Chrom

Gefahreninformationscode (GHS)

• Bildanzeige (GHS)

  

• Alarmwort

  Warnung

• Gefahrenhinweise

  H228：Entzündbarer Feststoff.

  H351：Kann vermutlich Krebs verursachen.

  H410：Sehr giftig für Wasserorganismen mit langfristiger Wirkung.

• Sicherheit

  P201：Vor Gebrauch besondere Anweisungen einholen.

  P202：Vor Gebrauch alle Sicherheitshinweise lesen und verstehen.

  P210：Von Hitze, heißen Oberflächen, Funken, offenen Flammen und anderen Zündquellenarten fernhalten. Nicht rauchen.

  P240：Behälter und zu befüllende Anlage erden.

  P280：Schutzhandschuhe/Schutzkleidung/Augenschutz tragen.

  P308+P313：BEI Exposition oder falls betroffen: Ärztlichen Rat einholen/ärztliche Hilfe hinzuziehen.

  P405：Unter Verschluss aufbewahren.

Chromium Chemische Eigenschaften,Einsatz,Produktion Methoden

• ERSCHEINUNGSBILD

  GRAUES PULVER.

• PHYSIKALISCHE GEFAHREN

  Staubexplosion der pulverisierten oder granulierten Substanz in Gemischen mit Luft möglich.

• CHEMISCHE GEFAHREN

  Chrom ist eine katalytisch wirksame Substanz und kann Reaktionen in Gang setzen bei Kontakt mit vielen organischen und anorganischen Substanzen. Feuer- und Explosionsgefahr.

• ARBEITSPLATZGRENZWERTE

  TLV:(als Cr-Metall, Cr(III)-Verbindungen) 0.5 mg/m?(als TWA); Krebskategorie A4 (nicht klassifizierbar als krebserzeugend für den Menschen); (ACGIH 2005).
  MAK nicht festgelegt (DFG 2005).
  

• INHALATIONSGEFAHREN

  Eine gesundheitsschädliche Partikelkonzentration in der Luft kann beim Dispergieren schnell erreicht werden.

• WIRKUNGEN BEI KURZZEITEXPOSITION

  WIRKUNGEN BEI KURZZEITEXPOSITION:
  Reizt möglicherweise Augen und Atemwege mechanisch.

• LECKAGE

  Verschüttetes Material in Behältern sammeln; falls erforderlich durch Anfeuchten Staubentwicklung verhindern. Persönliche Schutzausrüstung: Atemschutzgerät, P2-Filter für schädliche Partikel.

• R-Sätze Betriebsanweisung:

  R11:Leichtentzündlich.
  R20/21/22:Gesundheitsschädlich beim Einatmen,Verschlucken und Berührung mit der Haut.
  R34:Verursacht Verätzungen.
  R40:Verdacht auf krebserzeugende Wirkung.
  R23:Giftig beim Einatmen.

• S-Sätze Betriebsanweisung:

  S16:Von Zündquellen fernhalten - Nicht rauchen.
  S26:Bei Berührung mit den Augen sofort gründlich mit Wasser abspülen und Arzt konsultieren.
  S36/37/39:Bei der Arbeit geeignete Schutzkleidung,Schutzhandschuhe und Schutzbrille/Gesichtsschutz tragen.
  S45:Bei Unfall oder Unwohlsein sofort Arzt zuziehen (wenn möglich, dieses Etikett vorzeigen).
  S36/37:Bei der Arbeit geeignete Schutzhandschuhe und Schutzkleidung tragen.
  S27:Beschmutzte, getränkte Kleidung sofort ausziehen.

• Beschreibung

  Chromium as a metallic element was first discovered over 200 years ago, in 1797. But the history of chromium really began several decades before this. In 1761, in the Beresof Mines of the Ural Mountains, Johann Gottlob Lehmann obtained samples of an orange-red mineral, which he called ‘Siberian red lead.’ He analyzed this mineral in 1766 and discovered that it contained lead “mineralized with a selenitic spar and iron particles.” The mineral he found was crocoite, a lead chromate (PbCrO4).

