O

Osmium tetroxide

IUPAC: tetraoxoosmium

O4Os Laboratory Reagents CAS 20816-12-0
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Quick Reference
Formula / NotationO4Os
CAS Number20816-12-0
Molecular Weight254.2
Melting Point105 °F (NIOSH, 2024)
Boiling Point266 °F at 760 mmHg (NIOSH, 2024)
Density5.1 (NIOSH, 2024) - Denser than water; will sink
Solubility6 % at 77 °F (NIOSH, 2024)
AppearanceOsmium tetroxide appears as a colorless or yellow solid with a pungent odor of chlorine. Begins to sublime below melting point. Soluble in alcohol. Toxic by inhalation and a strong irritant to the ...
Also Known Astetraoxoosmium; 20816-12-0; Osmium tetraoxide; Osmic acid; Perosmic oxide; Osmium(VIII) oxide; Osmic acid anhydride; Osmium oxide (OsO4), (T-4)-; Perosmic acid anhydride; RCRA waste number P087
CategoryLaboratory Reagents

What is Osmium tetroxide?

Osmium tetroxide is an osmium coordination entity consisting of four oxygen atoms bound to a central osmium atom via covalent double bonds. It has a role as a NMR chemical shift reference compound, a fixative, an oxidising agent, a poison and a histological dye.

Formula & Notation

O4Os

IUPAC Name: tetraoxoosmium

Other Names / Synonyms: tetraoxoosmium; 20816-12-0; Osmium tetraoxide; Osmic acid; Perosmic oxide; Osmium(VIII) oxide; Osmic acid anhydride; Osmium oxide (OsO4), (T-4)-; Perosmic acid anhydride; RCRA waste number P087

Properties & Characteristics

Appearance: Osmium tetroxide appears as a colorless or yellow solid with a pungent odor of chlorine. Begins to sublime below melting point. Soluble in alcohol. Toxic by inhalation and a strong irritant to the .... Molecular formula: O4Os. Molecular weight: 254.2 g/mol. Boiling point: 266 °F at 760 mmHg (NIOSH, 2024). Melting point: 105 °F (NIOSH, 2024). Density: 5.1 (NIOSH, 2024) - Denser than water; will sink. Solubility: 6 % at 77 °F (NIOSH, 2024). Vapor pressure: 7 mmHg (NIOSH, 2024).

Physical Data

PropertyValue
Melting Point105 °F (NIOSH, 2024)
Boiling Point266 °F at 760 mmHg (NIOSH, 2024)
Density5.1 (NIOSH, 2024) - Denser than water; will sink
Molecular Weight254.2
Solubility6 % at 77 °F (NIOSH, 2024)
AppearanceOsmium tetroxide appears as a colorless or yellow solid with a pungent odor of chlorine. Begins to sublime below melting point. Soluble in alcohol. Toxic by inhalation and a strong irritant to the ...

Uses & Applications

Used as a synthetic reagent for transformations including oxidation, reduction, coupling, or functional group manipulation.

Safety Information

Hazardous reagent. May be toxic, corrosive, flammable, or reactive. Use in fume hood with full PPE. Consult SDS before use.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Osmium tetroxide
Formula O4Os
CAS Number 20816-12-0
Molecular Weight 254.2
Synonyms tetraoxoosmium; 20816-12-0; Osmium tetraoxide; Osmic acid; Perosmic oxide; Osmium(VIII) oxide; Osmic acid anhydride; Osmium oxide (OsO4), (T-4)-; Perosmic acid anhydride; RCRA waste number P087

Frequently Asked Questions

Osmium tetroxide is an osmium coordination entity consisting of four oxygen atoms bound to a central osmium atom via covalent double bonds. It has a role as a NMR chemical shift reference compound, a fixative, an oxidising agent, a poison and a histological dye.

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Editorial standards: Chemical data is sourced from peer-reviewed literature, CAS Registry, NIST WebBook, and PubChem. Safety information reflects guidance from OSHA, ECHA, and IAEA. For educational purposes only — always consult official SDS documentation and qualified professionals before handling chemicals.