Husband. a grayish metal, in various fossils, which, by appearance, are called: cobalt white, red, etc. Cobalt, containing cobalt, related to it. Cobalt flowers, arsenic cobalt red. Dahl's Explanatory Dictionary. IN AND. Far... ... Dahl's Explanatory Dictionary
Cobalt- (Cobaltum), Co, chemical element of group VIII of the periodic system, atomic number 27, atomic mass 58.9332; metal, mp 1494°C; ferromagnet, Curie point 1121°C. Cobalt is a component of magnetic, high-strength, hard and other alloys; ... ... Illustrated Encyclopedic Dictionary
Cobalt- (Co) hard silvery metal. It is used: for the production of special alloys, parts of turbojet aircraft engines, cutting tools, magnetic materials; when welding; in the ceramic and glass industry; in rural ... ... Russian encyclopedia of labor protection
COBALT- COBALT, Cobaltum (chemical sign Co), a shiny white metal with a reddish tint, belonging to the VIII group and the 4th row of the Mendeleev periodic system. In its typical compounds, K. is bivalent and trivalent, forming two series of salts: oxides ... ... Big Medical Encyclopedia
COBALT- chem. element, symbol Co (lat. Cobaltum), at. n. 27, at. m. 58.93; heavy silvery-white metal with a reddish tint, density 8900 kg/m3, tmelt = 1493 °C. K. refers to ferromagnets. Cobalt minerals are rare and do not form industrial ... ... Great Polytechnic Encyclopedia
Co (from German Kobold brownie, gnome * a. cobalt; n. Kobalt; f. cobalt; i. cobalto), chem. element of group VIII periodic. Mendeleev systems, at. n. 27, at. m. 58.9332. Natural K. consists of 2 stable isotopes 59Co (99.83%) and 57Co (0.17%) ... Geological Encyclopedia