Sciencemadness Discussion Board

Hello everyone! (Also Nitrogen Triiodide)

Dead Eye Dave - 2-8-2019 at 00:46

Hi folks!!

I discovered this forum while trying to find some information about Nitrogen triiodide.
Everybody seems to be very knowledgeable and friendly which is better than you find in some corners of the internet!
I do not really use many internet forums so if this is too long for a first post I do apologise.

I have not played with much chemistry since my days at school, (many decades ago) but have recently had my interest rekindled.
I have no intention of trying to make any Nitrytrytyiodidey, but I would like to ask questions about making it. I know that does make it look like I want to make it, but really I don't.
So, if there's anyone that wouldn't mind answering my questions that would be brilliant.
Q1: I have been told that there is more than one way to make NI3. What is / are the most common methods?
Q2: If you were in a hurry to make your NI3 what method would be best to use?
Q3: How much NI3 would you need to make for a small demo in a small room to half a dozen people vs how much would you make to do an open air demo, to a crowd of people who are at the opposite end of a large field, but you want even the people at the back to be impressed and even a little bit scared by the demo?
Thanks in advance for any answers and information!!

Best regards

Dave

Sulaiman - 2-8-2019 at 01:26

Welcome,
In UK the legal limit for nitrogen triiodide is 500mg - for demonstration and educational purposes only.
In other places it may be illegal, check your local laws/regulations.

500mg gives quite a bang.

I used to 'play' with NI3 a lot in my youth,
larger quantities are genuinely dangerous and can detonate violently when dry,
a feather or a fly can initiate detonation.

experiment many times to practice before demonstrating,
too wet and it is very disappointing,
too dry and it is INCREDIBLY sensitive.

Make the NI3 only where and when needed - for safety.

https://www.youtube.com/results?search_query=Nitrogen+triiod...

P.S. I suggest that you use plasticware rather than glassware,
and you should use goggles and some type of ear defenders.

[Edited on 2-8-2019 by Sulaiman]

AJKOER - 5-8-2019 at 07:35

What I do remember among group of friends experimenting with NI3.xNH3 (where x can go as high as 8 when prepared in cold conditions, and more NH3 gas means more power!), there were unexpected explosions and skin patches of iodine (explosion product apparently includes hot iodine vapor).

So yes, goggles a must and a face mask recommended as well.

Link to a prior thread: https://www.sciencemadness.org/whisper/viewthread.php?tid=45... .
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I would expect the path to NI3 mirrors that of NCl3 and may proceed as follows citing Wikipedia (https://en.wikipedia.org/wiki/Chloramine ):

“Gaseous chloramine can be obtained from the reaction of gaseous ammonia with chlorine gas (diluted with nitrogen gas):
2 NH3(g) + Cl2(g) ⇌ NH2Cl(g) + NH4Cl(s)”

And:

“In an acidic medium at pH values of around 4, chloramine disproportionates to form dichloramine, which in turn disproportionates again at pH values below 3 to form nitrogen trichloride:
2 NH2Cl + H+ ⇌ NHCl2 + NH4+
3 NHCl2 + H+ ⇌ 2 NCl3 + NH4+ “

where in the current case, we would replace Cl2 with I2. Relatedly, one possibly could view the creation of NI3 as arising the successive action of HOI (from aqueous iodine, which also correspondingly produces HI, lowering pH) acting on aqueous ammonia with iodine in excess:

3 x [ I2 + H2O = HI + HOI ]

NH3 + HOI = NH2I + H2O

NH2I + HOI = NHI2 + H2O

NHI2 + HOI = NI3 + H2O

Net: 3 I2 + NH3 (aq) = 3 HI + NI3

although pure NI3 has not been formed with ammonia, only adducts, NI3.xNH3 where x = 1 to 8 (see https://www.fourmilab.ch/documents/chemistry/NI3/ ).