• Chemische Eigenschaften

  Chromium may exist in one of three valence states in compounds, , , and . The most stable oxidation state is trivalent chromium; Hexavalent chromium is a less stable state. Chromium (element) blue-white to steel-gray, lustrous, brittle, hard, odorless solid. Elemental:

• Physikalische Eigenschaften

  Chromium is a silvery white/gray, hard, brittle noncorrosive metal that has chemical andphysical properties similar to the two preceding elements in period 4 (V and Ti). As one of thetransition elements, its uses its M shell rather than its outer N shell for valence electrons whencombining with other elements. Its melting point is 1,857°C, its boiling point is 2,672°C,and its density is 7.19 g/cm³.

• Isotopes

  There are 26 isotopes of the element chromium; four are stable and foundin nature, and the rest are artificially produced with half-lives from a few microsecondsto a few days. The four stable isotopes and their percentage of contribution to thetotal amount of chromium on Earth are as follows: ⁵⁰Cr = 4.345%, ⁵²Cr = 83.789%,⁵³Cr = 9.501%, and ⁵⁴Cr = 2.365%. Cr-50 is radioactive but has such a long halflife—1.8×10⁺¹⁷ years—that it is considered to contribute about 4% to the total amount ofchromium found on Earth.

• Origin of Name

  From the Greek word chroma or chromos, meaning “color,” because of the many colors of its minerals and compounds.

• Occurrence

  Chromium is the 21st most common element found in the Earth’s crust, and chromiumoxide (Cr₂O₃) is the 10th most abundant of the oxide compounds found on Earth. It is notfound in a free metallic state.The first source of chromium was found in the mineral crocoite. Today it is obtained fromthe mineral chromite (FeCr₂O₄), which is found in Cuba, Zimbabwe, South Africa, Turkey,Russia, and the Philippines. Chromite is an ordinary blackish substance that was ignored formany years. There are different grades and forms of chromium ores and compounds, based onthe classification of use of the element. Most oxides of chromium are found mixed with othermetals, such as iron, magnesium, or aluminum.Astronauts found that the moon’s basalt rocks contain several times more chromium thanis found in basalt rocks of Earth.

• Charakteristisch

  Chromium is a hard, brittle metal that, with difficulty, can be forged, rolled, and drawn,unless it is in a very pure form, in which case the chromium is easier to work with. It is anexcellent alloying metal with iron. Its bright, silvery property makes it an appropriate metal toprovide a reflective, non-corrosive attractive finish for electroplating.Various compounds of chromium exhibit vivid colors, such as red, chrome green, andchromate yellow, all used as pigments.

• History

  Chromium was discovered in 1797 by Vauquelin, who prepared the metal the next year, chromium is a steel-gray, lustrous, hard metal that takes a high polish. The principal ore is chromite (FeCr2O4), which is found in Zimbabwe, Russia, South Africa, Turkey, Iran, Albania, Finland, Democratic Republic of Madagascar, the Philippines, and elsewhere. The U.S. has no appreciable chromite ore reserves. Chromium is usually produced by reducing the oxide with aluminum. Chromium is used to harden steel, to manufacture stainless steel, and to form many useful alloys. Much is used in plating to produce a hard, beautiful surface and to prevent corrosion. Chromium is used to give glass an emerald green color. It finds wide use as a catalyst. All compounds of chromium are colored; the most important are the chromates of sodium and potassium (K2CrO4) and the dichromates (K2Cr2O7) and the potassium and ammonium chrome alums, as KCr(SO4)2·12H2O. The dichromates are used as oxidizing agents in quantitative analysis, also in tanning leather. Other compounds are of industrial value; lead chromate is chrome yellow, a valued pigment. Chromium compounds are used in the textile industry as mordants, and by the aircraft and other industries for anodizing aluminum. The refractory industry has found chromite useful for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stability of crystalline structure. Chromium is an essential trace element for human health. Many chromium compounds, however, are acutely or chronically toxic, and some are carcinogenic. They should be handled with proper safeguards. Natural chromium contains four isotopes. Twenty other isotopes are known. Chromium metal (99.95%) costs about $1000/kg. Commercial grade chromium (99%) costs about $75/kg.

