Nitrogen Tri-Iodide (NI3) is a (usually) pale bownish glop composed primarily of ammonia and iodine. Extremely unstable. Saying 'it would explode if you looked at it wrong' is not an exaggeration. Applied as a liquid to any surface, it will dry and crystalise, and wait for anything to touch it. It is semi-stable when wet, and when dry is unstable to the point that even the force of a paper airplane landing on it will make it go off.

Do not make it. If you make it, do not use it. If you make it, please, in the name of the ever-loving Jehovah, do not store it -- it loses stability over time, so the longer you keep it, the more prone you are to having your nose blown off your face. I am, as such, not including a recipe for it here. Someone has to think about the children, don't they?

By the way, Heinlein's process, from SF book "Farnham's Freehold", doesn't work, either -- you can't use iodine liquid for this. You must use iodine crystals.

This used to be Nitrogen trioxide but do to much, uh, resistance, it has been changed. Don't bitch about the name again, 'cause this one is straight from the University of Chicago.

One use for wet triiodide that was told to me by my high school chemistry teacher was to paint those little knobs on the bottom of the toilet seat with it, and gently lay them back down.

When the unsuspecting user sits on the seat, Bang!!, and they are surrounded by a cloud of purple smoke. Enough to scare the crap outa you.

Nitrogen triiodide (NI3) is an unstable, explosive compound, which constitutes of one nitrogen atom bound to three iodine atoms. It is a covalent compound of nitrogen analogous to ammonia (NH3). Pure NI3 decomposes at 0 C, so it cannot exist in standard conditions, but it can exist if coordinated as an ammine complex. (NI3 . (1,3,5)NH3) is a red-black crystalline solid. It is stable in aqueous solution, but when dry, it detonates literally because of a touch of a feather.

There are a lot on unstable explosives, but nitrogen triiodide has everything against its stability. First, NI3 is a nitrogen explosive. The N-N bond in elemental nitrogen (N2) has a large bond enthalpy: -945 kJ mol-1. That is, when nitrogen molecules are created, a lot of energy is released. Analogous compounds, like ammonia (Hf = -43 kJ mol-1), need energy for decomposition. Not so with nitrogen triiodide: its decomposition actually releases energy. (Hf = +192 kJ mol-1.)

Not only thermodynamics make the molecule unstable. The molecule is barely holding together. The iodine atoms are larger than the nitrogen atom, so the oppositely-charged(1 iodines are forced close together. It's easy to tear them off from the nitrogen.

If you look at the reaction and still ask why would it be explosive, look at the phases: a solid decomposes completely into gases. This causes a rapid and large increase of volume. When this is combined with just-look-at-it-wrong activation energy and the infernal release of energy, there'll be a sonic boom, which goes through the crystal and detonates the NI3 into elements.

Decomposition is violent, produces a loud report and releases elemental nitrogen and toxic gaseous iodine, which leaves permanent stains and can damage lungs.

2NI3(s) -> N2(g) + 3I2(g)

This reaction is used frequently as a demonstration with everything carefully prepared and safe. There's better application: synthesize some NI3, VERY carefully place one crystal (1-2 mm) on a piece of tape, lay another piece on it to protect the crystal and leave these "anti-personnel mines" in places where they will be stepped on. Someone will discover how nitrogen triiodide decomposes... It'd be plain stupid to use any larger amounts than one crystal for this prank.

Pure NI3 is difficult to make and the way to synthesize it was discovered as late as in 1990. The conditions are unusual: at -30 C, boron nitride and iodine monofluoride react in an chloroform (CH3Cl) solution to produce boron fluoride and nitrogen triiodide. As mentioned before, pure NI3 decomposes at 0 C.

BN + 3IF -> NI3 + BF3

Impure NI3 (ammine complex) is easy to synthesize from iodine and excessive aqueous ammonia. The iodine and the ammonia must be pure enough to achieve this. Iodine can be purified by evaporating it off from the impure mixture and then condensing. The products are an triiodide-ammonia complex and hydroiodic acid. It is impossible to remove the ammonia from the resulting complex.

2NH3 + 3I2 -> NI3 . NH3 + 3HI
4NH3 + 3I2 -> NI3 . 3NH3 + 3HI
6NH3 + 3I2 -> NI3 . 5NH3 + 3HI

1) Partial charges due to electronegativity, not full electron charge units.

Sources: Cotton, Simon. Nitrogen Tri-iodide. URL:
chem, sci. sci.chem FAQ.

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