Cobalt oxides chemical and physical properties of cobalt oxides chemical reference. Cobalt oxides chemical and physical properties of cobalt oxides chemical reference Finding in nature, obtaining

Cobalt oxides

COBALT OXIDES... Monoxide CoO - gray, brown or olive-green crystals with cubic. lattice ( a -form; a = 0.4258 nm, z = 4, spaces, group Fm3m); dense 6.47 g / cm 3. At 985 ° C turns. in b -modification similar in structure a -shaped, but less dense. T-pa Neel 290 K; at this temperature, a transition to tetragon is observed, a modification (at -180 ° C a = 0.42552 nm, c = 0.42058 nm); D H 0 transition 0.30 kJ / mol. T. pl. 1810 ° C; C 0 p 55.2 JDmol. TO); DH 0 sample - 239 kJ / mol; S 0 298 52.7 JDmol. TO); ur-tion of the temperature dependence of the dissociation pressure lgp (hPa) = 11.15-25200 / T (1000-1500 K). P-type semiconductor; the band gap is 0.65 eV.Virtually no sol. in water (3.1. 10 -4% by weight) and org. p-amateurs. Solution in alkali melts, with air access, in NH 3 solution. When loading. in air above 390 ° C transforms into Co 3 O 4. Easy to interact. with the miner, to-tami. Unlike NiO, it is not passivated upon calcination. Easily reduced to metal by the action of H2 (above 120 ° C) and CO (above 200 ° C). Forms non-stoichiometric with oxygen. phase.Get CoO thermal. decomposition of Co (OH) 2 or hydroxycarbonate Co in an inert atmosphere, reduction or thermal. decomposition of Co 3 O 4. CoO is used to obtain catalysts, ferrites, as a component of solid electrolytes, a pigment for ceramics, glass, and porcelain.Cobalt oxide (II, III) Co 3 O 4 - gray or black crystals with cubic. a spinel-type lattice (a = 0.8086 nm, z = 8, spaces, group Fd3w); dense 6.073 g / cm 3; C 0 p 122.8 JDmol. TO); D H 0 arr - 887 kJ / mol; S 0 298 102.9 JDmol. TO). T-ra Neel 40 K. With a load. above 900 ° Cdecomposes to CoO, ur-tion of the temperature dependence of the decomposition pressure logp (hPa) = 17.37-17700 / 7 (1033-1143 K).Not sol. in water and org. p-amateurs. Almost no interaction. with a miner. to-tami. Solution into the melt. alkalis. Forms non-stoichiometric with oxygen. phase. H 2 and CO are easily recovered. It is obtained by calcining hydroxides, hydroxocarbonate or Co nitrate in air at ~ 700 ° C. With 3 About 4 - the starting material for obtaining metallich. Co, CoO, catalysts, charge component for special ceramics, reagent for org. analysis.Sesquioxide Co 2 O 3 - gray, dark brown or black cryptocrystalline. in-in; the O 2 content in it is usually slightly less than stoichiometric. The structure is hexagonal (a = 0.464 nm, c = 0.567 nm, z = 2); D H 0 sample - 577 kJ / mol. Above ~ 300 ° C, it decomposes to Co 3 O 4. Virtually no sol. in water and org. p-amateurs. Reacts with difficulty with to-tami. It is obtained by heating Co hydroxides or nitrate at ~ 300 ° C. Stoichiometric Co 2 O 3, apparently, can be used. received thermal. decomposition. Co 2 O 3 - catalyst in org. synthesis, pigment for enamels and glazes, cathode material for electroplating. elements with non-aqueous solutions of electrolytes. It is used to obtain ferrites, as an adsorbent for gas chromatography.Cobalt (II) hydroxide Co (OH) 2 - blue ( a -form) or pink cryptocrystalline, or violet crystalline. ( b -form) in-in. a -Form [sometimes given for it f-lu ЗСо (ОН) 2. 2H 2 O] is metastable and with aging transforms into b -form. The structure of both modifications is hexagonal; for a : a = 0.309 nm, c = ~ 0.8 nm, for b : a = 0.3173nm, c = 0.4640nm, z = l, spaces, group P3ml, dense. 3.60 g / cm 3; D H 0 ref - 540 kJ / mol; S 0 298 83 JDmol. TO). Virtually no sol. in water (2.10 -4% by weight) and org. p-amateurs. Solution in solution NH 3. Reacts easily with to-tami, with conc. solutions of alkalis forms hydroxocobaltates, for example. Na 4. Freshly precipitated Co (OH) 2 is easily oxidized in air. When loading. in air at 110 ° C turns. at UNS. Without air access, it dehydrates above 150 ° C ( b - the form does not completely release water even at 300 ° C). Received by the action of solutions of NaOH or NH 3 on solutions of salts of Co. Used to obtain Co salts and catalysts.Cobalt (III) hydroxide Co (OH) 3- dark brown cryptocrystalline. in-in; the structure is similar to Co 2 O 3; dense 4.29 g / cm 3. The water content is usually slightly less than stoichiometric; may contain an excess of active oxygen due to the admixture of hydroxide CoO 2 nH 2 O, not obtained - in a pure state; D H 0 ref - 725.5 kJ / mol; S 0 298 100 J / (mol. K). At ~ 100 ° C, it partially dehydrates with the formation of COOH. Decomposes in the light. Virtually no sol. in water (3. 10 -4% by weight), not sol. in org. p-amateurs. It reacts with difficulty with HNO 3 and H 2 SO 4 (with the release of O 2), easier - with hydrochloric acid (with the release of Cl 2), with HF and with H 2 SO 3. Does not react with alkali solutions. Hygroscopic. Co (OH) 3 is obtained by the action of oxidants (Cl 2, NaOCl, H 2 O 2) on solutions of Co salts in the presence. alkalis. Co (OH) 3 - interm. product upon receipt of Co 3 O 4 and salts of Co (III).Cobalt (III) hydroxoxide CoOOH - black crystals; known in two modifications - trigonal (rhombohedral.) with dense. 4.72 g / cm 3 (a = 0.2851 nm, c = 1.3150 nm, z = 3, spaces, group R3m) and a rhombic diaspora formed at high t-pax and pressures (a = 0.4353 nm, b = 0.9402 nm, c = 0.2840 nm, z = 4, spaces, Pbpt group); DH 0 sample - 435 kJ / mol. At 300 ° C, it dehydrates with the loss of some oxygen. Not sol. in water. Reacts with hydrochloric acid to release Cl 2; with HNO 3 and H 2 SO 4 interaction. hardly. P-rye and NH 3 have no effect on it. Obtained by heating Co hydroxides at ~ 100 ° C in air, by the action of H 2 O 2 on a Co (OH) 2 suspension at heating. in the presence. alkali Reagent for obtaining catalysts, pigments, interm. product upon receipt of Co 3 O 4.Cobalt oxides are toxic

