one for the chemists

I saw a show on the history channel about the Texas City disaster where a ship loaded with ammonium nitrate caught fire and eventually
blew up. Some people at the time had thought that this fire would have just continued to burn without any explosion. This got me to thinking about all the explosive compounds that have been discovered over time. Undoubtably many people have been killed or injured by their latest discovery. On a visit to the Air & Flight Museum in Seattle my brother and I took a tour of a Blackbird. The one at Boeing is not an SR71. It predates that model. But it's still the same basic plane, goes as fast, and uses the same engines. A fuel was developed for these planes that is very hard to ignite. This special fuel was used to cool the plane before it was burned (the fuel, that is), did not vaporize easily, and in fact would not ignite even when squirted into the superheated air inside the engines when the plane was at speed. The compression ratio inside the engine near top speed is 40 to 1 so you can imagine how hot that air was. A chemical was used to ignite the fuel. It combusted almost explosively whenever exposed to air. Each engine was equipped with a 16 oz. cannister of this stuff and a 1 oz. shot was used each time the engine ignited and each time the afterburners were lit off. I wonder if this nasty stuff was designed or found by accident? Do modern chemists have a pretty good idea what a theoretical compound will do? Can we tell if something is going to be stable before mixing it up? Just curious. It seems to me that with physics and chemistry so intertwined that we should have a pretty good idea what something should behave like before we make it. Not only that though. We should be able to look at a need and have some idea what kind of compound we need to fill that need. So just how well can we predict these things today? Thanks, Eric
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There are two issues regarding explosives: 1. the relative energy difference between the starting and final chemical products; 2. How fast these changes occur, ie, the kinetics of the reaction.
(1) tells us if an explosion can happen at all-- the "delta H" of the reaction *must* be negative, ie, exothermic, for an explosion to take place. This can be predicted w/ great accuracy, from well-tabulated fundamental data. But, (1) is not sufficient.
If (1) says an explosion *can* occur, (2) will tell you if it *will* occur, ie, does the energy change occur *quickly enough* to "rate" as an explosion. (2), however, is the variable that is not so easy to predict. An experienced explosion guy will have a good idea, but will never be able to say for sure. For example, picric acid is fine in solution, or moist. When solidified, such as dried film in a flask, it is truly explosive. They only found that out the hard way. Ditto nitro/TNT, other stuff.
A really good explosive material will have a very large delta H, occuring very quickly. Anything else compromises the explosive value.
Interestingly, these very same concepts are at work at body temperature in enzyme systems in human metabolism. Short of explosions, of course... well, depending on what you ate.... :) -- Mr. P.V.'d formerly Droll Troll

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wrote:

No-one (still) understands the explosive behaviour of AN. It _shouldn't_ do what it clearly does on rare occasions. We only believe that it can explode because all the unbelievers are now dead, killed by exploding AN.
Just look at the hole an AN explosion made in the BASF plant at Ludwigshafen.
Remember Charles "Bermuda Triangle" Berlitz? His disappearing "innocent little freighter with a cargo of mere fertiliser" was carrying AN (which of course he never mentioned). I think we can guess what happened there....

It's an A-12, the first of the three blackbird models. Actually that one's an M-21, the version built to carry the D-21 drone, but it's close enough.

Triethyl Borane. Burns with a green flame too
It's not _that_ bad. It's less irritable that AVPIN (isopropyl nitrate) used as a monopropellant in some jet engine turbine starters. Even the _exhaust_ from those is highly flammable!

It's got boron in it, so whatever it does, it will do it energetically. Search for "boron" "zip fuel" and the "B70" bomber program.
Yes, chemists do everything on blasted screens these days, instead of cowering behind them for safety. If you're a super-annuated chemist from back in the days when chemists were _real_ lab chemists, chances are that you're now unemployed or shovelling shit doing chemwaste cleanup as a peon.
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Triethyl Borane is also pyrophoric which means it spontaneously catches fire on contact with air (it will even catch fire on contact with dry N2 which says something). Borane compounds are definitely not something you want to be around. Old boron chemists all have a Parkinson like palsy that is caused by the boron they've breathed screwing up their motor neurons. I'm not surprised it would kick start a Blackbird engine. Two puffs of it would probably blow the engine off the wing.
Most old time explosives like TNT and Nitroglycerine were found by chance but these days chemists have a pretty good handle on what is needed to cause an explosion (like an internal oxidizer on the same molecule as the fuel) and have developed whole families of explosives / solid rocket fuels (same stuff, just a rocket has a vent on it) with very tightly controlled characteristics.
There are still surprises, though. I've heard that Triacetone Triperoxide (TATP), beloved of terrorists because it's high energy, easy to make and hard to detect, was originally discovered by a guy that was working on developing industrial epoxies. Glad I wasn't in the lab when they tested that.
By the way, I think Ammonium Nitrate (NH4NO2) explosions are pretty well understood these days. I don't remember the details, but it has to do with the temperature and pressure getting high enough that the NO2 starts to break down, releasing O2 which reacts with the NH4.
Jim
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Jim McGill wrote:

