· The chromium atoms are in oxidation state +6 in both, and the chromate and dichromate ions are fairly strong oxidizing agents. Chromium in the +6 (or VI) oxidation state is often referred to as hexavalent chromium.
· In an aqueous solution, chromate and dichromate anions are in a chemical equilibrium.
+ 2 H3
+ 3 H2
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)