General Description
A dark purplish red solid. Density 2.67 g/cm3. Melting point 385°F (196°C). Under prolonged exposure to fire or heat the containers may explode. Highly toxic. A confirmed human carcinogen.
Reactivity Profile
CHROMIUM TRIOXIDE is a powerful oxidizing agent. Can react violently upon contact with reducing reagents, including organic matter, leading to ignition or explosion. Dangerously reactive with acetone, alcohols, alkali metals (sodium, potassium), ammonia, arsenic, dimethylformamide, hydrogen sulfide, phosphorus, peroxyformic acid, pyridine, selenium, sulfur, and many other chemicals [Sax, 9th ed., 1996, p. 852]. Noncombustible but can accelerate the burning of combustible materials. Sufficient heat may be generated from the reaction with combustible materials to ignite the mass. Aqueous solutions corrode many metals rapidly. Often mixed with sulfuric acid to make "cleaning solution" for glass. Used cleaning solution in closed bottles may explode due to the build up of gaseous carbon dioxide arising from oxidation of organic impurities [Bryson, W. R., Chem. Brit., 1975, 11, p. 377].
Air & Water Reactions
Deliquescent. Water soluble, giving acidic solutions.
Health Hazard
Toxic by ingestion. Inhalation of dust is toxic. Fire may produce irritating, corrosive and/or toxic gases. Contact with substance may cause severe burns to skin and eyes. Runoff from fire control or dilution water may cause pollution.
Potential Exposure
Chromium trioxide is used in plating and metal treatment, as a corrosion inhibitor; and as an oxidant; in aluminum anodizing, dye; ink, and paint manufacturing, tanning, engraving; and photography.
Fire Hazard
These substances will accelerate burning when involved in a fire. May explode from heat or contamination. Some may burn rapidly. Some will react explosively with hydrocarbons (fuels). May ignite combustibles (wood, paper, oil, clothing, etc.). Containers may explode when heated. Runoff may create fire or explosion hazard.
First aid
Move victim to fresh air. Call 911 or emergency medical service. Give artificial respiration if victim is not breathing. Do not use mouth-to-mouth method if victim ingested or inhaled the substance; give artificial respiration with the aid of a pocket mask equipped with a one-way valve or other proper respiratory medical device. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with substance, immediately flush skin or eyes with running water for at least 20 minutes. For minor skin contact, avoid spreading material on unaffected skin. Keep victim warm and quiet. Effects of exposure (inhalation, ingestion, or skin contact) to substance may be delayed. Ensure that medical personnel are aware of the material(s) involved and take precautions to protect themselves. Medical observation is recommended for 24 to 48 hours after breathing overexposure, as pulmonary edema may be delayed. As first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a drug or other inhalation therapy.
Shipping
UN1463 (anhydrous), Chromium trioxide, anhydrous, Chromium trioxide, anhydrous, Hazard Class: 5.1; Labels: 5.1-Oxidizer, 6.1-Poisonous materials, 8-Corrosive material. UN1755 (solution), Hazard class: 8; Labels: 8-Corrosive material.
Incompatibilities
Chromium trioxide is a strong oxidizer. The solution in water is a strong acid. Reacts violently with bases and is corrosive. Contact with reducing agents; fuels, organic chemicals, flammable and combustible materials, causing fire and explosion hazard. This chemical decomposes above 250C to chromic oxide and oxygen with increased fire hazard. Attacks metals in the presence of moisture.
Description
Chromium hydroxide (Cr2O(OH)4) is a bright bluish-green pigment prepared by the calcinations of bichromate with boric acid at 500°C. The mass during cooling is hydrolyzed with water, which yields the hydrate.
Waste Disposal
Reduce to Cr(III). If material cannot be recovered and recycled, dispose of sludge in a chemical waste landfill.
Definition
ChEBI: A chromium oxide composed of a single chromium bound (oxidation state +6) to three oxygens; the acidic anhydride of chromic acid.
Definition
chromium trioxide: A redcompound, CrO3; rhombic; r.d. 2.70;m.p. 196°C. It can be made by carefuladdition of concentrated sulphuricacid to an ice-cooled concentratedaqueous solution of sodium dichromatewith stirring. The mixture isthen filtered through sintered glass,washed with nitric acid, then dried at120°C in a desiccator.
Chromium(VI) oxide is an extremelypowerful oxidizing agent,especially to organic matter; it immediatelyinflames ethanol. It is anacidic oxide and dissolves in water toform ‘chromic acid’, a powerful oxidizingagent and cleansing fluid forglassware. At 400°C, chromium(VI)oxide loses oxygen to givechromium(III) oxide.
Flammability and Explosibility
Chromium(VI) oxide is not combustible but is a strong oxidizing agent and can accelerate the burning rate of combustible materials. Contact with easily oxidized organic or other combustible materials (including paper and oil) may result in ignition, violent combustion, or explosion. The use of dry chemical, carbon dioxide, Halon, or water spray extinguishers is recommended for fires involving chromium (VI) compounds.
storage
Chromium trioxide should be handled in a fume hood to avoid the inhalation of dust, and impermeable gloves should be worn at all times to prevent skin contact. The practice of using chromate solutions to clean glassware should be avoided. Chromium trioxide should be stored in areas separated from readily oxidized materials.
Properties and Applications
TEST ITEM
|
STANDARD
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Appearance
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Dark red flake
|
DENSITY
|
2.7
|
Melt Point
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197°C
|
Chromic anhydride(CrO3)
|
99.6 % min
|
Sulfate (SO4)
|
0.10% max
|
Water insolubles
|
0.03% max
|
Sodium (Na)
|
-
|
Turbidity
|
15% max
|
Purification Methods
It separates when potassium or sodium dichromate are dissolved in conc H2SO4. Dry it in a vacuum desiccator over NaOH pellets. It is a hygroscopic, powerful oxidant and can ignite with organic compounds. It is a skin and pulmonary IRRITANT. [Keyes et al. Industrial Chemicals (Lowenheim & Moran eds.) 4th edn J. Wiley pp 270-274 1975.] CANCER SUSPECT.