trioxochromium
Chromium(III) oxide
CAS: 1308-38-9
Molecular Formula: Cr2O3
trioxochromium - Names and Identifiers
trioxochromium - Physico-chemical Properties
| Molecular Formula | Cr2O3 |
| Molar Mass | 151.99 |
| Density | 5.21 |
| Melting Point | 2435 °C |
| Boling Point | 4000 °C |
| Flash Point | 3000°C |
| Water Solubility | Insoluble |
| Solubility | Insoluble in all solvents |
| Appearance | Green crystallization |
| Specific Gravity | 5.22 |
| Color | Pale to dark green |
| Exposure Limit | NIOSH: IDLH 25 mg/m3; TWA 0.5 mg/m3 |
| Merck | 14,2234 |
| Storage Condition | Room Temperature |
| Stability | Stable. |
| Sensitive | Easily absorbing moisture |
| Refractive Index | 2.551 |
| MDL | MFCD00010949 |
| Physical and Chemical Properties | Hexagonal or amorphous dark green powder. Metallic luster. cubic or amorphous green powder. There are usually two shades: light olive green and dark olive green. Metal color. The relative density was 5.21. Melting point 2266 °c. Boiling point 4000 °c. It has excellent heat resistance, can resist temperature of 1000 ° C. Without discoloration, and is also excellent in acid resistance and alkali resistance. Insoluble in water, insoluble in acid, soluble in hot alkali metal bromate solution. It is extremely stable to light, atmosphere, sulfur dioxide, hydrogen sulfide and other corrosive gases. It has a high hiding power, but the tinting power is not better than that of Phthalocyanine Green, the color tone is not bright enough, the particle size is hard, and the paint gloss is slightly poor. Magnetic. Toxic. |
| Use | Mainly used in special steel smelting tapping mouth, slide mouth and large incinerator can be used for ceramic and enamel coloring, rubber coloring, preparation of high temperature resistant coatings, art pigments, ink for the preparation of printed notes and securities. The color of chromium oxide green is similar to that of plant chlorophyll, which can be used in camouflage paint and can be difficult to distinguish in infrared photography. Also a large number of used in metallurgy, production of refractory materials, grinding powder. It can also be used as a catalyst for organic synthesis and is a high-grade green pigment. |
trioxochromium - Risk and Safety
| Safety Description | 24/25 - Avoid contact with skin and eyes. |
| WGK Germany | - |
| RTECS | GB6475000 |
| TSCA | Yes |
| HS Code | 28199090 |
trioxochromium - Upstream Downstream Industry
| Raw Materials | Chromium(VI) oxide |
trioxochromium - Nature
Open Data Verified Data
light to dark green fine six-square crystal or powder. Metallic luster. Melting point about 2435 °c; Boiling point about 3000 °c I; d25 5.22. It turned brown by heating and green after cooling. Insoluble in water, ethanol, acetone, slightly soluble in acid, alkali and hot potassium bromate solution.
Last Update：2024-01-02 23:10:35
trioxochromium - Preparation Method
Open Data Verified Data
It is prepared by mixing potassium dichromate with sulfur or ammonium chloride and reducing roasting. It can also be prepared by heating and decomposing chromic anhydride or ammonium dichromate or chromium hydroxide.
Last Update：2022-01-01 09:01:39
trioxochromium - Introduction
Soluble in heated potassium bromate solution, slightly soluble in acids and alkalis, almost insoluble in water, ethanol and acetone. There is irritation.. It has a metallic luster. It is extremely stable to light, atmosphere, high temperature and corrosive gases such as sulfur dioxide and hydrogen sulfide. It has high hiding power and is magnetic. It turns brown when hot, and turns green when cold. Crystals are extremely hard. The property is extremely stable, and there is no change even when hydrogen is introduced under red heat. It's irritating.
Last Update：2022-10-16 17:13:11
trioxochromium - Use
Open Data Verified Data
It is used as a spectral analysis reagent, organic synthesis catalyst, ceramic glaze color raw material, and the manufacture of chromium alloy and chromium salt.
