Ammonium dichromate

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Template:Chembox E numberTemplate:Chembox SolubilityInWater
Ammonium dichromate
IUPAC name Ammonium dichromate
Other names Ammonium Pyrochromate
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RTECS number HX7650000
Molar mass 252.07 g/mol
Appearance Orange crystals
Density 2.15 g/cm3
Melting point
Boiling point
see dichromate
Main hazards oxidizer
S-phrases S53 S45 S60 S61
Related compounds
Other cations {{{value}}}
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

Ammonium dichromate is the inorganic compound with the formula (NH4)2Cr2O7. This salt is sometimes known as Vesuvian Fire, because of its use in the formation of tabletop "volcanoes". It has been used in pyrotechnics and in the early days of photography.

The volcano demonstration involves igniting a pile of the salt, which initiates the following conversion:

(NH4)2Cr2O7(s) → Cr2O3(s) + N2(g) + 4H2O(g)

Like the well-known explosive ammonium nitrate, ammonium dichromate contains both an oxidizer (dichromate) and a reducer (ammonium).[1] The reaction proceeds to completion once initiated. This demonstration finds only limited use because the chromium(III) oxide ash produced by this reaction is toxic, possibly carcinogenic.


  1. G.A.P. Dalgaard, A.C. Hazell and R.G. Hazell "The Crystal Structure of Ammonium Dichromate, (NH4)2Cr2O7" Acta Chemica Scandinavica A28 (1974) 541-545

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