Chromium trioxide

Chromium trioxide
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IUPAC name	Chromium(VI) oxide
Other names	Chromium trioxide
Identifiers
CAS number	1333-82-0
RTECS number	GB6650000
SMILES	O=Cr(=O)(O)
Properties
Molecular formula	CrO3
Molar mass	99.994 g/mol
Appearance	Dark red solid
Density	2.70 g/cm3, solid
Melting point	197 °C
Boiling point	250 °C, decomposes
Solubility in water	63 g/100 mL
Hazards
EU classification	Oxidizer (O), very toxic (T+), dangerous for the environment (N)
NFPA 704	0 3 1 OX
S-phrases	S53 S45 S60 S61
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

The acid anhydride of chromic acid is chromium trioxide or chromium(VI) oxide; industrially, this compound is sometimes sold as "chromic acid". This compound is an intensely-colored dark red/orange brown, water-soluble, granular solid which is stable by itself, but is a strong oxidant which will react when mixed with many things that can be oxidized. Ethanol, for example, will ignite on contact with it.

Production

Chromium trioxide is produced commercially by the reaction of sodium dichromate with concentrated sulfuric acid.

Structure and chemistry

Chromium trioxide consists of chains of tetrahedrally coordinated chromium atoms that share vertices. Each chromium atom therefore has "half share of two oxygen atoms" and two oxygen atoms that are not shared, giving an overall stoichiometry of 1:3.
Chromium trioxide decomposes above 197°C liberating oxygen eventually giving Cr₂O₃. The reaction of chromium trioxide with organic substances is potentially explosive. In spite of this, CrO₃ is used in organic chemistry as an oxidant, often dissolved in acetic acid, or acetone in the case of the Jones oxidation.

Safety

Chromium trioxide is highly toxic, corrosive, and carcinogenic.

References

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