querjek
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Alternatives to using a "pipe bomb" for a reaction?
I've seen referenced in literature a few times to use a "pipe bomb"--that is, a small, stainless-steel threaded pipe with caps and teflon tape
containing a reaction matrix. This is typically put into some sort of high-temperature device.
Maybe I don't understand the purpose of it completely, but--couldn't one use something like a flask submerged in a deep fryer or something of the sort
and avoid the "pipe bomb" all together?
it's all about chemistry.
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watson.fawkes
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Devices such as this are appropriate when internal pressures generated are greater than glass can withstand, or when the reaction temperature is too
high for glass.
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Nicodem
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| Quote: | Originally posted by querjek
I've seen referenced in literature a few times to use a "pipe bomb"--that is, a small, stainless-steel threaded pipe with caps and teflon tape
containing a reaction matrix. This is typically put into some sort of high-temperature device. |
I have doubts you saw the phrase "pipe bomb" mentioned in the literature. Using that term to search scientific literature only yields forensic papers
about pipe bombs of the exploding type. Can you show a paper where you have seen this phrase used?
The correct term for autogenous pressure resistant vessel is autoclave (in English as well). Alternatively, for pressures up to 20 bar glass closed
cap vessels can be used (there are several commercially available types).
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Sauron
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The term "bomb" does get applied to certain laboratory pressure vessels, for example calorimeter bombs. I have seen the term used more generally for
pressure reactors. For instance "reaction bomb".
This of course does not mean that the device is an explosive weapon, or anything of the sort. It is somewhat startling when you first encounter the
term.
Plumbing pipe of steel or stainless steel is usually cast and not very pressure resistant. The design and fabrication of pressure vessels is a
specialized engineering art and best left to the experts. References in the literature to reactions in sealed tubes be they glass or metal were
generally low pressure of autogenous origin.
Sic gorgeamus a los subjectatus nunc.
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chief
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In autoclaves usually the material is contained within an ampoule, close-sealed, possibly under high-vacuum. An glass-ampoule can withstand high
pressures, eg. a close-fused test-tube is gonna go up to 100 bar, and maybe much higher; the lower the diameter, the higher the pressure ...
Glass with 1mm strenghth, but only maybe 3 mm inner diameter, will withstand several hundered of bar.
Only: Sometimes these ampoules do fail ... and thats _one_ reason to contain them within an autoclave; another is to reach higher pressures, by
filling the autoclave partially with water, so within the autoclave will be some counter-pressure, relative to the inner of the ampoule ...
Definately such setups are regularly used in some sciences, to research hydrothermal crystallizations: Filling the ampoule with the reaction-stuff and
water to a precalculated %age will yield upon heating (several hundered centigrade, maybe well above the critical point of water) a known pressure.
Like that volcanic and geologic conditions are made in the lab ...
Also crystals may be grown that way, eg. quartz, but economically within large steel-tubes.
Anyhow: Such experimentation I would only touch with remote-controlling, in a distant bunker where it doesn't hurt, because who is gonna guarantee,
that after cooling down the ampule doesn't contain any residual pressure by some unforeseen reaction ... ???
[Edited on 12-11-2008 by chief]
[Edited on 12-11-2008 by chief]
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zed
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querjek,
Glass is generally not a suitable material for "Bombs". The experimental device that you have proposed, quite possibly might kill you.
Let's do a little thought experiment.....You want to run a reaction. for the reaction to take place, high temperatures are required. So, (as an
example) you fill a deep fryer (or a big pot) with two gallons of vegetable oil. Then, you place a 500ml glass flask in it, and you turn on the deep
fryer. The flask contains ethanol, water, and some reagents.....And for a little while, all seems well.
Unfortunately, as the temperature rises to the boiling point of your solvents, internal pressure in evolved. The higher the temperature goes the
higher the pressure goes
With a little luck, bad luck that is, that flask might actually withstand 10 atmospheres of internal pressure before it explodes. When it does
explode, there is a good chance it will blow Most of that boiling-hot vegetable oil right in your face. Along with broken glass and whatever is left
of your reaction mixture. Bad news.
If you must run a reaction that requires high temperature/pressure, and you do not have a suitable pressure vessel, a coil of small diameter stainless
steel tubing can sometimes be used as a reaction vessel. Small diameter tubing ( 1/4 in or less) can withstand very high pressures without rupturing.
http://www.webcoindustries.com/tubing/stainless/laserline/co...
