Sciencemadness Discussion Board

Acid-base 'explosives'

overseer - 19-6-2005 at 12:06

From what I've seen, most of the participants of these forums discuss energetic reactions of those substances usually considered as "explosives." These are either single molecules containing both the oxidizing and parts to be reduced, or fuel/oxidizer mixtures. The fuel/oxidizer mixtures usually burn slower, and thus constitute "low order explosives." Such explosives, like black powder, can burn faster if ignited in a confined space, owing to the fact that the reaction rate increases as heat is trapped inside (and hence the particles move faster, colliding more often) and the pressure increases (liberated gaseous products). This also means that low order explosives can be just as destructive as their high-order counterparts, if packed in tight and strong containers. This part, I believe, all of You know.

Some of You may have heard about explosions produced my means of an electric discharge of a large capacitor bank through a small quantity of water, in a sealed container. Weapons were developed, where the projectile is pushed not by means of gases evolved from burning of a propellant explosive, but by water vapor developed during the discharge of a capacitor through water. Info on this, I believe, can be found on the web. If the capacity and voltage rating of the capacitor bank are sufficiently high, the energy W=C*U^2/2 being sufficient to evaporate water, what happens in a sealed container with this water is the same as if some explosive burned: the energy was released locally, causing the expansion of the gas evolved (in this case, no chemical reaction, only phase change of water into water vapor). This closely resembles an explosion of a steam tank.

Excuse me for being so thorough with the introduction; now for the reason I'm writing this. I recall of a lab accident that happened a few years ago, where a few drops of concentrated NaOH solution inadvertently ended up in a flask containing a residue of 80% H2SO4. These few drops reacted violently (as everyone would expect) releasing heat and vapor that caused the flask to shatter with a "bang." The "bang" was not very loud, but nevertheless...

Now, this prompted me to think whether this mechanism could be employed to create an explosive device. Suppose one would take two small plastic bags and heat-seal some concentrated NaOH solution in one, and some conc. H2SO4(aq) in the other. Put these two bags into close contact within a sealed plastic tube with strong walls (that could withstand some pressure) and put some primary explosive (a detonator) in between. What would happen upon ignition?

My guess would be that the two chemicals would mix mostly in vapor phase, releasing lots of heat and water vapor, and in the end causing the casing to blow. The water vapor thus released would do the same work as the gas released in "conventional" explosions, thus such a device should be able to crack rock like conventional explosive-based ones. On the other hand, it would create no harmful waste by-products, and would be absolutely safe to transport in the form of separate acids and bases. It should be a simple matter to calculate the heat release of such a reaction from appropriate tables and equate this to the heat required to evaporate all the water, for maximum yield (with a safety margin of excess energy, of course).

My question here is, did someone try this before and what were the results? Obviously, metal containers would be a poor choice for experiments, as they would react with (accidentally) spilled acid (or even bases, if the metal was aluminum). Some form of hard and thick plastic tubing should do best, so it could be machined (ABS?). The basic "trick" here would be to increase reaction rate by confining the space and ensuring the thick vessel walls would hold until the reaction is nearly complete. Only a high enough reaction rate could simulate conventional low order explosives in this manner. However, safety may be compromised in case the thin plastic bags begin to leak (multiple stacked bags, one in another?) Comments? Suggestions?

vulture - 19-6-2005 at 12:36

What you are basically suggesting is a crofty bomb from NaOH and H2SO4 with a detonator? :o

[Edited on 19-6-2005 by vulture]

kyanite - 19-6-2005 at 13:15

Very, unconventional. This sub-category(or w/e) IS called energetic materials, and I suppose this is an energetic mix.
What I can see making the reaction less 'energetic' would be the speed of the reaction. Sulfuric acid and NaOH would DEFINATLY release a lot of energy as heat and water vapour boiled by the heat, creating a lot of pressure, but in my oppinion, this would be 'low order' as the reaction still isnt at the molecular level.
Analogy would be the big jump and difference in 'energetic-ness' between a burning mix like gunpowder and a powerful-shockwave forming-extremly quick detonation of, say TNT.

Intersting because it's unconventional, but still seems kind of kewlish to me.

