Osmium tetroxide
An osmium coordination entity consisting of four oxygen atoms bound to a central osmium atom via covalent double bonds. — ChEBI
Safety documents & references
2 indexed referencesFind a product-specific SDS
Safety guides and government classification records are not a manufacturer’s SDS. Match supplier, product number, concentration, physical form, region and revision before using a document.
Identity & molecular properties
Source-linked values| CAS number | 20816-12-0 | ChEBI ↗ |
| Molecular formula | O4Os | ChEBI ↗ |
| Molar mass | 254.226 g/mol | ChEBI ↗ |
| Monoisotopic mass | 255.94114 Da | ChEBI ↗ |
| Formal charge | 0 | ChEBI ↗ |
| ChEBI identifier | CHEBI:88215 | ChEBI ↗ |
Cross-source molecular data
PubChem| Molar mass | 254.2 g/mol | PubChem ↗ |
| Exact mass | 255.94114 Da | PubChem ↗ |
PubChem computed values are shown separately from the ChEBI record. An exact InChIKey match was used to connect the records. Molecular descriptors do not describe a supplied product’s purity, particle size or performance.
Names & structural identifiers
Copy any identifierosmium tetroxidetetraoxoosmiumVUVGYHUDAICLFK-UHFFFAOYSA-N[O]=[Os](=[O])(=[O])=[O]InChI=1S/4O.OsNames & synonyms
Names are supplied by ChEBI. Trade names and related synonyms may describe a broader product context.
Classification & relationships
ChEBI ontologyRoles recorded in ChEBI
Database role annotations describe reported biological or chemical roles; they are not product approvals or recommendations for use.
Safety classification · Japan
NITE / Japanese governmentosmium tetraoxide · 780
| Endpoint | Reported classification |
|---|---|
| Acute toxicity （Oral） | Category 3 |
| Acute toxicity （Inhalation: Vapours） | Category 1 |
| Skin corrosion/irritation | Category 1A-1C |
| Serious eye damage/eye irritation | Category 1 |
| Specific target organ toxicity - Single exposure | Category 1 (respiratory system, liver, kidney, adrenal gland, spleen) |
| Specific target organ toxicity - Repeated exposure | Category 1 (respiratory system), Category 2 (kidney, liver, adrenal gland, spleen, hematopoietic system) |
Selected source-reported endpoints. Other endpoints, rationales and conditions remain in the original classification. Missing or unlisted information does not mean non-hazardous. This is not a global classification or transport decision.
Read the original NITE classificationMass ↔ amount of substance
Calculated from sourced massUses 254.226 g/mol from ChEBI. Assumes the substance described by this record; no purity or concentration correction is applied.
Elemental composition
Theoretical mass fractionsOsOCalculated theoretical mass fractions from the reported formula and PubChem periodic-table atomic masses. These are not assay or purity results.
Research & patent references
Selected source associationsSources & record history
Checked 27 Sep 2026Release 255, 9 September 2026. ChEBI three-star (manually annotated) source entry. View original record ↗ · CC BY 4.0
PubCAS formats source data, connects references and computes explicitly labelled conversions. CAS cross-references are supplied by ChEBI; they do not constitute CAS verification or endorsement.