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Tom Mazanec
2012-Aug-09, 11:53 AM
This stuff is supposed to be so sensitive that an alpha particle will set it off. There are numerous videos on the web of gently touching it with a feather and BANG!
So why doesn't it immediately go off from the impact of air molecules banging into it? Wouldn't an air molecule hit the NI3 crystals harder than the molecules of feather?

Swift
2012-Aug-09, 12:40 PM
I actually made nitrogen triiodide, back in college, for a chemistry magic show. The plan was to make a small quantity, and while in solution, paint pieces of paper with it, then use the little pieces of paper. For example, you could take a 1 cm2 piece of paper with a thin coating, put it on a benchtop, hit it with a ruler, and get a pretty good bang.

It is pretty easy to handle when wet, but when dry it is very shock sensitive. Certainly light hits can set it off; I'm not shocked that a feather would work. But no an air molecule from random motion would not be more force than a feather. Consider this: to swing the feather you have to first move it through the air, so you are certainly applying more force than the air itself.

However, I've heard plenty of stories of small quantities of dry NI3 just "going off" spontaneously. It is basically considered unstable when dry, so it takes almost nothing to set it off. For all anyone knows, an alpha particle, a couple of air molecules, or a fly fart did set it off.

And kids - DO NOT TRY THIS AT HOME. This stuff is very dangerous and is so unstable when dry that professional demolition people do not use it.

trinitree88
2012-Aug-09, 02:12 PM
I actually made nitrogen triiodide, back in college, for a chemistry magic show. The plan was to make a small quantity, and while in solution, paint pieces of paper with it, then use the little pieces of paper. For example, you could take a 1 cm2 piece of paper with a thin coating, put it on a benchtop, hit it with a ruler, and get a pretty good bang.

It is pretty easy to handle when wet, but when dry it is very shock sensitive. Certainly light hits can set it off; I'm not shocked that a feather would work. But no an air molecule from random motion would not be more force than a feather. Consider this: to swing the feather you have to first move it through the air, so you are certainly applying more force than the air itself.

However, I've heard plenty of stories of small quantities of dry NI3 just "going off" spontaneously. It is basically considered unstable when dry, so it takes almost nothing to set it off. For all anyone knows, an alpha particle, a couple of air molecules, or a fly fart did set it off.

And kids - DO NOT TRY THIS AT HOME. This stuff is very dangerous and is so unstable when dry that professional demolition people do not use it.

Swift. Yep. As a rookie teacher, I was set off to making some upon the advice of a few considerably older and presumably wiser friends. Not so. I made ~ 25 grams....finding out years later people have been killed by ~10. While drying it out after lunch in a little miniature plaster volcano...I gave the class a test last period of the week. A student asked to sharpen his pencil, and when he began grinding away...~ 15 feet away, the vibrations from the sharpener set it off producing a large report, and a big purple cloud out of the volcano. Fortunately it wasn't well confined, so it sprinkled about. On Monday the custodian came up to me and asked why his broom kept exploding as he swept the floor of the class room. Never made it again. It will go off from speaking to it loudly from the sound waves. pete

Squink
2012-Aug-09, 02:16 PM
The stuff will go off by itself as it dries; not always, but often. Perhaps mini-zephyrs play a role in that, but gravity driven settling of piles of drying triiodide powder certainly provides enough of a jiggle to make a bang.

HenrikOlsen
2012-Aug-09, 02:18 PM
And kids - DO NOT TRY THIS AT HOME. This stuff is very dangerous and is so unstable when dry that professional demolition people do not use it.
But then, professional demolitions people do rather prefer their explosives to be such that you can beat them with a jackhammer for a fortnight without anything happening except some deformation.

Tom Mazanec
2012-Aug-09, 02:20 PM
It will go off from speaking to it loudly from the sound waves. pete
Good grief. This stuff is the "chooboom" from (I think) Rocky and Bullwinkle. It goes off if you sneeze near it!

swampyankee
2012-Aug-09, 02:24 PM
But then, professional demolitions people do rather prefer their explosives to be such that you can beat them with a jackhammer for a fortnight without anything happening except some deformation.

Can you blame them? They'd like to be able to go home without having to be vacuumed up.

HenrikOlsen
2012-Aug-09, 02:26 PM
I don't blame then, I think it's the sane choice.