• Verwenden

  The best-known use of chromium is for the plating of metal and plastic parts to producea shiny, reflective finish on automobile trim, household appliances, and other items where abright finish is considered attractive. It also protects iron and steel from corrosion.It is used to make alloys, especially stainless steel for cookware, and items for whichstrength and protection from rusting and high heat are important.Its compounds are used for high-temperature electrical equipment, for tanning leather, asa mordant (fixes the dyes in textiles so that they will not run), and as an antichalking agentfor paints.Some research has shown that, even though most chromium compounds are toxic, a smalltrace of chromium is important for a healthy diet for humans. A deficiency produces diabeteslike symptoms, which can be treated with a diet of whole-grain cereal, liver, and brewer’s yeast.Chromium’s most important radioisotope is chromium-51, which has a half-life of about27 days. It is used as a radioisotope tracer to check the rate of blood flowing in constrictedarteries.Some chromium compounds (e.g., chromium chloride, chromic hydroxide, chromic phosphate) are used as catalysts for organic chemical reactions.In 1960 the first ruby laser was made from a ruby crystal of aluminum oxide (Al₂O₃). Thesecrystals contain only a small amount of chromium, which stores the energy and is responsiblefor the laser action. A small amount of chromium found in the mineral corundum is responsible for the bright red color of the ruby gemstone.

• Verwenden

  Chromium is used in the manufacture ofits alloys, such as chrome-steel or chromenickel-steel. It is also used for chromeplatingof other metals, for tanning leather,and in catalysts. It occurs in chromite ores(FeO·Cr2O3).

• Verwenden

  In manufacture of chrome-steel or chrome-nickel-steel alloys (stainless steel), nonferrous alloys, heat resistant bricks for refractory furnaces. To greatly increase strength, hardness and resistance of metals to abrasion, corrosion and oxidation. For chrome plating of other metals; leather tanning; as pigment and mordant; wood preservative. Use of 51Cr as diagnostic aid see sodium chromate(VI).

• Vorbereitung Methode

  Chromium metal is prepared by reducing the ore in a blast furnace with carbon (coke) or silicon to form an alloy of chromium and iron called ferrochrome, which is used as the starting material for the many iron-containing alloys that employ chromium. Chromium to be used in iron-free alloys is obtained by reduction or electrolysis of chromium compounds.Chromiumisdif?culttoworkinthepuremetalform; it is brittle at low temperatures, and its high melting point makes it dif?cult to cast.

• Definition

  chromium: Symbol Cr. A hard silverytransition element; a.n. 24;r.a.m. 52.00; r.d. 7.19; m.p. 1857°C;b.p. 2672°C. The main ore ischromite (FeCr₂O₄). The metal has abody-centred-cubic structure. It is extractedby heating chromite withsodium chromate, from whichchromium can be obtained by electrolysis.Alternatively, chromite can be heated with carbon in an electricfurnace to give ferrochrome, whichis used in making alloy steels. Themetal is also used as a shiny decorativeelectroplated coating and in themanufacture of certain chromiumcompounds.
  At normal temperatures the metalis corrosion-resistant. It reacts withdilute hydrochloric and sulphuricacids to give chromium(II) salts.These readily oxidize to the more stablechromium(III) salts. Chromiumalso forms compounds with the +6oxidation state, as in chromates,which contain the CrO4^2- ion. The elementwas discovered in 1797 byVauquelin.

• Allgemeine Beschreibung

  Very hard gray solid with a metallic luster.