Last Update：2022-01-01 09:01:40
trioxochromium - Reference Information
| NIST chemical information | Information provided by: webbook.nist.gov (external link) |
| EPA chemical information | Information provided by: ofmpub.epa.gov (external link) |
| Overview | Chromium trioxide, also known as chromium oxide, chromium oxide green, chromium green, is a dark green crystalline powder with metallic luster, belongs to the hexagonal crystal system or the tripartite crystal system, and is the same crystal form as α-alumina. Chemical formula Cr2O3, molecular weight 151.99, relative density 5.21 (21 ℃), Mohs hardness 9, harder than Shi Ying and steel, melting point 2266±25 ℃, boiling point above 3000 ℃, chemical properties are extremely stable. It is magnetic, insoluble in water and ethanol, and resistant to both acid and alkali. Even in the red hot state, hydrogen is hardly reduced. In addition, it is difficult to react with sulfur and hydrogen sulfide. Chromium oxide green burned at high temperature is inert to acid and alkali, but it can be eutectic with acidic flux to convert into soluble chromium (III) salt. When heated with bromate alkali metal brine solution, it reacts and dissolves, and can be dissolved in hot potassium bromate solution. The chemical reaction equation is: 5Cr2O3 6 BrO3- 2H2O → 5 Cr2O72- 4H 3Br2 |
| application | chromium trioxide hydrate, commonly known as "water chrome green", is a purple amorphous crystal or blue gray green gel. Chromium trioxide can be used as a green pigment in printing inks and coatings. In addition, as a colorant, it has a wide range of uses in glass, ceramic tiles, ceramic utensils, etc., and can also use hard properties as greasy grinding materials such as green oil. Grinding the bottom plate and surface polishing during chrome and nickel plating. Chromium trioxide can also be made into chromium magnesium or magnesium chromium refractory bricks, and can be used as a metal chromium raw material. The most commonly used green pigment in enamel production is chromium trioxide. Its color can be from bright green to dark green. It has excellent light resistance, heat resistance, chemical corrosion resistance and other properties, high covering power, but dark color. It can be separately ground and added to the color base glaze to produce bean green color glaze, the amount of which is 3% ~ 5% of the glaze block; it can also be made with oxides or compounds such as aluminum, zinc, calcium, etc. at high temperatures Green pigments of different tones. |
| preparation of chromium trioxide by sodium dichromate | Cr2O3 is the main raw material for the production of metallic chromium. Cr2O3 is produced from chromite by chemical metallurgical method. First, chromite is oxidized and roasted to obtain sodium chromate (Na2CrO4) dissolved in water, and the trivalent chromium in the chromium ore is oxidized to hexavalent chromium. After water immersion, sodium chromate solution can be obtained, and chromium trioxide can be obtained by sodium dichromate method and chromium hydroxide method. The method of reducing sodium dichromate with ammonium chloride to prepare chromium trioxide. Sodium dichromate and ammonium chloride are mixed according to the calculated ingredient ratio (practice has proved that when the dosage of ammonium chloride is about 140% of the theoretical quantity, the conversion rate can reach 95-96%), and then they are placed in a flame-isolated reverberatory furnace for reduction. The chemical reaction formula is: Na2Cr2O7 + 2NH4Cl = Cr2O3 + 2NaCl + N2 + 4H2O After the reaction is over, the furnace charge is put into a washing tank with a stirrer and washed with hot water for several times, to remove sodium chloride. Then use a filter press to filter to obtain a paste-like chromium trioxide filter cake containing 30-35% moisture. After drying (temperature 300 ℃), it is calcined at high temperature, cooled and crushed, and is the finished product. The finished product contains Cr2O3(97%-98%). In addition to reducing sodium dichromate with NH4Cl to prepare Cr2O3, Cr2O3 can also be prepared by reducing Na2Cr2O7 such as sulfur and charcoal. The chemical reaction formula is: Na2Cr2O7 + S = Na2SO4 + Cr2O3 Na2Cr2O7 + 2C = Na2CO3 + CO + Cr2O3 |
| toxicity | the maximum allowable concentration is 1 mg/m3. For others, see chromic anhydride. |