Based on Atomistry.com on NI3 (see http://nitrogen.atomistry.com/nitrogen_iodide.html ), which is an extract from an old chemistry journal, a different take, to quote:

"The reaction between iodine and ammonia appears to proceed in three stages. Firstly, hypoiodous acid and ammonium iodide are produced:

NH4OH + I2 = HOI + NH4I;

and the hypoiodous acid further combines with ammonia to form ammonium hypoiodite:

NH4OH + HOI = NH4IO + H2O.

Finally, the ammonium hypoiodite decomposes into nitrogen iodide:

3NH4IO ⇔ N2H3I3 + NH4OH + 2H2O.

The last reaction is apparently reversible, as the nitrogen iodide redissolves in strong ammonia."
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A cited preparation path by Marvin from yet another SM thread (http://www.sciencemadness.org/talk/viewthread.php?tid=3905 ) to quote:

"As for making NI3.NH3, I prefer the process of dissolving iodine in a solution of potassium iodide and adding that to ammonia. Saving the filtrate gets the potassium iodide back as well as the half of the iodine that doesnt go into making NI3."
----------------------------------------------------

Based on the proposed elemental iodine, water and ammonia chemistry, I think an interesting path, for small amounts of NI3, would arise from the action of sunlight on an iodide in acidic H2O2:

I- + hv --> •I + e-

•I + I- = •I2- (the atomic iodine is rapidly complexed by iodide)

which in the presence of H+ from dissociation of H2O2:

H2O2 = H+ + HO2-

H+ + e- = •H

And further with H2O2:

•H + HO2- --> •OH + OH- (this is, in effect, the one electron reduction of H2O2)

•OH + H2O2 = •HO2 + H2O

where the •HO2 radical is reported to release complexed iodine to elemental iodine (based on this related work with Br2, see 'Hydroperoxyl radical (HO2•) oxidizes dibromide radical anion (•Br2−) to bromine (Br2) in aqueous solution: Implications for the formation of Br2 in the marine boundary layer', see the work by Brendan M. Matthew, et al, fully available (for free) at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... ):

•I2- + •HO2 = I2 + HO2- (+ H+ --> H2O2 regenerated)

where the free iodine is then treated with ammonia yielding NI3.xNH3 per suggested path above. Only small amounts of H2O2 are recommended in this prep (see comments below).

I am wondering whether anyone agrees on the possible incidental creation here of some NH4IO3 also, upon evaporation in the presence of ammonia, as a result of any disproportionation of HOI occurring prior to the introduction of ammonia:

5 HOI --> HIO3 + 2I2 + 2H2O

In fact, the action of increasing higher concentrations of H2O2 on I2 is a path to iodate (https://pubs.rsc.org/en/content/articlelanding/2001/cp/b1065...), which could increase NH4IO3 formation.

Another hypothetical variation of the above path would be to omit the H2O2 and pass O2/air into the aqueous iodide at pH < 4.8 in strong sunlight (the riched in UV from the presence of large bodies of water or ice, the better). Then, treat with ammonia.

Note: My suggested paths avoids elemental iodine as times have changed.

[Edited on 6-8-2019 by AJKOER]

[Edited on 6-8-2019 by AJKOER]

AJKOER - 7-8-2019 at 08:56

Link to related comments in the Energetic Materials at https://www.sciencemadness.org/whisper/viewthread.php?tid=45... which also cites a link to a good detailed prep by GreenD.