• Air & Water Reaktionen

  May be pyrophoric, as dust. Insoluble in water.

• Reaktivität anzeigen

  Chromium reacts violently with NH4NO3, N2O2, Li, NO, KClO3, SO2 . Metal dusts when suspended in atmospheres of carbon dioxide may ignite and explode.

• Hazard

  Hexavalent chromium compounds are questionable carcinogens and corrosive on tissue, resulting in ulcers and dermatitis on prolonged contact.

• Hazard

  Even though chromium may be a necessary trace element in our diets, many of its compounds are very toxic when ingested. Some are very explosive when shocked or heated (e.g., chromium nitrate) or when in contact with organic chemicals. Dust from the mining of chromium ores, which is found in igneous rocks, is carcinogenic and can cause lung cancer, even when small amounts are inhaled. Workers in industries that produce and use chromium are subject to bronchogenic cancer if precautions are not taken.

• Health Hazard

  The toxicity of chromium alloys and compoundsvaries significantly. Chromium metaldoes not exhibit toxicity. Divalent and trivalentcompounds of chromium have a loworder of toxicity. Exposure to the dusts ofchromite or ferrochrome alloys may causelung diseases, including pneumoconiosis andpulmonary fibrosis.
  Among all chromium compounds onlythe hexavalent salts are a prime health hazard.Cr⁶⁺ is more readily taken up bycells, than any other valence state of themetal. Occupational exposure to these compoundscan produce skin ulceration, dermatitis,perforation of the nasal septa, and kidneydamage. It can induce hypersensitivityreactions of the skin and renal tubular necrosis.Examples of hexavalent salts are thechromates and dichromates of sodium, potassium,and other metals. The water-solublehexavalent chromium salts are absorbed intothe bloodstream through inhalation. Manychromium(VI) compounds are carcinogenic,causing lung cancers in animals and humans.The carcinogenicity may be attributed tointracellular conversion of Cr⁶⁺ to Cr³⁺,which is biologically more active. The trivalentCr³⁺ ion can bind with nucleic acid andthus initiate carcinogenesis.
  Paustenbach et al. (1996) reported a casestudy on the uptake and elimination ofCr(VI) in drinking water on a male volunteerwho ingested 2 L/day of water containing2 mg/L Cr(VI) for 17 consecutivedays. The total chromium was measured inurine, plasma and red blood cells. The eliminationhalf-life in plasma was 36 hoursand the bioavailability was estimated as 2%.The steady-state chromium concentrations inurine and blood were achieved after sevendays of Cr(VI) ingestion. This study furthermorerevealed that Cr(VI) in drinkingwater at concentrations below 10 mg/L couldbe completely reduced to Cr(III) prior tosystemic distribution. In a follow-up study,Kergen et al. (1997) examined the magnitudeof absorption, distribution and excretionof Cr(VI) in drinking water in human volunteersfollowing oral exposures to singleand repeated doses at 5 and 10 mg Cr(VI)/L.The data obtained from this study indicatedthat virtually all (> 99.7%) of the ingestedCr(VI) was reduced to Cr(III) before enteringthe blood stream. No toxicity was observed.The endogenous reducing agents within theupper GI tract and the blood were attributedto reduce hexavalent chromium into its trivalentstate and, thus, prevented any systemicuptake of Cr(VI). Such reduction appearedto be effective even under the fasting conditions.
  Wise et al. (2002) investigated the cytotoxicityand clastogenicity of both water-insolubleand water-soluble Cr(VI) compounds in primaryhuman bronchial fibroblasts and foundthat they were overall cytotoxic and genotoxicto human lung cells. Although the genotoxicmechanisms of both may be mediated bysoluble Cr(VI) ions the water-insoluble saltsapparently are the potent carcinogens comparedto the water-soluble salts (Wise et al.2004). Exposure to Cr(VI) enhanced the bindingof polycyclic aromatic hydrocarbons toDNA in human lung cells (Feng et al. 2003).Hexavalent chromium has been found to besynergistic to benzo a pyrene diol epoxide onmutagenesis and cell transformation.
  The catalytic effect of iron on enhancingthe rate of reduction of Cr(VI) byhuman microsomes has been reported earlier(Myers and Myers 1998). Various formsof exogenous iron markedly enhanced bothliver and lung microsomal rates of Cr(VI)reduction. Small increases in intracellulariron have shown to cause large increases inin the rate and extent of Cr(VI) reduction.Thus, individuals exposed simultaneously toCr(VI) and agents that may increase intracellulariron could, therefore, be at potentiallygreater risk for toxicity and carcinogenicityof Cr(VI).

