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.
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
02 · GHS classification
Hazards and label elements
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
| 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. |
Precautionary statements: P201, P260, P261, P270, P271, P272, P273, P280, P301, P302, P304, P308, P310, P313, P314, P330, P331, P333, P352, P391, P501
03 · 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.
| 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 | |
| Melting point | 197 °C (386.6 °F) | HSDB | |
| 196.11 °C (385 °F) | CAMEO | ||
| Density | 2.7 g/cm³ | HSDB | |
| 2.7 g/cm³ | CrO3 | NIOSH | |
| 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 | |
| Vapor pressure | Very low | HSDB | |
| Very low (NIOSH, 2024) | CAMEO | ||
| Autoignition temperature | May ignite organic materials on contact. (USCG, 1999) | CAMEO | |
| 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.
04 · Handling and storage
Storing and handling 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)
Incompatible materials
Incompatible materials: Organic materials, Phosphorus, powdered metals.
Source: Hazardous Substances Data Bank (HSDB)
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 →
Next