Perchloric Acid and purposly pretty much anything would be something I'd like to see though.:o

[Edited on 19-6-2005 by kyanite]

my nootloss - 19-6-2005 at 20:15

If I can remember correctly, some years ago a couple of kids where running around with (thick) glass bottles with baking soda and vinegar. And thus succeeded in severely maiming themselves or someone (I think it was themselves).
This is what gave me the idea to put the both of these chemicals in those black photo cans, some how I got it so that when I would shake them they would mix (well these being much less powerful then the things above I had some time to walk away). After perfecting my little things I decided that I would walk up to the girls who lived down the street and talk them into holding these things as I walked away… Those girls never did talk to me again. Well to tell you the truth I think they moved, but you get the point.

Axt - 19-6-2005 at 23:27

umm. yeh. Ca(OCl)2 & brake fluid anyone? Dry ice in a bottle? essentually the same effect.

In the broader context of steam explosions you may be interested in molten metal + water explosions. It being a somewhat novel approach to making a boom. Search google for "molten metal water explosion" or words to that effect and it will pull up many instances where a violent explosion has resulted from contact of a molten metal with water.

Also try patent <a href="http://www.freepatentsonline.com/patents/us/437/4372213/4372213.pdf">US4372213</a>, detailing a thermite/intermetallic mixture of Ni/Al/CuO used to initiate a MMW explosion.

Also patent <a href="http://www.freepatentsonline.com/patents/us/521/5212343/5212343.pdf">US5212343</a>, which details with good examples, the effect of titanium/boron intermetallic explosions underwater.

"A phenomenon of considerable industrial importance in recent years is the vapor explosion, often referred to as a thermal or steam explosion. This phenomenon results from the extremely rapid heat transfer from hot liquid (e.g., molten metal) to cold liquid (e.g., water) when the two are contacted together. Sporadic explosions resulting from this phenomenon have been responsible for loss of life and property in industry for a number of years, and efforts have been made to understand the extreme violence of these interactions. It is not presently known exactly how these explosions are initiated. However, resultant effects of these interactions are dramatic, and substantial amounts of energy are released during such explosions."

overseer - 20-6-2005 at 06:42

to Vulture:
Yes, that is basically what I proposed. But I don't recommend anyone building it by just packing plastic bags in a tube, as the bags may leak. I plan to test them by immersing in indicator solutions and squeezing them a bit to check whether they would give way. They should be made of thick plastic and heat-sealed, and I'm considering separate acid and base containing tubes, that would snap-on together, prior to use. But first, I need to complete the tests in a semi-open tube with a special weighed piston, to work out the thermodynamics. The major question is whether some unexpected (or nonlinear) effects would arise if larger amounts of reagents are used. The reaction rate may slow down if too much reactants are used, or some products other than salt and water may be created under such extreme conditions (?)

to Kyanite:
I believe I mentioned the reaction rate, which should increase as the released heat and pressure build up in a confined space, in a quick (and thus adiabatic) process. Given the energy gain, the reaction rate should reach levels comparable to those of standard low order explosives.
Comparing this to a detonation was not my intention. A detonation, as produced by a high-order explosive, is characterized by a high detonation velocity. Therefore, gases are being produced that compress the surrounding air at a higher rate than the speed of sound, so the energy is released, but cannot get away. A "shockwave" results, which is a "wall" of highly compressed air, that moves away hemispherically from the detonation site, and releases energy upon contact with other surfaces (that is, when it encounters a large enough impedance difference for sound waves). Thus, a basic result of a detonation is a shockwave that expands and can cause damage at a location distant from where the detonation itself took place. Actually, it's a bit more complicated than this, but I believe this should suffice. My goal is to produce "low order" explosions, that can do useful work in situ. If placed in a hole drilled in a rock or concrete, the device should be able to crack it, as it happens when explosives are used in quarries or in bringing down old buildings. I do not intend to make firecrackers or malicious jokes. Perchloric acid / fuel mixture would undoubtedly do the job, but the basic idea was to avoid unstable chemicals and make the energetic reaction very safe and very cheap, the ingredients being unable to detonate by themselves, and useless per se, if stolen. Anyway, I am grateful for Your opinion.