• Brandgefahr

  Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.

• Industrielle Verwendung

  An elementary metal, chromium (symbol Cr)is used in stainless steels, heat-resistant alloys,high-strength alloy steels, electrical-resistancealloys, wear-resistant and decorative electroplating,and, in its compounds, for pigments,chemicals, and refractories. The specific gravityis 6.92, melting point 1510°C, and boiling point2200°C. The color is silvery white with a bluishtinge. It is an extremely hard metal; the electrodepositedplates have a hardness of 9 Mohs.It is resistant to oxidation, is inert to HNO3, butdissolves in HCl and slowly in H2SO4. At temperaturesabove 816°C, it is subject to intergranularcorrosion.
  Chromium occurs in nature only in combination.Its chief ore is chromite, from which itis obtained by reduction and electrolysis. It ismarketed for use principally in the form of masteralloys with iron or copper.Most pure chromium is used for alloyingpurposes such as the production of Ni–Cr orother nonferrous alloys where the use of thecheaper ferrochrome grades of metal is not possible.In metallurgical operations such as theproduction of low-alloy and stainless steels, thechromium is added in the form of ferrochrome,an electric-arc furnace product that is the formin which most chromium is consumed.
  Its bright color and resistance to corrosion makechromium highly desirable for plating plumbingfixtures, automobile radiators and bumpers,and other decorative pieces. Unfortunately,chrome plating is difficult and expensive. Itmust be done by electrolytic reduction ofdichromate in H2SO4 solution. It is customary,therefore, to first plate the object with copper,then with nickel, and finally, with chromium.

• mögliche Exposition

  Chromium metal is used in stainless and other alloy steels to impart resistance to corrosion, oxidation, and for greatly increasing the durability of metals; for chrome plating of other metals.

• Veterinary Drugs and Treatments

  Chromium supplementation may be useful in the adjunctive treatment of diabetes mellitus or obesity, particularly in cats; there is controversy whether this treatment is beneficial. It does not appear to be useful in dogs with diabetes mellitus.

• Erste Hilfe

  If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.
  Note to physician: In case of fume inhalation, treat for pulmonary edema. Give prednisone or other corticosteroidorally to reduce tissue response to fume. Positive-pressureventilation may be necessary. Treat metal fume fever withbed rest, analgesics, and antipyretics. The symptoms ofmetal fume fever may be delayed for 412 h followingexposure: it may last less than 36 h.

• Carcinogenicity

  Exposure to chromium compounds over a prolonged period has been observed in manyepidemiologicalstudiestoenhancetheriskofcancerof the respiratory organs among the exposed. The relationshipbetweenemploymentinindustriesproducingchromium compounds from chromite ore and enhanced risk of lungcancer iswell established.There isagreement inseveral studies that long-term exposure to some chromium-based pigments enhance the risk of lung cancer. An association has alsobeenobservedbetweenexposuretochromicacidinhard plating and lung cancer, but that association is not strong. Somestudieshaveweaklyindicatedexcessesofcancerofthe GItract,buttheresultsareinconsistentandarenotcon?rmed inwell-designedstudies.Thereisnoindicationthatchromite ore does have an associated enhanced risk of cancer. Although it has not yet been identi?ed which chromium compound (or compounds) is (are) responsible for enhanced risk of cancer in respiratory organs, there is general agreementthatitisthechromium(6+)speciesthatareresponsible for the elevated cancer risks and that the chromium species are not.