Squink
2012-Aug-09, 02:33 PM
Can you blame them?The military at least gave it a try, back in '67 (https://docs.google.com/viewer?a=v&q=cache:WsLTFRLuvrwJ:www.dtic.mil/cgi-bin/GetTRDoc%3FAD%3DAD0387392+&hl=en&gl=us&pid=bl&srcid=ADGEESjVR4tMcZexw07cA5PJBjArWF0uOajYlCchKiSM ZOSvtkP9wn3b6Q6AjWbkIQsfcPoxLlsNpSP7YKQVjQ6X0hJ-1x_ssy1EXnWjyk6XpHDX6Exi_q5JeHR8N54CzpbE5thrGQDK&sig=AHIEtbStyp38stWpXzqNSfpTqWepg-bLPA) (see page 5)
After drying, the capsule was stepped on using the normal walking pressure of the foot...

Grey
2012-Aug-09, 03:20 PM
I'd always wanted to make some of this stuff when I was a kid (after reading about it in some science book). I was able to look up how to do it pretty easily, actually. But I never did, because all of the documentation I could find focused on how sensitive it was, but I couldn't find anywhere that it said how big of an explosion I'd expect to get for any given amount. I really didn't want to mix up a small batch and then find out later that I had enough to level the house.

IsaacKuo
2012-Aug-09, 03:37 PM
Consider this: to swing the feather you have to first move it through the air, so you are certainly applying more force than the air itself.
You almost certainly are not. Air pressure is about 100kPa, so a feather with an area of perhaps 10cm^2 experiences a force of about 100N (about 20 pounds). The thing is--this force is experienced on both sides, so air pressure is helping nearly as much as it's resisting.

What matters is the force required to stop the feather. Even if a feather doesn't have so much mass and isn't moving very fast, it still takes a significant force to stop within whatever fraction of a millimeter it penetrates the obstacle.

Swift
2012-Aug-09, 06:23 PM
I'd always wanted to make some of this stuff when I was a kid (after reading about it in some science book). I was able to look up how to do it pretty easily, actually. But I never did, because all of the documentation I could find focused on how sensitive it was, but I couldn't find anywhere that it said how big of an explosion I'd expect to get for any given amount. I really didn't want to mix up a small batch and then find out later that I had enough to level the house.
I have no data on how big an explosion you get, just some stories and my own experience.

One story I heard was of some chemistry students that made a beaker full of it, used a little for something, then left the beaker sit out to dry on some windowsill. When it dried it went off and blow out not only the window it was next to, but a significant amount of the wall around the window.

With my own involvement with making it, we too made, IIRC (this was around 1979) about 100 ml of solution. While we were making our little dipped paper squares, the Chemistry Club's faculty advisor came by and asked us what we were doing. When we told him what we had made, he was rather shocked, particularly about the quantity we had made, and made us dispose of it. We diluted it in a bigger amount of water, like several gallons, and poured that out over a gravel driveway. When it dried and you walked on the driveway, you heard little crackling sounds from the microexplosions.

NEOWatcher
2012-Aug-09, 06:39 PM
We diluted it in a bigger amount of water, like several gallons, and poured that out over a gravel driveway. When it dried and you walked on the driveway, you heard little crackling sounds from the microexplosions.
Hmm... Pop Rocks. Just not edible.

DonM435
2012-Aug-09, 07:00 PM
It's a good think I knew nothing about this stuff when I was young and reckless.

Ara Pacis
2012-Aug-09, 07:05 PM
And here my friends in HS thought they were clever making nitroglycerin and napalm.

Solfe
2012-Aug-09, 10:09 PM
And here my friends in HS thought they were clever making nitroglycerin and napalm.

I had a friend in high school "make napalm". His formulation included soap shavings, gasoline, rubbing alcohol and aspirin. I don't think he ever took a chemistry class because while it was great at removing spots and stains, it simply wouldn't catch fire.

Ivan Viehoff
2012-Aug-10, 10:43 AM
At my (high) school in the wondrous city of Croydon, some students discovered that the chemistry department had a piece of rubidium metal, and also how they could illicitly get into the chemical store area. Rubidium is the next one up after sodium and potassium, so even more explosive on contact with water than those.

So they went in before school began (as older students were routinely permitted), rigged up a long piece of plastic guttering with a bowl of water at the end, put the Rb at the top of the gutter, tipped it off and retreated rapidly. They were surprised at the violence of the explosion, requiring the immediate attendance of the fire service, though fortunately the fire proof surfaces of the chem lab were sufficient to prevent any serious damage occurring. The location where this happened was apparent through some smoke staining for many years afterwards, a cue for the chemistry teachers to tell a Precautionary Tale to future generations of students. The chemistry department also thereby discovered something that really ought to have been obvious to them, the folly of storing something like rubidium on open shelf in the chemistry store, or indeed, having more than a very small quantity of it at all.