[Edited on 20-11-2008 by zed]
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Sauron
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Commercial glass pressure reactors are rated for 40-60 psig, depending on capacity. Larger sizes = less pressure capability.
So we are talking 3-4 atmospheres only. See Parr's website for more information. Also Ace Glass, who make pressure reactors in glass. They really are
constrained to low pressure reactions and relatively low temperatures (obviously strength is inversely proportional to temperature, this is also true
of steel and other metals and alloys.)
Sic gorgeamus a los subjectatus nunc.
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kalacrow
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One safer home brew alternative is to use a tank designed for holding gases at high pressure, aka a small O2, N2, He2 or other tank (NOT H2 or
anything else. SCUBA tanks as well, but nothing that held gaseous reagents, H2 or hydrocarbons). The tanks are steel, so they might interfere with
your reaction, and unless you know steel will not interfere you shouldn't use them as is. They generally are rated at 2000PSI or greater. That's
usually high enough for any reaction, assuming you leave enough headroom in the tank. Also, acids could corrode the plug and cause it to pop during a
reaction.
If you have a few extra dollars, you can have a machine shop cut the bottom off, and make a screw fitting that screws on the bottom of the entire tank
which is rated at or above the pressure rating of the tank. That would be adequate for any pressure reaction that didn't require agitation.. you could
just put a flask inside the tank, secure it so it doesn't tip or fall, and heat the entire thing. You wouldn't have a way to measure temp inside the
tank, but the temp of the heating fluid would be a reasonably good approximation.
You can go farther and have the entire inside lined with glass. And have the shop add a pressure rated valve near the top of the apparatus so you can
drain your reaction mixture without removing the valve at the top and/or vent the pressure from a valve that is not the gas introduction valve, thus
lessening the need for worry about that seal.
At this point you have a tank that can even do hydrogenation, and if you know what you are doing you could use it in a roughly equivalent means as a
Parr shaker. Not as convenient, but probably not as expensive either.
In all of these cases, you would want to seal the valve entirely with teflon before the reaction, and also have swapped out the brass or steel gas
valve with stainless. Inspect the thing after and before every reaction to make sure it's not damaged, and inspect the threads in the apparatus as
well.
This is all second hand from folks whom I know have done this and have talked about it. I haven't done this myself, so do the research!!!!! If you are
at all worried about it, just save your money and get an autoclave and/or a parr shaker.
a pipe "bomb" is dangerous. The plumbing pipe found at hardware stores could be safely used for low pressure reactions, but anything that could run
away, you are risking explosion. Unless you know the pressure rating of a particular apparatus, and the maximum pressure that could be developed by a
reaction, its a gamble.
If you really want to do a reaction with a "bomb" type device, do the reaction surrounded by cinder blocks and have a shield between you and the
blocks. But if the reaction involves anything more hazardous than solvents, I wouldn't try it. The danger is too great.
[Edited on 24-11-2008 by kalacrow]
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MagicJigPipe
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| Quote: |
The term "bomb" does get applied to certain laboratory pressure vessels, for example calorimeter bombs. I have seen the term used more generally for
pressure reactors. For instance "reaction bomb". |
My guess would be that the term came about because of a pressure reactor's potential to become an "explosive device". Do you think so?
And also, I have seen "bomb" in the literature before. Give me a little bit and I'll find exactly where.
[Edited on 11-27-2008 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Nicodem
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The term "bomb" is a general term (not just in English but in many languages: http://www.etymonline.com/index.php?term=bomb ) and it is now widely applied also for pressurized gas vessels and as such it has certainly found
its way in the scientific literature. Yet, I don't remember seeing the phrase "pipe bomb" ever being used instead of "autoclave" in the literature. It
sounds as a really too dumb phrase to be used in scientific literature for something that already has a name.
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497
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I've seen "bomb" in some older literature, like on OrgSyn. Never "pipe bomb" though..
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Sauron
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"Reaction bomb"
Sample bomb"
"calorimeter bomb"
All commonly used for pressure containment vessels and none having anything to do with explosive devices.
Substitute "vessel" or "cylinder" as appropriate if the term makes you uneasy.
Or just take a tranquilizer.
Sic gorgeamus a los subjectatus nunc.
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