I’ve been reading a good science fiction anthology, which made me think about future technology and the limits of extensions of current technology.

How small can a chemical explosion be?

A single molecule can disintegrate, but that’s not what I’m talking about. There would need to be a shock wave passing through the material that triggers other molecules to disintegrate, but that implies some sort of confinement. How big an object would you need to get that self-perpetuating shock wave?

A follow-on from that, is how small a gun could be? 100 micron bore? 10 micron? 1 micron? Guns use the pressure of a confined gas to accelerate a chunk of matter.

one imagines you’d need to look at semi or near complete vacuums to get anything near an “explosion” when you talk about smaller and smaller releases of energy.

mollwollfumble said:

A follow-on from that, is how small a gun could be? 100 micron bore? 10 micron? 1 micron? Guns use the pressure of a confined gas to accelerate a chunk of matter.

The Van de Waals forces between a surface and a particle, or between particles themselves, increases dramatically as the particle size is reduced below 100 microns. By about 20 microns, the graph of cohesive force versus particle size is almost vertical. So I would think that somewhere in the range between 20 and 100 microns would be a limit for the bore of a gun.

What is the dividing line between physics and chemistry?

Ian said:

What is the dividing line between physics and chemistry?

chemistry is the study of change …

Dropbear said:

Ian said:

What is the dividing line between physics and chemistry?

chemistry is the study of change …

What about an isotope changing by radioactive decay?

morrie said:

mollwollfumble said:

A follow-on from that, is how small a gun could be? 100 micron bore? 10 micron? 1 micron? Guns use the pressure of a confined gas to accelerate a chunk of matter.

The Van de Waals forces between a surface and a particle, or between particles themselves, increases dramatically as the particle size is reduced below 100 microns. By about 20 microns, the graph of cohesive force versus particle size is almost vertical. So I would think that somewhere in the range between 20 and 100 microns would be a limit for the bore of a gun.

That’s an excellent point, morrie, thanks. I had been wondering whether it might be possible to fire a single atom of argon down the bore of a carbon nanotube as the small-scale limit of a gun, given that a perfect carbon nanotube is exceedingly smooth having no protuberances or loose covalent bonding opportunities. But I hadn’t been thinking about Van de Waals forces.

> “vacuum”

Yes, that’s what I had in mind.

> What is the dividing line between physics and chemistry?

They overlap at the level of atomic theory, electron orbitals and all that. Thermodynamics tends to be allocated to chemistry, as does crystallography. Covalently and ionically bonded molecules are included in chemistry. The metallic bond overlaps physics and chemistry, as does superconductors. Semiconductors are assigned to physics. Aggregates of molecules that satisfy Newton’s equations get assigned to physics.

Actually, I ought to have a much better answer than that. Go to Nature seed map of science and zoom in on the text in the area between “Physical Chemistry” and “Applied Physics”. You’ll find nanotubes just on the “physical chemistry” side of the boundary, with corrosion just slightly further towards “physical chemistry”. The dividing line is very close to semiconductors. Slightly further towards “applied physics” are pzt films and ceramics, with nanoparticles well into the field of applied physics.

Dropbear said:

Ian said:

What is the dividing line between physics and chemistry?

chemistry is the study of change …

thanks Walt

mollwollfumble said:

> What is the dividing line between physics and chemistry?

They overlap at the level of atomic theory, electron orbitals and all that. Thermodynamics tends to be allocated to chemistry, as does crystallography. Covalently and ionically bonded molecules are included in chemistry. The metallic bond overlaps physics and chemistry, as does superconductors. Semiconductors are assigned to physics. Aggregates of molecules that satisfy Newton’s equations get assigned to physics.

Actually, I ought to have a much better answer than that. Go to Nature seed map of science and zoom in on the text in the area between “Physical Chemistry” and “Applied Physics”. You’ll find nanotubes just on the “physical chemistry” side of the boundary, with corrosion just slightly further towards “physical chemistry”. The dividing line is very close to semiconductors. Slightly further towards “applied physics” are pzt films and ceramics, with nanoparticles well into the field of applied physics.

Ah. Excellent molly. I’ll study it later on (meanwhile I’m getting on with an early FNDC – now open)

explosions as i’m aware are about a rapid burning in a front that spreads through a material

its not about confinement but rather how much gas you can produce in the shortest possible time

a “proper” explosive doesn’t necessarily need confinement as such but will happily explode without a container.

wookiemeister said:

explosions as i’m aware are about a rapid burning in a front that spreads through a material
its not about confinement but rather how much gas you can produce in the shortest possible time
a “proper” explosive doesn’t necessarily need confinement as such but will happily explode without a container.

Thanks for that. I’m looking into nitrogen iodide NI3.NH3. According to Meldrum 1940 nitrogen iodide has several interesting properties. One is that if dried in vacuum at temperatures at or above -11 Celsius it explodes spontaneously as soon as it is dry. If dried at room temperature it can sometimes be set off by the touch of a feather. Explosion can be suppressed at temperatures of -12.5 Celsius and below, or at higher temperatures under an ammonia atmosphere at sufficient pressure.

Individual crystals of exploding nitrogen iodide in their experiment had a mean radius of 2 microns. That would truly be a micro-explosion, and there was no attempt to try even smaller crystals so that gives us an upper limit on how small an explosion of nitrogen iodide can be. “The reaction is very probably limited to the surfaces of crystals, contrary to Roginski’s suggestion”

As you pointed out, the explosion didn’t need confinement.