Cobalt is a rather rare mineral, which in its pure form is a heavy metal with a silvery color and a pinkish tint. At the same time, the production and use of cobalt oxides was noted back in the days of Ancient Egypt and Babylon, where Co + O was used to make blue enamels. Cobalt oxide (or oxide) is an inorganic compound in the form of water-insoluble crystals.

Formula for obtaining Co + O

Cobalt oxide can be obtained in several ways:

1. Oxidize the metal in air at a temperature of 300 о С (2Сo + O 2 = 2CoO).
2. Oxidize octacarbonyl adicobalt at a temperature of 250-300 о С (2Со (Со) 8 + О 2 = 2СоО + 8СО 2).
3. Decompose cobalt sulfate at t = 600-700 o C (2CoSO 4 = 2CoO + 2CO 2 + O 2).
4. Decompose cobalt hydroxide in vacuum at t = 170 о С (Co (OH) 2 = CoO + H 2 O).
5. Decompose cobalt oxide when heated to t = 905-925 о С (2Со 3 О 4 = 6СоО + О 2).

Cobalt oxide according to GOST 18671-73 will contain the following elements:

Cobalt oxide: properties

In addition to insolubility in water (PR = 14.37), among the main physical properties of this inorganic compound, it is worth highlighting its belonging to the space group F m3m, as well as the transition of cobalt oxide to the β-modification at t = 985 o C.

Concerning chemical properties, then, as noted above, when heated, CoO is oxidized by oxygen and is soluble in hot alkalis and dilute acids. In addition, cobalt oxide can be reduced with hydrogen, it can be a starting element for obtaining a complex oxide (+ Al2O 3) or cobalt silicate (+ SiO 2).

