Chromium(VI) oxide peroxide

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Chromium(VI) oxide peroxide
IUPAC name
Chromium(VI) oxide peroxide
Other names
Chromium(VI) pentoxide
Chromium(VI) peroxide
Chromium oxide peroxide
Chromium pentoxide
Jmol-3D images Image
Molar mass 131.99 g/mol
Appearance Deep blue (solution only)
Boiling point Decomposes
Soluble, but rapidly decomposes
Solubility Soluble in diethyl ether, ethyl acetate, amyl alcohol and its esters, valeric ether
Insoluble in benzene, carbon disulfide, toluene
Related compounds
Related compounds
Chromium trioxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Chromium(VI) oxide peroxide, also known as chromium(VI) peroxide or chromium(VI) pentoxide (CrO5) is an unstable compound formed by the addition of an acidified hydrogen peroxide solution to solutions of metal chromates, such as sodium or potassium chromate, and followed by extraction from aqueous solution with an organic solvent, such as diethyl ether.



Chromium(VI) peroxide is not very stable in water, and will rapidly decompose to Cr(III) ions, releasing oxygen.

2 CrO5 + 7 H2O2 + 6 H+ → 2 Cr3+ + 10 H2O + 7 O2

It can be stabilized by the addition of an solvent immiscible with water, such as diethyl ether, ethyl acetate, during the addition of the hydrogen peroxide.

Chromium peroxide will form a complex with pyridine.


Chromium(VI) oxide peroxide is a very unstable deep blue compound. It is soluble in water, but rapidly breaks down, and soluble as well as stable in solvents such as diethyl ether, ethyl acetate, amyl alcohol and its esters (formiate, acetate, butyrate, valerate), amyl chloride, valeric ether. It is insoluble in many other solvents, such as aniline, benzene, bergamot oil, CCl4, CS2, castor oil, kerosene, ligroin, nitrobenzene, paraffins, terpene alcohols, toluene, wintergreen oil.[1]


Chromium peroxide is not sold by any entity due to its instability and has to be made in situ.


The addition of an acidified solution of 3% hydrogen peroxide to sodium chromate will cause it to turn from yellow to dark blue-brown. The chromate salt reacts with hydrogen peroxide and an acid to give chromium peroxide, water, and the metal salt of the acid.

Na2CrO4 + 2 H2O2 + 2 H+ → CrO5 + 3 H2O + 2 Na+

Diethyl ether or ethyl acetate is added to stabilize the product.[2]

The dissolution of chromium trioxide on ice is followed by the addition of cooled diethyl ether and finally cooled hydrogen peroxide (at 0 °C) is added. The solution is shaken and the water layer frozen on an ice bath.[3]

Potassium peroxochromate can also be used instead of potassium chromate.[4]




Chromium(V) oxide peroxide is a strong oxidizer, but it's generally too unstable to pose any serious risk. However, if produced in high quantity, it may spontaneously explode.


Cannot be stored, rapidly decomposes.


Since it quickly breaks down to Cr(III) in water, it can be simply poured down the drain. Though it's best to decompose it first, for safety reasons.


  1. Journal of the American Chemical Society; vol. 17; (1895); p. 41 - 43
  3. Wiede, O. F.; Ber.; vol. 31; (1898); p. 516 - 524
  4. Byers, H. G.; Reid, E. E.; American Chemical Journal; vol. 32; (1904); p. 503 - 513

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