| Uses | Used for smelting metal chromium, chromium carbide, polishing paste and paint pigments, and also used as colorants for enamel, glass, ceramics and catalysts for organic synthesis Used as catalysts and analytical reagents It can be used for coloring ceramics and enamels, rubber coloring, preparation of high temperature resistant coatings, and pigments for fine arts, ink for the preparation of printed banknotes and securities. The color of chromium oxide green is similar to the chlorophyll of plants. It can be used in camouflage paint, which can make it difficult to distinguish in infrared photography. It is also widely used in metallurgy, making refractory materials and grinding powder. It can also be used as an organic synthesis catalyst and is an advanced green pigment. lead chrome green is the main coloring pigment in the coating industry, and most green paints are prepared with this pigment. In addition, it is also used for paint and plastics. Its application range is very similar to lead chrome yellow. Because the composition contains chrome yellow, pay attention to its lead toxicity when applying. Lead chrome green contains iron blue and the oxidant lead chromate, so when the dust encounters Mars, there is a possibility of spontaneous combustion. Do not be careless when drying or crushing. After burning, lead-chromium green completely loses the characteristics of green pigment and turns into a dark brown-yellow substance. In addition, when making nitrocellulose paint, the rolling process does not directly use lead-chrome green rolling, but uses lead-chrome green slurping and then mixing in to prevent burning during rolling. Mainly used for smelting metal chromium and chromium carbide. Used as a glaze for enamels and ceramics. Colorants for artificial leather, building materials, etc. Special ink for manufacturing sun-resistant coatings, abrasive materials, green polishing paste and printing banknotes. Used as a catalyst for organic synthesis. It is a high-grade green pigment. Used for smelting metal chromium, chromium carbide, polishing paste and paint pigments; also used as enamel, glass, organic and inorganic reaction catalysts, refractive materials, colored glass, abrasives. Mainly used in special steel smelting tapping ports, sliding plate ports and large incinerators |
| production method | reduction method mixes 99.5% potassium dichromate and 98% sulfur in a weight ratio of 7:l and then roasts to generate chromium oxide and potassium sulfate. After the reaction, the charge is wet ground, then put into the washing tank with a stirrer and washed with hot water, and the chromium oxide is filtered out with a filter press to obtain a paste filter cake with a water content of 30% ~ 35%. The filter cake is dried at 300 ℃, cooled and crushed to produce a chromium oxide green product. Its K2Cr2O7 + S→CrO3 + K2SO4 washing solution contains a large amount of soluble salts such as potassium sulfate, chromium sulfate and hexavalent chromium. Hydrogen sulfide can reduce hexavalent chromium to generate chromium hydroxide precipitate, which is separated by filtration. Hydrochloric acid is added to the filtrate, and the solution is concentrated and crystallized to produce potassium chloride by-product. The sulfur dioxide and sulfur trioxide gas released during roasting are absorbed with dilute ammonia water to produce ammonium sulfate by-product. 99.5% chromic anhydride was calcined at about 1400 ℃ for l ~ 1.5h by thermal decomposition to generate chromium oxide. After cooling, it is ground with a high-speed crusher to produce a chrome oxide green product. Its 4CrO3 → 2Cr2O3 3O2 thermal decomposition chromium hydroxide method adds sodium sulfide solution to the sodium chromate hot solution for reaction to generate chromium hydroxide. After filtration, the obtained chromium hydroxide filter cake is washed and centrifuged and dehydrated. Roast at a temperature of about 1400°C to generate chromium trioxide. The charge is washed, dried, and crushed to obtain a finished chromium oxide product. Its 8Na2CrO4 + 6Na2S + 2H2O → 8Cr(OH)3+3Na2S2O3+22 NaOH2Cr(OH)3 → Cr2O3 + 3H2O to separate the lye obtained by chromium hydroxide, and sodium bicarbonate and sodium thiosulfate can be recovered after carbonization by carbon dioxide. The chromium trioxide produced by this method is dark in color and should not be used as a pigment. It is mainly used for smelting metal chromium and making polishing paste. Since lead-chrome green is a color-matching pigment, the production process is mainly the combination of yellow and blue pigments. There are three production methods. The coprecipitation method of lead-cadmium yellow with iron blue or phthalocyanine blue or silicui blue. The pigment produced by this method has a better color, and the paint is not easy to float and delaminate. Iron blue should be made in advance, rinsed to slightly acidic, containing only a small amount of soluble salt, added to the lead salt solution, and then added to the mixture of lead salt solution and iron blue according to the method of making