A powder that liberates a purple cloud on the caress of a feather?
That’s Nitrogen Triiodide (NI3), a contact explosive that releases nitrogen (N2) and a purple cloud of iodine gas (I2) at the slightest disturbance via the following reaction:
2 NI3 (s) → N2 (g) + 3 I2 (g) (ΔH=-290 kJ/mol)
As my friend Máximo and I love both explosive and colourful chemicals, we got straight to making this compound when we had time.
The preparation is very straightforward; you only need iodine and a standard cleaning product (ammonia) to make this exotic compound. However, I recommend that you not try it at home unless you’re really longing for a purple wallpaper (apart from the fact that it’s dangerous even in small amounts). First, elemental iodine (I2) is ground in a mortar and pestle to increase its surface area. Then, it is added to a dilute ammonia (NH3) solution. The following reaction takes place:
3I2(s) + NH3(aq) → NI3(s) + 3HI(aq)
Once the reaction had occurred, the mixture of ammonia and nitrogen triiodide was spread on filter paper and left to dry, as nitrogen triiodide is insensitive to contact when wet.
We took the wet filter paper outside and left it on a table to dry. A few minutes later, we got near the incipient explosive to detonate it and watch the beautiful purple cloud form.
What a deception… Despite hearing a small crack, the explosion was far less impressive than we had hoped for, likely due to the infinitesimal quantity we had produced for safety reasons.
You reap what you sow, and you detonate what you synthesise!
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