to My nootloss:
The baking soda / vinegar reactions are classics for making "chemical rockets" without fire or explosives, and can be found in numerous places on the web. Mostly in children science books, or in the form of "kits" for amusement. However, releasing carbon dioxide cannot do a lot of useful work, since as the pressure rises, the reaction would slow down and the H2CO3 would cease to break down into CO2 and H2O. All one would get is a slightly increased pressure due to CO2 evolved. Enough to crack a small bottle and injure oneself, but far from enough to do some useful work as an explosive. I urge those inexperienced to never try any energetic reaction in glass bottles, as these not only cause severe injury by creating sharp fragments, but the small transparent fragments are also hard to detect in the tissue by a surgeon.
Evolving a gas in a confined space is *not* analogous to this reaction, since there's no heat loss involved. A strong metal bottle can withstand the pressure, as indeed is the case when storing gases in them. Conversely, releasing enough energy can do a lot of work: just remember the old locomotives that ran on steam – the work was enough to pull whole trains. Now imagine all that energy released in a single blast.

to Axt:
Thank You for the references, I'm going to look them up. I appreciate all relevant references, even remote ones. Though there is a major difference here: processes involving things such as molten metal or large capacitor banks are complicated, dangerous and costly. The idea here is to utilize super-simple and cheap, widely available chemicals. A possible drawback may be the offset cost of transporting a quantity of acid and base, but that is yet to be determined. In any case, the vapor explosion citation sounds encouraging, thanks.

Tonguska Event

Rosco Bodine - 20-6-2005 at 08:11

Basically the flash boiling of ice to steam is what occurred when a comet impacted the earths atmosphere above Tonguska Siberia , resulting in an explosion having the energy release comparable to a very large nuclear explosion , hundreds of megatons yield , and flattening hundreds of square miles of forest . Some high altitude impacts of snowballs from space are regularly detected by satellite imagery as anomalous pockets of hot water vapor . Get a big enough snowball coming in at hypervelocity , and then you get another Tonguska Event .

However the following scenario is not exactly accurate .

"This also means that low order explosives can be just as destructive as their high-order counterparts, if packed in tight and strong containers. This part, I believe, all of You know."

Molecular explosives , high explosives which require no confinement for their energy release , are going to be much more destructive pound for pound than
low order explosives , due to the actual detonation of the energetic material producing a more rapid , higher kinetic energy shockwave , than anything typical
from a combustion based pressure rupture of a container resulting in an explosion . Explosions and detonations are not really comparable , except for those extreme situations where an external kinetic energy component is supplied to multiply the usual effect .

[Edited on 20-6-2005 by Rosco Bodine]

Marvin - 20-6-2005 at 11:51

Its worth remembering that pyrotechnic mixtures can produce a lot more energy weight for weight than traditional high explosives. They certainly have the potential to outperform but the circumstances and scales are so different.

The critical question for me is 'Where does the energy come from and how dense is this source?'. Molten metal and current pulses through water are just delivery mechanisms and as far as acid base reactions go I think these sound rather poor performers.

KemiRockarFett - 20-6-2005 at 12:25

An thick walled steel container and two separeted volumes of ammonia gas compressed in one of these and HClO3 so higly concentrated as you dare in an other volume. Than let 50 g RDX fuse them together :)
Good waste of nice chemicals to get an worseless explosion but it will work.

In ordinary neutralisations dont use NaOH use ammonia(aq) it will give more energy !

my nootloss - 20-6-2005 at 23:26

Well since we are on the topic of water making explosions I am going to further misguide our train of thought by tell you guys to look up some thing, Well you know how there is someone out there always trying to make an atom got as fast as the speed of light? Well now look up how they stop that atom at the end of the track, I will give you a hint it involves a lot of water and a Cu block ... ;)

budullewraagh - 21-6-2005 at 05:13

i keep hearing of oxidizing acids being used. it's important to remember that the oxidizing power of these acids will actually not do anything to the enthalpy change in the system, unless they decompose, which, mind you would be explosive in nature. important factors include the strength of the acid (dissociation constant), in addition to the maximum concentration (solubility) of the acid.

sulfuric acid can get up to reaaaaaly high concentrations (high 90s in %) before fuming away the anhydride. perchloric acid cannot get that high (85% or so is just about the max, and even then it fumes quite a bit).

so if we want to consider the most "explosive" mixture, our acid will be conc H2SO4. now as for a base, cesium hydroxide would be beastly, and is soluble in 0.25 parts water. thus, 4g CsOH/1g H2O.

