Substance profile
Chromium trioxide
Chromium trioxide is dark red, bipyramidal prismatic crystals, flakes or granular powder and is odorless.
01 · Identification
What Chromium trioxide is
Chromium trioxide is dark red, bipyramidal prismatic crystals, flakes or granular powder and is odorless. Its molecular formula is CrO3 and its molecular weight is 99.994 g/mol. It boils at 250 °C, melts at 197 °C.
Under the GHS it carries the signal word Danger. It is classed as carcinogens.
02 · Identifiers
Chromium trioxide identifiers and molecular data
Chromium trioxide CAS number and EC number
Chromium trioxide molecular formula and molecular weight
Other names for Chromium trioxide
- chromic acid
- hexavalent chromium
- CrO3
- Chromia (Cro3)
- Chromic Acid (Cro3): Chromic Anhydride
- Chromic Anhydride
- Chromic Oxide
- Chromic Trioxide
- Chromium (6+) Trioxide
- Chromium Oxide
- Chromium Oxide (Cr4O12)
- Chromium Trioxide, Anhydrous
- Chromium Vi Oxide
- Chromium(Vi) Oxide
- Chromium(Vi) Oxide (1:3)
- chromium (VI) trioxide
03 · GHS classification
Chromium trioxide hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Chromium trioxide pictograms and signal word
Chromium trioxide hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Oxidising liquids or Oxidising solids | Category 1 | H271 | GHS03 |
| Acute toxicity - oral GHS chapter 3.1 | Category 3 | H301 | GHS06 |
| Acute toxicity - dermal GHS chapter 3.1 | Category 3 | H311 | GHS06 |
| Acute toxicity - inhalation GHS chapter 3.1 | Category 1 or 2 | H330 | GHS06 |
| Skin corrosion/irritation GHS chapter 3.2 | Category 1A or 1B or 1C | H314 | GHS05 |
| Respiratory sensitisation GHS chapter 3.4 | Category 1 or 1A or 1B | H334 | GHS08 |
| Skin sensitisation GHS chapter 3.4 | Category 1 or 1A or 1B | H317 | GHS07 |
| Germ cell mutagenicity GHS chapter 3.5 | Category 1A or 1B | H340 | GHS08 |
| Carcinogenicity GHS chapter 3.6 | Category 1A or 1B | H350 | GHS08 |
| Specific target organ toxicity - repeated exposure GHS chapter 3.9 | Category 1 | H372 | GHS08 |
| Hazardous to the aquatic environment - acute GHS chapter 4.1 | Category 1 | H400 | GHS09 |
| Hazardous to the aquatic environment - chronic GHS chapter 4.1 | Category 1 | H410 | GHS09 |
Where two values are shown with “or”, the hazard statement is shared by more than one category or by more than one class, and the code alone does not say which. H272, for example, belongs to oxidising liquids and to oxidising solids — the physical state decides. The binding answer for a specific entry is in the CLP Annex VI table itself.
Chromium trioxide hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H271 | May cause fire or explosion; strong oxidiser. |
| H350 | May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H340 | May cause genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H361f | Suspected of damaging fertility. |
| H330 | Fatal if inhaled. |
| H311 | Toxic in contact with skin. |
| H301 | Toxic if swallowed. |
| H372 | Causes damage to organs <or state all organs affected, if known> through prolonged or repeated exposure <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H314 | Causes severe skin burns and eye damage. |
| H334 | May cause allergy or asthma symptoms or breathing difficulties if inhaled. |
| H317 | May cause an allergic skin reaction. |
| H400 | Very toxic to aquatic life. |
| H410 | Very toxic to aquatic life with long lasting effects. |
This page lists only the codes assigned to Chromium trioxide. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Chromium trioxide
Our own Chromium trioxide safety data sheet walks through all sixteen sections of the published data. What it is not is the document an inspector asks for: an SDS is issued for a product by its supplier, so the sheet covering the grade actually standing in your store exists only in that supplier’s version. Collecting those and keeping them current as suppliers revise them is a separate job.