My understanding is that gun cotton was discovered before nitroglycerine. It was not known if gun cotton was modified cotton or if the cotton was adsorbing and holding the explosive. Someone recommended an experiment using glycerine in place of the cotton. The two being similar, but of course the glycerine has no adsorbing power.
Dan
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Great reply, Dan!
I've always wondered, "Why glycerine"; and what specific properties does glycerine have that makes it the best choice for nitration to this day? I understand most anything can be nitrated but I often wonder why we still use glycerine. It was readily availble in the 1860's; but I wonder if some synthetic is available now that woud be as good, or better, than glycerine for use in dynamite manufacture.
Bob Swinney

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On Fri, 27 Jan 2006 13:23:16 -0600, "Robert Swinney"

It's tri-functional and cheaper than dirt. Now that bio-diesel's big, there's a glut of glycerine, a huge by-product. Dow just announced closure of synthetic glycerine production except one plant in Europe.
There's probably a lot of chemists trying to find more uses for the stuff right now.
Pete Keillor

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There's a book on nittroglycerine, history and manufacture circa 1920's, that I've got. Lots of other nitro esters have been developed, none with the particular properties that nitroglycerine has and none so cheap. Glycerine is/was basically a waste product from soap manufacture, so was dirt cheap when dynamite manufacture began. Once demand got to the point where it outstripped that source, synthetic methods took over for glycerine production. As far as commercial explosives are concerned, dynamite use has declined since the advent of ANFO and slurries. They're much easier to handle in quarries, cheaper and safer to store. History Channel just ran a rerun of their Modern Marvels on dynamite, it touched on a few of those points.
As far as special properties, stability is one big plus(samples have stayed stable for many years at room temperature), it doesn't evaporate like a lot of other nitro esters, is relatively inert with regard to reacting with metals and other substances and is relatively insensitive compared with other compounds. Plus it's a lot cheaper to make than a lot of other compounds. Also powerful for the amount of explosive involved. Manufacture is fairly straightforward but not something you set up in a populated area.
Stan
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"but it has to do

Yeah, sort of an abrupt dissassociation; and that free O2 reacts with everything around it.
Bob Swinney.

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Eric R Snow wrote:

Well, back in the middle ages, a lot of alchemists died in explosions accompanied by fireballs and a strong odor of brimstone.
Demons, obviously.

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In the late 1800 and early 1900's a lot of really good Physicists and Chemists died due to carelessness or lack of knowledge at the time.
The Leyden jar killed more people than it should - and created a depression of research. The great Chemists - discovering radiation - Curie - died from their ignorance of radiation.
Dangers exist. Science and Engineering isn't an office job.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder
Tove Momerathsson wrote:

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What did Ben Franklin say when he grabbed that key, during his "discovery" of electricity? Gaaawwwdamn!
Bob Swinney

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Yep -- Humphry Davy died inhaling oxides of nitrogen. Turned out they weren't all as much fun as nitrous oxide.
Even the technique we learned in high school, of wafting vapors toward the nose with the hand, is considered incredibly stupid these days.
Martin H. Eastburn wrote:

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On Thu, 26 Jan 2006 22:38:18 -0600, "Martin H. Eastburn"

It still happens these days. Karen Wetterhahn died from dimethyl mercury poisoning (this came up recently in the group, actually) due to the researchers at Dartmouth not performing tests to find out whether their gloves were any use at all. A rather sad death since it wasn't due to a bad lab accident or failure to follow proper procedure. Proper procedure was simply inadequate.
http://en.wikipedia.org/wiki/Karen_Wetterhahn
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Like a number of scientists and engineers that died from exposure while making the two WWII A bombs. So little was known in the new science of nuclear that even the experts were careless. Some mistakes made and some were to save others.
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder
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Being a chemist is actually still a pretty dangerous occupation. The American Chemical Society publishes stats once a year and it's a rare year when only one chemist or grad student is killed. Often it's people doing research that stumble onto some new toxin or some nasty side reaction that goes "BOOM". Not a terribly big field, so the actuarial statistics are pretty ugly.
Just after I got my degree from U.W., Seattle, a grad student I knew was killed by a major explosion that burned up most of the undergrad organic lab. It was a series of errors, no one of which would have been bad, but together were deadly. Poor guy was standing right by the hood when it went and got a lung full of NO2, which instantly became nitric acid and dissolved his lungs. Probably dead before he hit the floor but a nasty way to go.
Mac (happy to be out of the lab and programing computers now)
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Unfortunately, I've had some exposure to victims of inhalation of caustic substances.
It's _never_ "dead before he hit the floor". Rather, it's an excruciatingly painful, slow death as the person - writhing in pain - slowly drowns in his/her own body fluids and vomitus.
LLoyd
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I knew two lady chem teachers that moved away from chemical plants after loosing a husband. They had worked in the plant, different lab.
Physics is not as dangerous, but when it gets going - it can be deadly. Engineering can be dangerous - ever go into a blasted out tunnel ? and have it fall in ?
Real life is often tougher than the banker or shoe salesperson thinks. The rascals are the insurance people - they keep the numbers and always charge more.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder
Jim McGill wrote:

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