Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound with the formula OsO₄. The compound is noteworthy for its many uses, despite its toxicity and the rarity of osmium. It also has a number of unusual properties, one being that the solid is volatile. The compound is colourless, but most samples appear yellow.[5] This is most likely due to the presence of the impurity OsO₂, which is yellow-brown in colour.[6] In biology, its property of binding to lipids has made it a widely-used stain in electron microscopy.

Quick facts: Names, Identifiers, Properties, Structure[3],... ▼

Osmium tetroxide

Names

Preferred IUPAC name

Osmium tetraoxide

Systematic IUPAC name

Tetraoxoosmium

Other names

Osmium(VIII) oxide

Identifiers

CAS Number

20816-12-0^Y

3D model (JSmol)

Interactive image

ChEBI

CHEBI:88215^Y

ChemSpider

28158^Y

ECHA InfoCard

100.040.038

EC Number

244-058-7

MeSH

Osmium+tetroxide

PubChem CID

30318

RTECS number

RN1140000

UNII

P40W033BGM^Y

UN number

UN 2471

CompTox Dashboard (EPA)

DTXSID5042245

InChI

InChI=1S/4O.Os^Y
Key: VUVGYHUDAICLFK-UHFFFAOYSA-N^Y
InChI=1S/4O.Os
Key: VUVGYHUDAICLFK-UHFFFAOYSA-N
InChI=1/4O.Os/rO4Os/c1-5(2,3)4
Key: VUVGYHUDAICLFK-TYHKRQCIAE

SMILES

O=[Os](=O)(=O)=O

Properties

Chemical formula

OsO₄

Molar mass

254.23 g/mol

Appearance

White volatile solid

Odor

Acrid, chlorine-like

Density

4.9 g/cm³[1]

Melting point

40.25 °C (104.45 °F; 313.40 K)

Boiling point

129.7 °C (265.5 °F; 402.8 K)

Solubility in water

5.70 g/100 mL (10 °C)
6.23 g/100 mL (25 °C)

Solubility

Soluble in most organic solvents, ammonium hydroxide, phosphorus oxychloride

Solubility in CCl₄

375 g/100 mL

Vapor pressure

7 mmHg (20 °C)[2]

Structure[3]

Crystal structure

Monoclinic, mS20

Space group

C2/c

Lattice constant

a = 9.379 Å, b = 4.515 Å, c = 8.630 Å

α = 90°, β = 116.58°, γ = 90°

Lattice volume (V)

326.8 Å³

Formula units (Z)

Molecular shape

tetrahedral

Hazards

GHS labelling:

Pictograms

Signal word

Danger

Hazard statements

H300, H310, H314, H330

Precautionary statements

P260, P262, P264, P270, P271, P280, P284, P301+P310, P301+P330+P331, P302+P350, P303+P361+P353, P304+P340, P305+P351+P338, P310, P320, P321, P322, P330, P361, P363, P403+P233, P405, P501

NFPA 704 (fire diamond)