As a fertiliser, ammonium nitrate is by necessity readily available in bulk.
Unfortunately however this makes it ideal for other, more nefarious purposes (truck bombs, but you figured that out already).
I suggest that an additional stage be added to the manufacturing process to make AN useless as an explosive, without unduly affecting its agricultural properties.
Before crystallisation, tiny plastic micro-bubbles containing a flame retardent are added. For normal use, these micro-bubbles sit in the soil doing nothing (ideally of course both the bubbles and their contents would be bio-degradable).
If however the AN is ignited in bulk form, the plastic bubbles melt, releasing the retardent, and suppressing the reaction before it gets started. The ideal retardent would have been BCF (as once used in fire extinguishers); as this catalytically interferes with the process of burning, so would be effective even with 'self-oxidising' nitrates but without adding too much extra bulk.
(more incentive for someone to develop ozone-friendly BCF?)
I realise of course that this AN could still be re-processed to its original form; the idea is that the trouble & effort of dissolving several hundred kilos of AN, filtering it, and drying it out without blowing himself up would be quite a deterrent to the common or garden terrorist.-- philmckraken, Oct 17 2004 New Scientist: water-soluble, oil-repellent coating http://www.newscien...s.jsp?id=ns99994782Similar, but coat the fertilizer, rather than mix with retardant. [jutta, Oct 17 2004] Deflagration, Explosion and Detonation http://guns.connect.fi/gow/nitro.htmlA decent article defining the differences in the rates of exothermic reaction. [bristolz, Oct 19 2004] Couldn't the plastic micro-bubbles potentially be filtered out of the fertilizer, restoring it to its former explosive nature? I envisage some sort of electrostatic sorting process whereby the plastic bubbles are statically charged and selectively removed. Otherwise, this idea is tops.-- vigilante, Oct 17 2004 There must be some biologically inert chemical or otherwise means of controlling this stuff's properties.
Perhaps a licensing approach would reduce its availability?-- RayfordSteele, Oct 18 2004 [phil] Haven't you been listening to Mr Heston, the Republicans and the NRA? It's not the ammonium nitrate that kills......, and your constitution guarantees the right of everyone to make bombs out of it and toss the bombs around defending themselves........ Please pay closer attention in future... :)-- ConsulFlaminicus, Oct 18 2004 More interesting would be if someone could find a means of making cellulose nitrate non-flammable without damaging its physical structure. Some old movie films are priceless, but simultaneously dangerous. If there were a way to treat the nitrate without damaging it, that could be very useful.-- supercat, Oct 18 2004 Great link, thanks [Jutta]; I hadn't even realised that there was already research into this... but I suppose it's obvious really.
[vigilante], my idea would involve introducing the micro-bubbles to the AN while in aqueous solution, they would then act as nucleation points so the AN crystallises around them. To 'purify' the AN would involve re-dissolving it as I mentioned, or alternatively grinding it to a powder... which would make it very liable to a 'flour bomb' type explosion as per [UnaBomber]...er, [UnaBubba] (you seem to know an awful lot about this sort of thing...???)
I had also thought about tagging the AN as in [Jutta]'s link (but using trace amounts of various different radioactive isotopes), but this is useful only in identifying the perpetrator after an attack. Terrorists seem quite happy to claim responsibilty for their attacks...
Controlling & regulating the sale and distribution of AN is another approach (which is what some countries are apparently already doing). I worry though that the terrorist response would be simply to hijack a truckload of the stuff, and shoot the driver...like they would if it was a truckload of dynamite or other 'proper' explosive.
Having said all of that, [CF] is quite right of course; who am I to infringe upon other people's constitutional rights? what was I thinking...
As for [supercat]'s problem with old film stock... I dunno, any chemists out there with bright ideas? Maybe freezing the films cryonics-style to halt the degradation, so that they can be saved sometime in the future... (let's be honest, this has much greater chance of success than reviving old people's dead frozen heads...)-- philmckraken, Oct 18 2004 I don't like the idea of eating food fertilized with fire retardent.
I also don't like the idea of increasing the cost of food for everyone just to make it slightly more difficult for someone to make an explosive. It is impossible to make it impossible for people to build weapons. Making it difficult is sometimes worthwile, but only if the benefit is much greater than the cost.-- scad mientist, Oct 18 2004 Deflagration, explosions and detonations are all different behaviors. <link>-- bristolz, Oct 19 2004 //It is impossible to make it impossible for people to build weapons//..quite so [scad]. For example, one could board a typical airliner completely unarmed and with a few hours industrious activity assemble an arsenal of tools and weapons including garottes, stilettos, molotov cocktails, clubs/cudgels, maces, pikes/spears, flame throwers ...just from material found in the passenger cabin.
Persons skilled in the chemical arts...[edited] well, let's not give them any clues here.
(Disclosure : the author has disposed of all airline shares)-- ConsulFlaminicus, Oct 19 2004 If it doesn't explode, it no longer is Ammo, is it?-- neelandan, Oct 19 2004 Are you sure that this will have enough time for the plastic spheres to melt? Will they release fast enough to do more than decrease the yeild?
Oh - Isn't AN quite stable, making procesing easy? (well, until you put in a sensitizer...)-- my-nep, Oct 19 2004 First, you wouldn't want to put any plastic in with AN; on exposure to heat, that will surely turn it to ANFO just like the wax anti-caking compound did at Texas City and Brest, France in the years after WWII. These two multi KT explosions rank in the top 10 of non nuclear man-made blasts.
What sort-of works is mixed fertilizer containing ammonium nitrate and ammonium sulfate. This is OK as long as the mixture is even and the %age of AN is not too high (less than 60%).
One still has to be careful! The first recorded AN disaster, at Oppau, Germany 21 may 1921 killed over 500 persons. It involved an estimated 500 tons of overly rich mix in a huge storage pile that was some 40,000 tons. If it had all gone, it would have exceeded a lot of A-bomb detonations.-- TD3, Oct 29 2004 random, halfbakery