Substance profile
Osmium Tetroxide
Osmium Tetroxide is pale yellow solid; monoclinic crystals with an acrid, chlorine-like odor.
01 · Identification
What Osmium Tetroxide is
Osmium Tetroxide is pale yellow solid; monoclinic crystals with an acrid, chlorine-like odor. Its molecular formula is O4Os and its molecular weight is 254.2 g/mol. It boils at 130 °C, melts at 40.6 °C.
Under the GHS it carries the signal word Danger.
Other names for Osmium Tetroxide
- osmium tetraoxide
- osmic acid
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 |
|---|---|
| H310 | Fatal in contact with skin. |
| H330 | Fatal if inhaled. |
| H300 | Fatal if swallowed. |
| H314 | Causes severe skin burns and eye damage. |
Precautionary statements: P260, P270, P271, P280, P301, P302, P304, P310, P330, P331, P352
03 · Physical and chemical properties
Osmium Tetroxide 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 | 130 °C (266 °F) | NIOSH | |
| 130 °C (266 °F) | at 760 mmHg | CAMEO | |
| Melting point | 40.6 °C (105.1 °F) | HSDB | |
| 40.56 °C (105 °F) | NIOSH | ||
| Density | 5.1 g/cm³ | Calculated | HSDB |
| 5.1 g/cm³ | NIOSH | ||
| Solubility | Sol in benzene, alcohol, ether, ammonium hydroxide, and phosphorus oxychloride; solubility in carbon tetrachloride @ 25 deg: 375 g/100 g | HSDB | |
| In water, 7.24 (g/100 g) at 25 °C | at 25 °C | HSDB | |
| (77 °F): 6% | at 25 °C | NIOSH | |
| Vapor pressure | 7 mmHg | NIOSH | |
| 11 mmHg | at 27 °C | HSDB | |
| Lower explosive limit (LEL) | Noncombustible Solid | NIOSH | |
| Vapor density | 8.8 (air = 1) | ICSC | |
| Odor threshold | Air odor threshhold: 0.0019 ppm v/v. Water odor threshhold: 0.012 ppm w/v (amount in water that generates the air odor threshhold in a closed system). | HSDB | |
| Odor Threshold Low: 0.0019 [mg/m3] | Haz-Map | ||
| Odor threshold from NJ "Hazardous Substance Fact Sheet" | Haz-Map | ||
| Critical temperature and pressure | 405 °C (761 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Handling and storage
Storing and handling Osmium Tetroxide
Storage conditions
Separated from combustible and reducing substances, food and feedstuffs. Ventilation along the floor.
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Contact with hydrochloric acid will cause formation of poisonous chlorine gas. Contact with easily oxidized organic materials may cause fires and explosions.
Source: Hazardous Substances Data Bank (HSDB)
Reactivity
OSMIUM TETROXIDE is incompatible with hydrochloric acid and easily oxidizes organic materials. Contact with other materials may cause fire. (NIOSH, 2024). Reacts explosively with 1-methylimidazole [J. Chem. Soc., Dalton Trans., 1979, 1084].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Osmium Tetroxide in the storage compatibility matrix →