4(132.9+16+1)/(4(132.9+16+1)+(18))=0.97
so we can get CsOH to 97% conc.
NH3 cannot get near that concentration.

anhydrous NH3, on the other hand, is at 100%, but it wouldn't result in the same extreme enthalpy change as 97% CsOH would.

this brings up another thought; what about anhydrides?
SO3+NH3 will not react, will they? perhaps they would work H2O+N2+S. anyone know? if not, a water molecule would be useful, but im not sure i can see the above reaction occurring. i could imagine this fuming liquidy goodness to be a formidable mixture. imagine the enthalpy change from addition of water. first there is the energy release when the components are dissolved, then immediately the strong acid/base reaction.

unfortunately, i believe CsOH and SO3 would react.

now if we want to go to the even more unreasonable, we can consider HSbF6 and CsOH, but that's another story.

[Edited on 21-6-2005 by budullewraagh]

Rosco Bodine - 21-6-2005 at 09:48

Certain ternary or quaternary mixtures might also have some interesting hypergolic effects . Thinking of sudden
mixtures of lithium borohydride with fluorine and N2O4 , moderating the reaction with a stream of hydrazine :D

overseer - 21-6-2005 at 10:14

I see there is increasing understanding in why H2SO4 is preferable to other acids. Correct, the enthalpy change is the key, but we also need to do mechanical work in the end. It's not just about releasing energy, we need water to transfer this energy to. The water evaporates, the vapor expands, and so part of the energy can be utilized to do mechanical work. This is, in my thinking, why it's not so important to dissolve as much of the acid as possible in as little water as possible: we need the water vapor for the physical part of the task.

Some participants have expressed concern about the detonation velocity and kinetic energy. Let us not mix things up. There are extremely energetic reactions, such as nuclear decay processes, that produce kinetic energies on the order of MeVs. Yet, the slow reaction rate makes a typical barely enriched nuclear fuel just capable of heating up some water. The intrinsically high reaction rates of high-order explosives make them capable of producing a shockwave without confinement, but this has nothing to do with the energy released (enthalpy change) in a single active collision. Generally, it is true that high order explosives pack a strong blow per unit mass, but this is not what I meant when I stated that "low order explosives can be just as destructive as their high-order counterparts." I simply wanted to point out that, in many cases, the job usually done with a high-order explosive can also be done with a sufficient (if larger) amount of a low order one.

Suppose You want to do a job, say mail something to a friend. Do You really care if the package travels by train or by plane? No, if delivery times are the same, and the package comes undamaged in both cases. All You would care about in such a situation is which alternative costs less. And this is what I'm talking about : industrial (low) purity NaOH is, generally, the cheapest chemical there is. Its chemical properties aside, ammonia is more expensive, and more hazardous for transport – if spilled, it leaves as gaseous NH3 (hard to contain) and diffuses around, causing serious health problems. And it stinks a long way! :) Perhaps some other substances would do a better job in terms of deltaH, but I dare not inquire about the price of a volume of Cs compounds. The idea is always to do the job for as low a price as possible. NaOH and H2SO4 are among the few initial products in the chemical industry – other products are made from them. Thus, their price is as low as it gets, esp. considering they need not be purified for this purpose.

The strong container is not there just to produce a shockwave once it gives way, and certainly not to help produce a loud report. It is mostly there to promote the reaction rate and ensure the reaction is nearly complete before the blast. So, when inserted, say, in a hole bored in a rock, once the container bursts, the water vapor should be able to do the work of pushing against the rock forcefully enough to crack it. If the rock cracks, the job is done. And if the force can be as large as those we see pushing heavy passenger aircraft every day without their engines bursting, the vapor should be able to do the job. I believe the most important thing is to realize what Budullewraagh realized – there need not be a fuel/oxidizer burning mixture to produce an explosive result. And what I deem important in addition, is that the total energy release (more precisely, a part of it that takes the form of mechanical work) is what needs to be maximized in order to make this effective. The "speed" of explosion needs not be higher than just requred for the water vapor to be prevented from escaping the borehole before cracking the rock (if that's the goal).