• Environmental Fate

  Chromium is distributed to the air, water, and soil from natural and anthropogenic sources. The environmental fate of chromium is dependent on the oxidation state and solubility of the compound and the environmental conditions affecting reduction or oxidation, such as pH. Oxidizing conditions favor the formation of Cr(VI) compounds, particularly at higher temperatures, while reducing conditions favor the formation of Cr(III) compounds. Chemical manufacturing and natural gas, oil, and gas combustion are the primary sources of chromium in the atmosphere.Most of the chromium in air eventually ends up in water or soil. Electroplating, textile manufacturing, cooling water, and leather tanning are major sources of chromium in wastewater discharges to surface waters.
  Chromium(III) is the predominant oxidation state of chromium in many soils. Cr(III) binds to soil and has low mobility. A lower soil pH favors the reduction of Cr(VI) to Cr(III). Runoff from soil and industrial processes may transport chromium to surface water.Cr(VI) compounds may leach into groundwater. The pH of the soil and aquatic environment is an important factor in chromium mobility, bioavailability, and toxicity. The chromate form predominates in most natural surface waters that are basic or neutral. The hydrochromate concentration increases in more acidic conditions.

• Lager

  Color Code—Green (metal, not powder): Generalstorage may be used. Prior to working with chromium youshould be trained on its proper handling and storage. A regulated, marked area should be established where this chemical is handled, used, or stored in compliance with OSHAStandard 1910.1045. Store in tightly closed containers in acool, well-ventilated area. Chromium must be stored toavoid contact with strong oxidizers (such as chlorine, bromine, and fluorine) since violent reactions occur. Sources ofignition, such as smoking and open flames, are prohibitedwhere chromium is used, handled, or stored in a mannerthat could create a potential fire or explosion hazard

• Versand/Shipping

  UN3089 Metal powders, flammable, n.o.s., Hazard Class: 4.1; Labels: 4.1-Flammable solid. UN1759 Corrosive solids, n.o.s., Hazard class: 8; Labels: 8-Corrosive material, Technical Name required

• Toxicity evaluation

  Chromium enters the air, water, and soil mostly in the chromium( III) and chromium(VI) forms. In air, chromium compounds are present mostly as fine dust particles, which eventually settle over land and water. Chromium can strongly attach to sediment and soil, and only a small amount is expected to dissolve in water and leach though the soil to groundwater. Fish do not accumulate much chromium in their bodies.
  Most chromium exposure in the general population is through ingestion of the chemical in food containing chromium( II), although exposure is also possible as a result of drinking contaminated well water, or living near uncontrolled hazardous waste sites containing chromium or industries that use chromium. Inhalation of chromium dust and skin contact during use in the workplace are the main routes of occupational exposure.

• Structure and conformation

  Two types of chromium crystals, α and β, are obtained depending on the growth method. The β type is semi-stable. It changes to a type above 800℃. The space lattice of β-Cr belongs to the hexagonal system, and its closely-packed hexagonal lattice has lattice constants of a=0.272 nm and c=0.442 nm. The space lattice of α-Cr belongs to the cubic system, and its body-centered cubic lattice has a lattice constant of a=0.28796 nm (18℃).
  

• Inkompatibilitäten

  Dust may be pyrophoric in air. Chromium metal (especially in finely divided or powder form) and insoluble salts reacts violently with strong oxidants, such as hydrogen peroxide, causing fire and explosion hazard. Reacts with diluted hydrochloric and sulfuric acids. Incompatible with alkalis and alkali carbonates

• Waste disposal

  Recovery and recycling is a viable alternative to disposal for chromium in plating wastes; tannery wastes; cooling tower blowdown water and chemical plant wastes.

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