Chromium(VI) oxide peroxide
| IUPAC name
Chromium(VI) oxide peroxide
| Other names
Chromium oxide peroxide
|Molar mass||131.99 g/mol|
|Appearance||Deep blue (solution only)|
|Soluble, but rapidly decomposes|
|Solubility|| Soluble in diethyl ether, ethyl acetate, amyl alcohol and its esters, valeric ether|
Insoluble in benzene, carbon disulfide, toluene
|Safety data sheet||None|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Chromium(VI) oxide peroxide, also known as chromium(VI) peroxide or chromium 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
Chromium peroxide will form a complex with pyridine and bipyridine, which is one of the few ways of stabilizing the compound.
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.
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+
The dissolution of chromium trioxide in crushed ice, 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.
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.
Chromium(V) oxide peroxide cannot be stored, as it 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.
- Journal of the American Chemical Society; vol. 17; (1895); p. 41 - 43
- Wiede, O. F.; Ber.; vol. 31; (1898); p. 516 - 524
- Byers, H. G.; Reid, E. E.; American Chemical Journal; vol. 32; (1904); p. 503 - 513