Osmium tetroxide

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[2] °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)[3]
Structure[4]
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)	4
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)	3 0 1 OX
Lethal dose or concentration (LD, LC):
LCLo (lowest published)	1316 mg/m3 (rabbit, 30 min) 423 mg/m3 (rat, 4 hr) 423 mg/m3 (mouse, 4 hr)[5]
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 0.002 mg/m3[3]
REL (Recommended)	TWA 0.002 mg/m3 (0.0002 ppm) ST 0.006 mg/m3 (0.0006 ppm)[3]
IDLH (Immediate danger)	1 mg/m3[3]
Safety data sheet (SDS)	ICSC 0528
Related compounds
Other cations	Ruthenium tetroxide Hassium tetroxide
Related osmium oxides	Osmium(IV) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

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.^[6] This is most likely due to the presence of the impurity OsO₂, which is yellow-brown in colour.^[7] In biology, its property of binding to lipids has made it a widely-used stain in electron microscopy.