04 · Precautionary statements
Chromium trioxide precautionary statements
CLP Annex VI assigns 21 precautionary statements to Chromium trioxide. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Disposal
What has to happen to the contents and the empty container.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Chromium trioxide name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | хромен(VI) триоксид |
| Spanish español | Trióxido de cromo(VI) |
| Czech čeština | oxid chromový |
| Danish dansk | chromtrioxid |
| German Deutsch | Chrom(VI)trioxid Chromsäureanhydrid |
| Estonian eesti | kroom(VI)trioksiid |
| Greek ελληνικά | τριοξείδιο του χρωμίου(VI) |
| English English | chromium (VI) trioxide |
| French français | trioxyde de chrome (VI) |
| Croatian hrvatski | kromov(VI) trioksid |
| Italian italiano | triossido di cromo |
| Latvian latviešu | hroma (VI) trioksīds |
| Lithuanian lietuvių | chromo (VI) trioksidas |
| Hungarian magyar | króm(VI)-trioxid |
| Maltese Malti | triossidu tal-kromu (VI) |
| Dutch Nederlands | chroom(VI)oxide |
| Polish polski | tlenek chromu(VI) tritlenek chromubezwodnik chromowy |
| Portuguese português | trióxido de crómio(VI) |
| Romanian română | trioxid de crom (VI) |
| Slovak slovenčina | oxid chrómový |
| Slovenian slovenščina | kromov(VI) trioksid |
| Finnish suomi | kromi(VI)trioksidi |
| Swedish svenska | krom(VI)trioxid |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Chromium trioxide GHS label elements
Everything CLP Annex VI fixes for Chromium trioxide, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Chromium trioxide
- May cause fire or explosion; strong oxidiser.
- May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- May cause genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Suspected of damaging fertility.
- Fatal if inhaled.
- Toxic in contact with skin.
- Toxic if swallowed.
- Causes damage to organs <or state all organs affected, if known> through prolonged or repeated exposure <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Causes severe skin burns and eye damage.
- May cause allergy or asthma symptoms or breathing difficulties if inhaled.
- May cause an allergic skin reaction.
- Very toxic to aquatic life.
- Very toxic to aquatic life with long lasting effects.
- Obtain special instructions before use.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Avoid breathing dust/fume/gas/mist/vapours/spray.
- Do not eat, drink or smoke when using this product.
- Use only outdoors or in a well-ventilated area.
- Contaminated work clothing should not be allowed out of the workplace.
- Avoid release to the environment.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF ON SKIN:
- IF INHALED:
- IF exposed or concerned:
- Immediately call a POISON CENTER/doctor/…
- Get medical advice/attention.
- Get medical advice/attention if you feel unwell.
- Rinse mouth.
- Do NOT induce vomiting.
- If skin irritation or rash occurs:
- Wash with plenty of water/…
- Collect spillage.
- Dispose of contents/container to …
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Chromium trioxide in the GHS label constructor →
07 · Health hazards
Chromium trioxide health hazards and exposure limits
Chromium trioxide hazard summary
CrVI compounds are irritants, sensitizers, and may be corrosive to the skin. CrVI compounds are respiratory tract irritants and may cause pulmonary sensitization. CrVI may cause acute tubular necrosis and liver injury. [ATSDR Case Studies] Highly corrosive to skin; [Quick CPC] Chromium trioxide (chromic acid) is a water-soluble hexavalent chromium compounds. A corrosive substance that can cause injury to the skin, eyes, and respiratory tract; May cause skin sensitization, kidney injury, and asthma after prolonged contact; [ICSC] See Chromium and linked occupational diseases.
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
Chromium trioxide carcinogenicity classification
Evaluation: There is sufficient evidence in humans for the carcinogenicity of chromium(VI) compounds. Chromium(VI) compounds cause cancer of the lung. Also positive associations have been observed between exposure to Chromium(IV) compounds and cancer of the nose and nasal sinuses. There is sufficient evidence in experimental animals for the carcinogenicity of chromium(VI) compounds. Chromium(VI) compounds are carcinogenic to humans (Group 1). /Chromium(VI) compounds/
Source: Hazardous Substances Data Bank (HSDB)
Chromium Hexavalent Compounds: known to be human carcinogens. /Chromium hexavalent compound/
Source: Hazardous Substances Data Bank (HSDB)
An IARC group and a CLP classification answer different questions. IARC judges whether the evidence for cancer in humans is strong enough; CLP Annex VI is the legally binding EU classification. A substance can carry one and not the other.