> If dried at room temperature …

Oops. Should have said:

“If dried in air at room temperature, pressure and relative humidity …

i thought high explosives were a shock wave travelling through the material and causing a “chain reaction”. could be wrong.

what is being suppressed if the explosion can be prevented with an ammonia atmosphere of sufficient pressure?

>>i thought high explosives were a shock wave travelling through the material and causing a “chain reaction”. could be wrong.<<

Yes. A detonation is a self sustaining wave as against a deflagration which is more a rapid burning process.

ie. blackpowder velocity of expansion at around 300 metres per second as against the slowest detonation as about 2000 metres per second to around 14000 metres per second for conventional High explosives.

i was hoping you would appear BU. in a puff of purple smoke. (iodine based maybe)

;-)

Boris said:

i was hoping you would appear BU. in a puff of purple smoke. (iodine based maybe)

;-)

You’re probably the only one who was hoping that!

I thought you might, Boris. However, you are correct. Little smidgeons like that are propelants & nothing more.

Riff-in-Thyme said:

what is being suppressed if the explosion can be prevented with an ammonia atmosphere of sufficient pressure?

What it seems to be is that the pure NI3 is immediately explosive, but when it has ammonia NH3 molecules on the surface of the crystal these tend to suppress the ignition until enough ammonia evaporates off. In an ammonia atmosphere the evaporation of the surface ammonia is suppressed, so that tends to suppress ignition.

You’re probably the only one who was hoping that!

waves to Shebs. :-)

mollwollfumble said:

Riff-in-Thyme said:

what is being suppressed if the explosion can be prevented with an ammonia atmosphere of sufficient pressure?

What it seems to be is that the pure NI3 is immediately explosive, but when it has ammonia NH3 molecules on the surface of the crystal these tend to suppress the ignition until enough ammonia evaporates off. In an ammonia atmosphere the evaporation of the surface ammonia is suppressed, so that tends to suppress ignition.

fair enuff

Look if you guys really need to know about this style of thing, there’s a bunch of stuff that those of us in the know would rather not know about. Start here….

http://pipeline.corante.com/archives/things_i_wont_work_with/

This gentleman is an Organic Chemist & as such is better qualified than me on things you should not work with.

:-)

a red light starts flashing in the nsa hq.

Boris said:

a red light starts flashing in the nsa hq.

ssssh.

In a research lab that I once worked in, they produced explosions of precisely controlled magnitude by passing an electric current through a piece of wire. The electrical energy was accumulated in a large bank of capacitors and the discharge happened in an instant. Using this technique, they could shatter pieces of rock and concrete. The wire was stretched inside a hole drilled in the rock. The electrical current caused rapid vaporisation of the wire.

So explosions don’t have to be purely chemical in origin.

Similarly, I intense laser bursts are used to cause explosions by rapid vaporisation of matter, in for example in laser ablation.

So, neglecting the typos, if you confined the right sort of material inside the right sort of container, you might be able to induce an explosion by subjecting the material to an intense burst of electromagnetic radiation, such as microwaves, perhaps.

morrie said:

So, neglecting the typos, if you confined the right sort of material inside the right sort of container, you might be able to induce an explosion by subjecting the material to an intense burst of electromagnetic radiation, such as microwaves, perhaps.

a minaturization of what we know already occurs. confine the burst.

Do we need to define ‘explosion’ before arguments about moving goal posts breaks out?

Stealth said:

Do we need to define ‘explosion’ before arguments about moving goal posts breaks out?

or implodes?

Bulgarian Umbrella said:

You’re probably the only one who was hoping that!

waves to Shebs. :-)

Who TF is Shebs?

And what would be the effect of placing one of these micro-explosions under one’s favourite public figure?

Ian said:

And what would be the effect of placing one of these micro-explosions under one’s favourite public figure?

none. there is nothing here to dob anything with.

dob?

roughbarked said:

Ian said:

And what would be the effect of placing one of these micro-explosions under one’s favourite public figure?

none. there is nothing here to dob anything with.

So this is gibberish?

mollwollfumble said:

> What is the dividing line between physics and chemistry?

They overlap at the level of atomic theory, electron orbitals and all that. Thermodynamics tends to be allocated to chemistry, as does crystallography. Covalently and ionically bonded molecules are included in chemistry. The metallic bond overlaps physics and chemistry, as does superconductors. Semiconductors are assigned to physics. Aggregates of molecules that satisfy Newton’s equations get assigned to physics.

Actually, I ought to have a much better answer than that. Go to Nature seed map of science and zoom in on the text in the area between “Physical Chemistry” and “Applied Physics”. You’ll find nanotubes just on the “physical chemistry” side of the boundary, with corrosion just slightly further towards “physical chemistry”. The dividing line is very close to semiconductors. Slightly further towards “applied physics” are pzt films and ceramics, with nanoparticles well into the field of applied physics.

That’s fascinating and very informative as is the detailed (if somewhat hard to read) map.

Thanks molly

Ian said:

And what would be the effect of placing one of these micro-explosions under one’s favourite public figure?

I suspect that all you would get is a small gas bubble, harmless if the explosive was ingested, inhaled, injected into muscle or skin contact. It would sting a bit. Potentially dangerous if in the bloodstream or in a critical part of an organ such as the optic nerve.

On the other hand, a million micro-explosions going off simultaneously in one’s favourite public figure could do a lot of damage.