Cobalt oxide applications

Today, this compound still acts as a colorant: in particular, it is used by the glass industry to obtain products of various shades. Cobalt oxide is also in demand by enterprises from the field of electrical engineering, where CoO participates in the creation of negative electrodes and capacitors. Finally, the chemical industry - here cobalt oxide often plays the role of a catalyst for all kinds of chemical processes (for example, Co 3 O 4 or CoF 3 is a fluorinating agent).

In general, cobalt is an alloying element, therefore it is often involved in the creation of special alloys. Its presence makes the material heat-resistant and heat-resistant. Another use of cobalt oxide is as a fertilizer and feed additive in agriculture and animal husbandry.

The storage of cobalt oxide is carried out in accordance with strict rules: a multi-layer paper bag, placed in another polyethylene or linen-jute-kenaf bag and, finally, in a metal container. This is explained by the fact that this inorganic compound is classified as a substance of the second hazard class (the substance is toxic).

are crystalline powders from black to grayish-green, inorganic compounds. Insoluble in water and other solvents.

Cobalt (II) oxide CoO. It is obtained by heating metallic cobalt in air or by calcining Co (OH) 2 or CoCO 3 without access to air. Dark green (almost black) crystals. Also known as cobalt oxide. It dissolves in dilute acids, slowly dissolves in hot alkalis. Oxidized by atmospheric oxygen when heated. Reduced with hydrogen. Density: 6.45 g / cm³. Melting point 1810 ° C.
Cobalt (II, III) oxide Co 3 O 4. It is obtained by heating CoO kept in air or by calcining Co 2 O 3. Gray-black crystals. Also known as cobalt oxide. It is a paramagnetic. Decomposes on heating. It dissolves slowly in concentrated acids. When fused with alkalis, it is oxidized by oxygen. Reduced with hydrogen. Density: 6.073 g / cm³. Melting point 900 ° C (decomposes).
Cobalt (III) oxide Co 2 O 3. It turns out by the oxidation of cobalt oxides with peroxides, bromine, potassium permanganate or precipitation with alkali from Co (III) salts. Black crystals. Decomposes in steps when heated. Oxidizes hydrochloric acid. Density: 5.18 g / cm³. Melting point 300 ° C (decomposes).

Cobalt Oxide Application:
Cobalt oxide is often used in the glass industry. It is a stable and intense colorant (pigment) for glass products. Coloring with cobalt compounds is very constant and does not depend on the cooking mode. When using cobalt compounds in combination with other dyes, glasses with different shades can be obtained.
IN chemical industry it is used as a catalyst for various chemical processes.
It is also used in the electrical industry for the production of capacitors, varistors and negative electrodes in batteries.

Physical and chemical indicators of cobalt oxide GOST 18671-73:

Indicator name	Rate for the variety
	top grade	first grade
Mass fraction of cobalt (Co),%, not less	72,5	71
Mass fraction of iron (Fe),%, no more	0,05	0,05
Mass fraction of silicon (Si),%, no more	0,02	0,03
Mass fraction of cadmium (Cd),%, no more	0,006	0,006
Mass fraction of calcium (Ca),%, no more	0,04	0,06
Mass fraction of manganese (Mn),%, no more	0,01	0,015
Mass fraction of copper (Cu),%, no more	0,01	0,02
Mass fraction of arsenic (As),%, no more	0,002	0,002
Mass fraction of sulfur (S),%, no more	0,01	0,015
Mass fraction of antimony (Sb),%, no more	0,006	0,006
Mass fraction of lead (Pb),%, no more	0,002	0,002
Mass fraction of zinc (Zn),%, no more	0,03	0,03
Mass fraction of nickel (Ni),%, no more	0,2	0,2

Cobalt oxide safety requirement.
Cobalt oxide is classified as a hazard class 2 substance. Has a general toxic and irritating effect, affects the upper respiratory tract, affects the cardiovascular system, causes bronchitis, pneumosclerosis, hypotension, dermatitis. It accumulates in the body.
The concentration of cobalt oxide in the air of the working area in the form of an aerosol should not exceed the MPC - 0.5 mg / m³.
Cobalt oxide is not subject to neutralization and destruction. The spilled product after dry to subsequent wet cleaning is disposed of on technological processes receiving or consuming cobalt oxide.
In the air and waste water in the presence of other substances or factors, cobalt oxide does not form toxic substances. Cobalt oxide is not flammable, fire and explosion proof.
All persons involved in the work and analysis of cobalt oxide must be provided with special clothing, collective and personal protective equipment. The means of collective protection are the complex mechanization of labor, the availability of ventilation and exhaust ventilation and systematic monitoring of the state of the air environment.

