What is ammonium dichromate?

Ammonium dichromate is an excellent compound with the chemical formula NH4 (2Cr2O7). This material with a molar mass of 252.07 g/mol and a density of 2.115 g/cm3 is soluble in alcohol and acetone. The appearance of ammonium dichromate is orange to red crystals and due to the presence of chromium with an oxidation number of +6, it has turned it into a very toxic substance with corrosive and carcinogenic properties. The existence of ammonium ions (NH ₄ ⁺ ) and dichromate (Cr ₂ O ₇ ^{2 –} ) has made this material an ionic solid. The ionicity of ammonium dichromate and the existence of dipolar dipolar force and ion-dipolar attraction and hydrogen bond make it soluble in water.

Decomposition of ammonium dichromate

Ammonium dichromate is decomposed into chromium (III) oxide and gaseous nitrogen as a result of heating according to the following formula.

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

The nitrogen gas produced in this reaction is very toxic and dangerous, that’s why all safety precautions must be observed when using ammonium dichromate.

Application of ammonium dichromate

• Used in laboratories as a source of pure nitrogen in lithography
• Used as a colorant in dyeing seeds
• Used in the leather industry for tanning
• Used in the experiment of the sixth science volcano mountain
• Used in fireworks
• Used in radiography

The volcano test

The volcano experiment is one of the most interesting experiments in the 6th grade science book. In order to perform this test, we need some ammonium dichromate, a porcelain crucible, a heat source, and most importantly laboratory safety equipment such as laboratory glasses, gloves, and laboratory coats.

To perform the test, it is sufficient to pour some orange ammonium dichromate powder into the porcelain pot, then bring the existing heat source close to it. Ammonium dicerate begins to decompose from the top inwards. Chromium(III) oxide is obtained as a result of decomposition of the green powder. This powder is soluble in water, and after dissolving, a yellow to orange solution is obtained.