Someone also mentioned the energy content, i.e. how "concentrated" the energy is. Yes, it is not very concentrated in this concept, but it need not be. If both can do the same job, one is better advised to use much more super-cheap chemicals, than just a bit of an ultra-expensive one. Of course, in some applications, highly packed energy cannot be substituted.

Anyhow, the preliminary experiments in an open-end tube have shown promising results, but I am still not ready to conduct a field test. I believe a good starting point could be to drill a hole in a wooden block and make an attempt to detonate the device inside. Harder materials would come later...

Rosco Bodine - 21-6-2005 at 10:58

If you just want to crack rock using the
" power " of phase changed water , it would be more efficient to freeze the water in the bore hole and let the expansion pressure of the ice crack the rock .

But when it comes to the shattering of rock or any other target , you can't get away from kinetics , applying the greatest force in the shortest time , for massive disruption of the target structure .

How can I split that bloody rock ?

Lambda - 21-6-2005 at 21:44

Nhaa, liquids and gases are mobile. Depending on the speed of this mobility, you will get pressure build up on the surroundings. If the speed of induction is low, then you will have to go for good tampering. How can good tampering be avoided ?, simple, make the fluide state go down. Einstein knew this, for he actually worked on mud. yes mud, he had a question to answere. Why is it, when you walk on sand on the seabed or on dry sand do you sink so deep, and on semi-wet sand, do you get so much resistance ?. All my books are still in my removal boxes, so I can't show you this equasion of proof. But you get the idee, get the mobility down by making use of loss of mobillity. Then go for expansion, and your pressures will skyrocket, without oosing out of your rock boorhole. What will expand then ?, well go for CaO (calcium oxide), make it semi-wet with water, and what do you get, yes Ca(OH)2 (calcium hydroxide). And quess what, CaO has expanded to a much greater volume of Ca(OH)2. How can this be used ?, simple, just put a perforated plastic tube of CaO snugfitting in your rock boorhole, that has previousely been dipped in a bucket of water. Go and drink a cup of tea, as to sellebrate all your efforts in drilling this borehole and wait a few hours. Phone the truck and tractor guys and tell them that they can come and pick up the split rock chunks. Even the Egyptians knew, that if you put drywood in a borehole, wet it, that you only have to wait untill expansion has done it's work and your rock will be splt. I am sorry for sounding so semi-scientific, but I think you all have got the idee.
Quote:
Madness, is a primer for inventivity !

Moving parts, maintainance, complication and expence

Lambda - 21-6-2005 at 22:15

Rosco Bodine, you are right about the kinetics that are an absolute must, if shatering is required.

Using water to expand will allso work. But this array is cumbersome and complicated. You need freezing equipment, electrics, combustion engins, powersupplies, cooling gasses, pipings, or what ever combination deemd suitible. Equipment wares out, needs maintainance etc. If seald, CaO can be kept indeffinitly, is cheap, and only two components are needed. You can get to places, were heavy or big equipment may be problematic. Multi-borehole expansion, needs multi-cooling elements and long piping.

Marvin - 22-6-2005 at 07:03

overseer,

Some bad ideas, you make the rock the container for the low explosive, you don't add a casing. Also adding extra water is counter productive. Take Al/LOX, officially this produces no gas, the shock comes from some of the vapourised oxygen, but if you add additional liquid oxygen, or water you end up with a larger mass of gas doing less work, not more. The same energy into twice as much fixed gas leads to half the temperature and the same pressure, but you lose energy when you change phase. Whats worse is with the extra material the energy density is a lot less.

Roscoe,

I see what you are saying about high explosives being better for blasting, but often for a single charge you get more damage with a 'less locally acting' low order explosive. Where a charge of blackpowder might get you a large volume of gravel from a particular rock, a similar amount of a very brisant explosive could get you a smaller volume of rock turned into dust.