Chromium trioxide occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 0.005 [mg/m3], as Cr(VI) | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | (as CrO3): TWA 0.005 mg/m3 See Appendix C | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | (as Cr): Ca TWA 0.0002 mg/m3 (8-hours) See Appendix ASee Appendix C | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 15 mg Cr(VI)/m3 ; A potential occupational carcinogen. (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 250 mg/cu m (as Cr(II)). /Chromium(II) compounds (as Cr)/ | Hazardous Substances Data Bank (HSDB) |
| IDLH | 25 mg/cu m (as Cr(III)). /Chromium(III) compounds (as Cr)/ | Hazardous Substances Data Bank (HSDB) |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
Chromium trioxide properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Chromium trioxide boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 250 °C (482 °F) | approximate | HSDB |
| 250 °C (482 °F) | decomposes | NIOSH | |
| 250 °C (482 °F) | decomposes, at 760 mmHg | CAMEO |
Chromium trioxide melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 197 °C (386.6 °F) | HSDB | |
| 196.11 °C (385 °F) | CAMEO |
Chromium trioxide density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 2.7 g/cm³ | HSDB | |
| 2.7 g/cm³ | CrO3 | NIOSH |
Chromium trioxide solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | In water, 1667 g/L (EU Method A.6 (Water Solubility)) | HSDB | |
| In water, 167.299 lb/100 lb water at 70 °F | at 21.11 °C | HSDB | |
| In water, 169 g/100 g water at 25 °C | at 25 °C | HSDB |
Chromium trioxide vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | Very low | HSDB | |
| Very low (NIOSH, 2024) | CAMEO |
Chromium trioxide autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | May ignite organic materials on contact. (USCG, 1999) | CAMEO |
Chromium trioxide lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | CrO3: Noncombustible Solid, but will accelerate the burning of combustible materials. | NIOSH |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Chromium trioxide fire and explosion behaviour
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Chromium trioxide fire potential
Powerful oxidizer ... contact with combustible material may cause fire.
Source: Hazardous Substances Data Bank (HSDB)
10 · Handling and storage
Chromium trioxide storage and handling
Chromium trioxide reactive group
CAMEO Chemicals places Chromium trioxide in the reactive groups Anhydrides, Oxidizing Agents, Strong. Compatibility with other chemicals is worked out from the group, not from the individual substance — which is why two substances you have never seen react can still be flagged as a pair that must be separated.
A reactive group is a CAMEO Chemicals (US NOAA) grouping, not a GHS hazard class: it has no code, no category and no legal force. It is what the storage compatibility matrix on this site computes from.
Chromium trioxide safe storage
Provision to contain effluent from fire extinguishing. Separated from combustible substances, reducing agents, bases and food and feedstuffs. Well closed. Store in an area without drain or sewer access.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Chromium trioxide storage conditions
Keep container tightly closed in a dry and well-ventilated place. Hygroscopic. Heat sensitive. Storage class (TRGS 510): Strongly oxidizing hazardous materials
Source: Hazardous Substances Data Bank (HSDB)
Chromium trioxide incompatible materials
Incompatible materials: Organic materials, Phosphorus, powdered metals.
Source: Hazardous Substances Data Bank (HSDB)
Chromium trioxide reactivity
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].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Chromium trioxide in the storage compatibility matrix →
11 · Transport
Chromium trioxide UN number and transport classification
Transport classification is a separate system from the GHS classification above. It decides how a package is marked and how a load may be carried; it does not follow from the workplace label, and the workplace label does not follow from it. The entries below are linked by CAS number, never by name.
Chromium trioxide under UN 1463 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| CHROMIUM TRIOXIDE, ANHYDROUS | 5.1 | OTC | II | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 5.1 is “Oxidizing substances” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Chromium trioxide, anhydrous | 5.1 | II | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 5.1 is “Oxidizer” (49 CFR 173.2).
12 · Questions
Chromium trioxide — frequently asked questions
What is the CAS number of Chromium trioxide?
The CAS number of Chromium trioxide is 1333-82-0. Its EC number is 215-607-8.
What is the chemical formula of Chromium trioxide?
The molecular formula of Chromium trioxide is CrO3 and its molecular weight is 99.994 g/mol.
What does a Chromium trioxide label have to show?
Under CLP Annex VI the label for Chromium trioxide carries the pictograms Flame over circle, Skull and crossbones, Health hazard, Corrosion and Environment and the signal word is Danger.
Is Chromium trioxide flammable?
CLP Annex VI assigns Chromium trioxide no flammability hazard class. That is not a statement that it cannot burn: the harmonised list only records the hazards that were assessed for it.
Is Chromium trioxide a carcinogen?
Yes. CLP Annex VI classifies Chromium trioxide as a category 1A or 1B carcinogen and assigns it H350: may cause cancer.
What is the exposure limit for Chromium trioxide?
The US occupational exposure limit reported for Chromium trioxide is 0.005 [mg/m3], as Cr(VI) (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of Chromium trioxide?
The boiling point reported for Chromium trioxide is 250 °C (482 °F), approximate (HSDB).
What is the melting point of Chromium trioxide?
The melting point reported for Chromium trioxide is 197 °C (386.6 °F) (HSDB).
How should Chromium trioxide be stored?
Keep container tightly closed in a dry and well-ventilated place. Hygroscopic. Heat sensitive. Storage class (TRGS 510): Strongly oxidizing hazardous materials (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Chromium trioxide
Keep going: substances starting with C, or search the whole database by name, CAS number, pictogram or signal word.
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