lead chrome yellow Sodium dichromate and other solutions can be rinsed, filtered, dried and crushed in the future. The production process and equipment are roughly similar to the process of producing lead chrome yellow. Iron blue is not alkali resistant, pay attention to remain slightly acidic or neutral during the reaction. The ratio of yellow and blue pigments depends on the required lead-chrome green color. Phthalocyanine blue has good acid and alkali resistance, and can be directly reacted with chrome yellow raw materials to co-precipitate. The selected phthalocyanine blue pigment should be fine particles, added to lead salt solution after beating with water, and the rest of the operation is the same as that of iron blue. Silicure Blue can be dissolved in water. After being heated and dissolved, it can be added to the lead salt solution, and then the chromate solution is added dropwise to generate a mixture of chrome yellow and dye solution, and then the barium chloride solution is added dropwise to make the dye Complete precipitation into insoluble barium salt, the end point control can be done on the filter paper for infiltration circle test, and no blue dye should be infiltrated at the end point. The rest of the washing, filtering, drying, and crushing processes are the same as the above varieties. The lead chrome yellow pigment water slurry is mixed with iron blue or phthalocyanine blue pigment water slurry in a certain proportion, and then filtered and dried. Lead chrome yellow and iron blue are prepared separately, washed to remove water-soluble salt, and then color according to the color requirements of the finished product. In order to prevent floating toner from delamination, a small amount of surfactant or dispersant can be added to make the mixture uniform. Dry color matching. This is the simplest method, the color matching is very flexible, but lead chrome yellow and blue pigments such as iron blue and phthalocyanine blue should have a certain fineness to mix evenly, and it is generally not suitable to be crushed after mixing, which can avoid the possibility of spontaneous combustion. Silicure Blue is water-soluble and cannot be directly used for dry spelling. There are three production methods. reduction method. Reaction equation: K2Cr2O7 + S→Cr2O3 + K2SO4 operation method: potassium dichromate powder with 99.5% content and 98% sulfur powder with 7:1 weight ratio are mixed and calcined (600~700 ℃,3~5h) to generate chromium oxide and potassium sulfate. After the reaction, the charge is wet ground, and then put into a washing tank with a stirrer and washed with hot water to remove soluble sulfate. Chromium oxide is filtered out by a filter press to obtain a paste filter cake with a water content of 30% ~ 35%. The filter cake is dried at 300 ℃, cooled and crushed to obtain a green chromium oxide product. Thermal decomposition of chromic anhydride. Reaction equation: 4CrO3 → 2Cr2O3+3O2 Operation method: 99.5% chromic anhydride is calcined at about 1400 ℃ for 1~1.5h to generate chromium oxide. After cooling, it is ground with a high-speed crusher to produce a chrome oxide green product. Thermal decomposition of chromium hydroxide. Reaction equation: 8NaCrO4 + 6Na2S + 23H2O → 8Cr(OH)3+3Na2S2o3 + 22NaOH 2Cr(OH)3 → Cr2O3 + 3H2O Operation method: Add sodium sulfide solution into sodium chromate solution for reaction to generate chromium hydroxide, filter to obtain chromium hydroxide filter cake, after washing and drying, obtain chromium hydroxide. The chromium hydroxide dry powder was mixed with 5% sodium hydroxide by mass and calcined in a muffle furnace at a calcination temperature of 900 ℃ for 1.5h. After calcination, the charge contains about 5% sodium chromate, which is added to cold water and filtered in a drum filter. Chromate in the filtrate can be recovered. After washing the filter cake, it is dried at 300 ℃ and then crushed to obtain chromium oxide finished product. If borax or boric acid containing% boron trioxide is added instead of 5% sodium hydroxide and the calcination time is extended to 2h, the chromium oxide hue has a blue phase. |
| category | toxic substances |
| flammability hazard characteristics | non-combustible; toxic chromium-containing fumes are produced at the fire site; |
| storage and transportation characteristics | warehouse low temperature, ventilation, drying |
| fire extinguishing agent | water, carbon dioxide, dry powder, sand |
| occupational standard | TWA 0.5 mg (chromium)/m3 |
| toxic substance data | information provided by: pubchem.ncbi.nlm.nih.gov (external link) |
Last Update：2024-04-09 02:00:06
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Raw Materials for trioxochromium