Packing, transportation and storage.
Cobalt oxide is packed in three to five-layer paper bags, which are then put into polyethylene bags or linen-jute-kenaf bags with a base of rayon threads, and then placed in universal metal containers. It is allowed to place bags in metal barrels or wooden barrels, or steel drums with a batch of less than 3 tons. Polyethylene bags are sealed, and paper linen-jute-kenaf bags are sewn up. The net weight of the bag should not exceed 50 kg.
Cobalt oxide is transported by any type of transport, except for air transport, in accordance with the rules for the carriage of goods in force for this type of transport.
Cobalt oxide should be stored in the manufacturer's packaging in closed warehouses, protecting the product from moisture and excluding contact with vapors of acids and alkalis.
The guaranteed shelf life of the product is 12 months from the date of manufacture.

The name "cobalt" comes from the German word Kobold, which means "dwarf guarding the treasures" (mountain spirit or evil spirits), or from the Greek word kobalo, which means "talented emperor". The term kobelt was first mentioned in Agricola's Mining and Metallurgy.
Archaeologists have found a cobalt blue-stained glass necklace that was made 2500 BC. Cobalt-containing dyes were used in China between 907 and 618 BC. Metallic cobalt (contaminated) was first obtained in 1735 by the Swedish chemist G. Brandt.

Being in nature, getting:

Spectral analysis revealed the presence of cobalt in the atmosphere of the Sun and various stars. In nature, there are two stable isotopes: 59 Co and 57 Co. Content in the earth's crust is 4 * 10 -3%. Cobalt is rarely found in the form of nuggets, but its compounds are very common. The most important minerals: carrolite CuCo 2 S 4; linneite Co 3 S 4; cobaltin CoAsS; skutterudite CoAs 3; schmaltinchloanthin (Co, Ni, Fe) As 3; safflorite (Co, Fe) As 2.
Cobalt is found in small amounts in the tissues of animals and plants, in particular, it is part of vitamin B 12 (C 63 H 88 O 14 N 14 PCo).
Metallic cobalt is obtained by reduction of oxides, salts, complex compounds (Cl 2, CO 3) with hydrogen, carbon, carbon monoxide or methane (when heated), aluminum or silicon-thermal reduction of cobalt oxides, thermal decomposition of carbonyls Co 2 (CO) 8, Co 4 (CO) 12 and electrolysis of aqueous solutions of salts CoSO 4 * 7H 2 O or (NH 4) 2 SO 4 * CoSO 4 * 6H 2 O.

Physical properties:

In a compact state, cobalt is a silvery-white metal with a pinkish sheen with a density of 8.83 g / cm 3, so pl. 1492 °, etc. kip. 3185 °. Cobalt is harder than iron (5.5 on the Mohs scale), more fragile than steel, has ferromagnetic properties (which disappear at temperatures above 1150 °, and a paramagnetic modification is formed), viscous and difficult to forge. Cobalt metal is known in two crystalline modifications: a-Co - with a dense hexagonal structure and b-Co - with a cubic face-centered crystal lattice. Cobalt pyrophoric is a black powder that oxidizes in air at ordinary temperatures, while heating up to white heat. Colloidal cobalt has a golden brown color.

Chemical properties:

At normal temperatures, metallic cobalt in a compact state is resistant to dry and humid air, water, strong alkalis and dilute solutions of organic acids. At temperatures above 300 ° C, it becomes covered with a film of oxides. Cobalt-magnesium alloy vigorously decomposes water in the cold.
Powdered cobalt interacts when heated with halogens, sulfur, phosphorus, arsenic, antimony, carbon, silicon, boron, but does not react with nitrogen:
Metallic cobalt slowly dissolves in dilute hydrochloric and sulfuric acids and quickly in dilute nitric acids, since the normal potential of the Co / Co 2+ system is -0.277V:
8Co + 20HNO 3 + (n-10) H 2 O = 8Co (NO 3) 2 * nH 2 O + 2NO + N 2
Under the influence of fuming HNO 3 in the cold, cobalt is passivated. Hydrofluoric acid and aqua regia react with cobalt in the cold. Molten potassium hydroxide (550 ° C) also dissolves metallic cobalt.