Also, note comments suggesting maintaining a presence of concentrated ammonia to reduce the risk of detonation on handling/storage.
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My personal opinion, on what is occurring, is that an excess of NH3 creates a safe compound, distinct from NI3.NH3, based on the cited Wikipedia equilibrium reaction above:

2 NH2Cl + H+ ⇌ NHCl2 + NH4+
3 NHCl2 + H+ ⇌ 2 NCl3 + NH4+

Or, in the proposed case for iodine in the last reaction above:

2 NHI2.NH3 + NHI2 + H+ ⇌ 2 NI3.NH3 + NH4+

where an excess of ammonia would move the above equilibrium reaction to the left, due in part, by possibly:

NHI2 + NH3 = NHI2.NH3

And more likely by:

NH3 + H2O = NH4+ + OH-

OH- + H+ = H2O

So, in essence, I am suggesting that the dissolving of NI3.NH3 in concentrated ammonia does produce a different compound that is not explosive, in accord with the chlorine chemistry for NH2Cl vs. NCl3 (see https://en.wikipedia.org/wiki/Chloramine ), but not precisely aqueous NH4IO, as was suggested many years ago (1917) by Mellor.

Support for my position, I cite this old text at https://books.google.com/books?id=1iQ7AQAAMAAJ&pg=PA539&... to quote relating to the compound N2H3I3:

"Many have demonstrated that the compound contains hydrogen; and, in consequence, the formula has been variously given as N2H3I3, NH2I, NHI2, etc."

where N2H3I3 corresponds to NI3.NH3. The presence of NH2I and NHI2 would be expected in the equilibrium reactions per my prior Wiki citation based on chloramine.

[Edited on 8-8-2019 by AJKOER]

chornedsnorkack - 9-8-2019 at 09:40

Actually, you need iodine monofluoride to produce NI3.

And iodine monofluoride is itself a tricky thing to produce. (It does not explode, but it dismutes).

nezza - 13-8-2019 at 11:46

I can attest to the sensitivity of Nitrogen Tri-iodide. I made a small batch at home when I was an "A" level chemistry student. I put it on a small dish on filter paper to dry overnight. The next morning I checked if it was dry by poking it with a stick. It was. It blew the dish to smithereens and I am lucky (I wear glasses) that all I got in my eye was a bit of iodine which stung like hell. Since then I've been very wary about making any.

Lion850 - 5-11-2019 at 14:21

For a small test in the back garden it is probably too easy to make.
- Buy strong household ammonia from your local department store.
- Get some iodine crystals, maybe on eBay.
- Grind a little bit - quarter of a small teaspoon - of iodine crystals into powder.
- Put in a small plastic cup and fill 3/4 with the household ammonia.
- stir for some 10 minutes, never face the cup opening towards you.
- Scoop out a tiny amounts of the black residue and put on solid surfaces (bricks, wood) in the sun
- Wait until fully (I suppose that depends on the weather in your area) and tap the black spots with a long stick...like a broom handle...should get a sharp bang with small purple cloud.
I made it quite often when a kid 40 years ago and again recently once to show my kids. In my experience my 'crude' NI3 never went off when wet, only once dried in the sun. Sometimes however the sun's heat would set it off before I got around to tapping it.

wg48temp9 - 6-11-2019 at 02:13

Quote: Originally posted by Lion850  
For a small test in the back garden it is probably too easy to make.
- Buy strong household ammonia from your local department store.
- Get some iodine crystals, maybe on eBay.
- Grind a little bit - quarter of a small teaspoon - of iodine crystals into powder.
- Put in a small plastic cup and fill 3/4 with the household ammonia.
- stir for some 10 minutes, never face the cup opening towards you.
- Scoop out a tiny amounts of the black residue and put on solid surfaces (bricks, wood) in the sun
- Wait until fully (I suppose that depends on the weather in your area) and tap the black spots with a long stick...like a broom handle...should get a sharp bang with small purple cloud.
I made it quite often when a kid 40 years ago and again recently once to show my kids. In my experience my 'crude' NI3 never went off when wet, only once dried in the sun. Sometimes however the sun's heat would set it off before I got around to tapping it.


Dry NI3 can be set of by photographic flash gun 12in away. Even wet NI3 will puff off iodine vapour when subject to a flash. I don't know if its the IR/UV or visible light from the flash that is responsible. So bright sunlight may well do it too assuming a curious insect does not investigate it first.

PS: See if a laser pointer can set it off.

[Edited on 11/6/2019 by wg48temp9]