As this was, at least in those days, a Rather Good School One Was Fortunate To Go To (in my year 12% of students went on to Oxbridge), it was a source of never ending surprise to me that about once or twice a year someone managed to get themselves expelled due to some particularly idiotic piece of criminal activity.

NEOWatcher
2012-Aug-10, 12:08 PM
This clears up some skepticism I had in one scene in The Manhatten Project (http://www.imdb.com/title/tt0091472/). (That's among an ocean of skepticism in that movie)

I didn't think that these kids could have mixed up a concoction in the science room, drop a bit of liquid on the drawer, and have it go "pop" when the drawer was shut.

swampyankee
2012-Aug-10, 12:14 PM
As this was, at least in those days, a Rather Good School One Was Fortunate To Go To (in my year 12% of students went on to Oxbridge), it was a source of never ending surprise to me that about once or twice a year someone managed to get themselves expelled due to some particularly idiotic piece of criminal activity.

Well, getting caught at some particularly idiotic piece of criminal activity. This does lead one to wonder how many students did the same sort of thing and were careful enough not to get caught. ;)

Tog
2012-Aug-10, 12:33 PM
I learned how to make this when I was about 16. The eay I learned was almost too easy to screw up. Almost. I let it sit for 15 minutes, not 24 hours. I managed to get a few to go off, but only when I was blowing on them to dry it out.

The person that taught me about it said he used put drops on his desk at work, then put drops of sugar water around those drops. When flies would come in to get the sugar, it was like stepping on little land mines.

He said he did have a prank go wrong when he blew a hole in a car tire using an amount he described as being about the size of a blob of bird "droppings." I'm assuming seagull, not sparrow.


Well, getting caught at some particularly idiotic piece of criminal activity. This does lead one to wonder how many students did the same sort of thing and were careful enough not to get caught.

Never got caught. My youthful indiscretions included breaking into the school across the street, making bombs out of gunpowder and paint bottles, and putting an explosive warhead on a model rocket that could go off in impact, or airburst. The one time we tested it, the rocket fins fell off and we missed the hill, but I'm still confident in the design.

I never did any in my school, though. You don't something where you live.

swampyankee
2012-Aug-10, 03:38 PM
I have no data on how big an explosion you get, just some stories and my own experience.

One story I heard was of some chemistry students that made a beaker full of it, used a little for something, then left the beaker sit out to dry on some windowsill. When it dried it went off and blow out not only the window it was next to, but a significant amount of the wall around the window.

With my own involvement with making it, we too made, IIRC (this was around 1979) about 100 ml of solution. While we were making our little dipped paper squares, the Chemistry Club's faculty advisor came by and asked us what we were doing. When we told him what we had made, he was rather shocked, particularly about the quantity we had made, and made us dispose of it. We diluted it in a bigger amount of water, like several gallons, and poured that out over a gravel driveway. When it dried and you walked on the driveway, you heard little crackling sounds from the microexplosions.

In college, some of the students in freshman chemistry class tried to make it. The story (probably urban legend) was that the solution spilled, and for several days walking in the lab was accompanied by loud "cracks."

Ara Pacis
2012-Aug-10, 07:25 PM
I had a friend in high school "make napalm". His formulation included soap shavings, gasoline, rubbing alcohol and aspirin. I don't think he ever took a chemistry class because while it was great at removing spots and stains, it simply wouldn't catch fire.

I wasn't there when they set it alight, but from what I'm told they were lucky not to burn down the playground.

Tom Mazanec
2012-Aug-11, 12:11 PM
How does nitrogen triiodide compare in sensitivity to chlorine azide http://en.wikipedia.org/wiki/Chlorine_azide ?

swampyankee
2012-Aug-11, 12:55 PM
How does nitrogen triiodide compare in sensitivity to chlorine azide http://en.wikipedia.org/wiki/Chlorine_azide ?

Well, you could read this (http://pipeline.corante.com/archives/2011/02/25/things_i_wont_work_with_chlorine_azide.php). He tells it very well.

peteshimmon
2012-Aug-11, 04:09 PM
I remember reading an old boy at my school
before my time was caned for making some.
He painted it on a few door handles.

Tom Mazanec
2012-Aug-11, 04:37 PM
According to Wikipedia, silver nitride is extremely sensitive to shock.