The most important connections:

In compounds, cobalt exhibits oxidation states of +2 and +3.
Cobalt (II) oxide, CoO - amphoteric oxide, displaces ammonia from warm solutions of ammonium salts; when fusing with an excess of alkali, cobaltites of a bright blue color are formed, in solutions - hydroxocobaltates.
Cobalt (II) hydroxide Co (OH) 2, - exists in two modifications, slightly soluble in water, soluble in warm concentrated solutions of alkalis, mineral acids and most organic acids.
Co (OH) 2 catalyzes the oxidation of sodium sulfite with atmospheric oxygen.
Cobalt (II) salts- usually obtained by treating CoO or Co (OH) 2 with various acids. Salts of strong acids are mostly soluble, solutions have an acidic reaction due to hydrolysis. Diluted salt solutions contain a pink 2+ cation. The color of crystalline hydrates is the same, anhydrous salts are blue.
Complex compounds of cobalt (II) are rather unstable and easily oxidized to compounds of cobalt (III).
Carbonyls... Known mono- and polynuclear carbonyl compounds of cobalt:
2CoI 2 + 8CO + 4Cu = Co 2 (CO) 8 + 4CuI
Cobalt dihydride(dark gray crystals) stable under a layer of ether below 5 ° C:
CoCl 2 + 2C 6 H 5 MgBr + 2H 2 = CoH 2 + 2C 6 H 6 + MgBr 2 + MgCl 2
Cobalt (III) compounds: numerous complex compounds of cobalt (III) are known: cationic (Cl 3), anionic (K 3, neutral.
For complexes with different ligands, cis-trans isomerism is possible.
K 3 - hexanitrite-cobalt (III) at potassium, insoluble, yellow precipitate, qualitative reaction to potassium salts (the reagent is a soluble salt of hexanitrite-cobalt (III) at sodium).
Cobalt oxide (II-III), Co 3 O 4 is a strong oxidizing agent, dissolves in acids with the evolution of oxygen:
2Co 3 O 4 + 6H 2 SO 4 = 6CoSO 4 + O 2 + 6H 2 O.

Application:

Component of solid heat-resistant, magnetic, corrosion-resistant and other alloys and coatings for the production of cobalt-containing catalysts. Radioactive isotope 60 Co (T 1/2 = 5.24s) - source g-radiation in engineering and medicine.
Since antiquity, the use of oxides CoO and Co 3 O 4 has been known in the manufacture of blue enamels and for coloring molten glass in blue. The ability of cobalt oxides to form solid solutions (colored in blue, green, pink and other colors) with oxides of various metals led to their use in the ceramic and glass industries.

A.V. Batrakova
KhF Tyumen State University

Sources: 1. Ripan R., Chetyanu I. Inorganic chemistry, vol. 2 / per. from Romanian - Moscow: Mir Publishing House, 1972 .-- 872 p.
2. Chemical encyclopedic dictionary / ed. I.L. Knunyants. - M .: Great Russian Encyclopedia, 2003 .-- 792 p.

Cobalt oxide (Cobalt oxide)- inorganic compound, cobalt metal oxide.

Physiochemical properties.

Chemical formula Co 3 O 4. Cobalt oxide is a black to grayish-green crystalline powder. Insoluble in water and other solvents. It dissolves in dilute acids, slowly dissolves in hot alkalis. Oxidized by atmospheric oxygen when heated. Reduced with hydrogen. Density: 6.45 g / cm 3. At 1300 ° C, it dissociates with the formation of 4CoO × Co 2 O 3, and on further heating transforms into CoO.

Application.