Duration of force

Lambda - 22-6-2005 at 08:49

Truely so Marvin, the heaving effect on mass acceleration is in this aspect crucial. Specially when dealing with bulky slowmoving material, where the duration of force gets the motion going.

overseer - 23-6-2005 at 05:35

If I didn't know better, I'd say the prevailing scepticism about this acid-base scheme produced negative energy that caused the first field test to fail :) Of course, there is a more rational explanation.

First off, let me begin with an account of the results of the first field test, which was an ignominious failure. The "two bag and a pipe device" did explode, but with a feeble force. The examination of the remains revealed that most of the acid and base did not react at all, but the middle region (where the Hg-fulminate based detonator was placed and where the plastic pipe cracked) was covered with whitish and grayish-metallic deposits. The obvious conclusion is that the vapor developed in the middle region, actually shielded the rest of acid and base from coming into contact.

Although unsuccessful, the test proved two things: first, even a thick plastic container can't hold against the force buildup from inside, i.e. a stronger material is required. Second, the device needs to be configured in a more complex manner in order to ensure the two chemicals mix together as homogenously as possible, when the device goes off. The most important issue that I did not anticipate was, in fact, the most obvious difference between any conventional explosive and this one. In any conventional explosive, the fuel and oxidizing parts are pre-mixed intimately together, be it on a molecular level or as a physical mixture of some fuel and oxidizing agent.

Well, this means that the price has to be paid in the complexity of the device configuration. Perhaps stacking many smaller bags containg acid and base alternately, one after another, in a pipe, and using a detonator in a form resembling a bullet (that would fire a projectile rupturing all the bags quickly, upon initiation)... To put it simply, basically it can work, but it won't work and remain cheap and simple at the same time.

12AX7 - 23-6-2005 at 11:31

Concentric ring pouches may also work well given a detonator in the center.

Tim

verode - 29-3-2006 at 01:06

Quote:
Originally posted by Rosco Bodine
Certain ternary or quaternary mixtures might also have some interesting hypergolic effects . Thinking of sudden
mixtures of lithium borohydride with fluorine and N2O4 , moderating the reaction with a stream of hydrazine :D

PHILOU Zrealone - 30-3-2006 at 10:03

NH3 + SO3 --> HO-SO2-NH2 and further NH4-O-SO2-NH2
So sulfamic acid and ammonium sulfamate.

The best kind of mixes would be
Metal oxyde and acid anhydride...

Of course with already explosive reactants you win in speed of reaction.

Li2O as a base and + Mn2O7 as the acid (hell dangerous!)

Or SnO2 with Cl2O7...
etc

JustMe - 30-3-2006 at 18:41

Lot of interesting stuff here, unconventionally speaking. Just want to step back to my variant on the vinegar/baking soda "bomb."

Many, many moons ago (when a young person could walk into a chemical supply house and buy almost anything) was when I was a chemistry hobbiest. Ah, those where the days (late 1960's).

But even a hobbiest likes to impress people sometimes, and so I made my little bombs (mind you, I was not into explosives at all, but was asked to show how to make one). So I made little pressure bombs with different ingredients... Hydrochloric Acid and Aluminum foil, and, foolishly, glass bottles. Mix ingredients, seal tightly and run! I lived on the waterfront and even made one weighted so as to sink into the bay (depth about 40 feet) and waited for the burst of bubbles.

Not really complicated, dangerous to be nearby, and a satisfying bang.

I still remember my first and second experiments... first was making hydrogen (of course), zinc coil and hydrochloric acid, but the second was ambitious - Bromine. Back then hobby shops sold Sodium Bromide, Manganese Dioxide and lots of other goodies. Mix these with battery acid (before I got around to buying concentrated sulfuric acid at the chemical supply company), warm and there you have it, bromine. I was hooked. Made many interesting and dangerous things, Chromyl Chloride, Iodine Monochloride, Sodium Tetrathionate - just stuff. But now I'm rambling off topic.

Aluminum foil, HCl in a tightly sealed bottle, unconventional (pressure) bomb goes boom.

[Edited on 31-3-2006 by JustMe]