Cobalt oxide is used as a catalyst (accelerator) for various high-temperature chemical processes, in the production of glass, batteries, for alloying steels, as an adsorbent for gas chromatography

In some cases, cobalt oxide is used in metallurgy as a source of cobalt. Metallurgy is the largest consumer of cobalt (about 40-75%). However, in addition to cobalt oxide in metallurgy, cobalt-containing ores, scrap metal with cobalt content, and various chemical compounds of cobalt are used. It depends on the availability of raw materials and the specifics of metallurgical technology.

There are two main areas of use of cobalt in metallurgy: the production of permanent magnets and the production of alloy steels.

Cobalt has some properties similar to iron and is a ferromagnet. Small additions of cobalt to the compositions of steels for permanent magnets significantly increase their magnetic properties. In addition to cobalt, nickel and aluminum are added to the permanent magnets.

Cobalt alloying is performed for high-speed steels with increased cutting properties. Designed for tough cutting and impact roughing. Also, such steels are used for the manufacture of ammunition equipment with special properties. In addition to cobalt, such steels contain other alloying additives: tungsten, tantalum, titanium.

In order for the battery voltage to be large enough, cobalt oxides are used as the active material of the positive electrode, into which lithium ions are also reversibly incorporated.

The electrolyte is a solution of a lithium salt in a non-aqueous aprotic solvent. During the discharge, lithium leaves the carbon material (at the anode) and is incorporated into cobalt oxide (at the cathode), while the valence of cobalt decreases. When charged, lithium ions are extracted back and the process goes in the opposite direction. Literated cobalt oxide has a potential of about 4 V relative to the lithium electrode, so the operating voltage of a Li-ion battery has a characteristic value of 3 V or higher. Batteries have high specific energy, long service life and are capable of operating at low temperatures. Due to their high specific energy, they are used in cell phones, laptops and other portable devices.

Cobalt oxide is not used as a pigment for food products due to the health risks of high concentrations of cobalt.

Cobalt oxide is a part of paints for professional artists in all types of painting. Gives the paint a blue color. These paints do not fade for hundreds of years and are very expensive.

Cobalt oxide is included in the underglaze paint for ceramics (i.e. before the glaze of the product). This is its use due to the resistance of the pigment to high temperatures.

Cobalt oxide is used by glass factories to color glass in various shades of blue. The additive in small quantities is blue glass, and in large quantities it is violet-blue with a reddish tint. When using cobalt compounds in combination with other dyes, glasses with different shades can be obtained. Coloring with cobalt compounds is very constant and does not depend on the cooking mode.

Nitrogen oxides NO, NO 2, N 2 O 3, N 2 O 4 - poisonous gases for the environment and human health. Their permissible content is regulated by sanitary norms and rules for the protection of the environment. Nitrogen oxides are present in all fuel combustion products. However, with a high-quality fuel combustion mode, the presence of fuel oxides in flue gases is minimal. These flue gases contain traces of nitrogen oxides. For example, the flue gases of industrial hot water boilers, when operating in passport modes, do not contain nitrogen oxides (only traces). The same boilers in emergency modes associated with breakdowns of boiler elements (burners, heat exchangers, lining leaks, etc.) produce flue gases with a high content of nitrogen oxides. The formation of a large amount of nitrogen oxides in the flue gases indicates a low temperature in the combustion zone. This is due to the lack or excess of air entering the combustion zone.

There are technologies in which it is not possible or desirable to completely oxidize the fuel with atmospheric oxygen. Since the excess or lack of this is associated with the sequence of chemical transformations. And it can affect the marriage of finished products. For example, a separate stage (period) in metallurgical smelting.

Cobalt oxide is used in the catalytic method of cleaning flue gases from nitrogen oxides. At temperatures above 620 ° C, all higher nitrogen oxides dissociate to NO, and at 900 - 1000 ° C, NO dissociation into nitrogen (N 2) and oxygen (O 2) is possible with a heat release of 181 kJ / mol. Since the reaction is slow, a catalyst is used to accelerate it - cobalt oxide.

Cobalt oxide is a part of materials for the manufacture of thermistors with a range of operation at temperatures from minus 90 to plus 1000 ° C. Such resistors satisfy a number of special requirements, in particular, they have purely electronic conductivity and chemical stability in the operating temperature range.

Cobalt oxide is a nonstoichiometric oxide, in which different valence metal ions are formed, which ensures the appearance of semiconducting properties.

Receiving.

Cobalt oxide is produced by oxidizing metallic cobalt by heating.