Hexavalent
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Cooling with Butane
I recently discovered that those mini butane refill cans have the liquid butane emptied out of them if done properly . . .how long would it last in a
Dewar (OK, a Thermos flask), and, if feasible, could you use it to cool samples as a substitue for an ice bath?
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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bahamuth
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It would last you exactly as long as to catch fire and show you how hell would look like if it existed...
Cooling mixtures are a much smoother way to go and are already discussed here alot amongst here: Endothermic freezing mixtures
Any sufficiently advanced technology is indistinguishable from magic.
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DJF90
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Butane has a bp of -0.5*C and a specific heat capacity a lot less than water does (as do many things..). It would not last even 1/10th of the time of
an ice bath, which conveniently can be made colder than 0*C by the addition of any of several salts to exploit freezing point depression and
endothermic dissolution. I've personally liquified a small amount of butane in a test tube using a salt-ice bath, and it was cool to see the liquid
boil so vigorously when removed. All was done with no sources of ignition within the vicinity, of course.
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Hexavalent
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Thanks for the ideas everybody, as aforementioned it was only an idea that I wanted to check out with the more experienced chemists.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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Bot0nist
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Meth cooks use this method to condense ammonia as it is liberated from it's salts, IIRC. Sounds like a really dangerous way to achieve those
temperatures. I'm a fan of dry ice and acetone myself, though salt/ice baths are plenty cold for many needs.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Mailinmypocket
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I've used it before to try cooling things... Last time was to fill a vial with it and freeze a smaller vial within it, it was a bit of a pain to
handle with the spraying from the can (I used a fork and wedged the little tip between the prongs to press the red nozzle down, if you are talking
about lighter refill cans) anyways... the flammability issue constantly nagged at me, dry ice is way better IMO, you might suffocate if you use it in
small enclosed areas but it won't blow you up if you plug something in or flick a switch!
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peach
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| Quote: | | could you use it to cool samples as a substitue for an ice bath? |
You could, but I'm not sure why you'd want to, with it boiling off at -1 and producing a serious fire hazard.
Make or buy a bag of ice cubes. Wrap them in a towel, smash them to dust. Stir in some table salt and it'll reach -20C, minus the butane cans and
fires.
Quote: Originally posted by Bot0nist  | | Meth cooks use this method to condense ammonia as it is liberated from it's salts, IIRC. Sounds like a really dangerous way to achieve those
temperatures. |
It'd have to be under vacuum, since anhydrous ammonia boils around -33C and the butane at -1C. A lot of the home brew CPU coolers use butane as the
refrigerant (and will reach about -30 to -50?C from memory, with one stage; some of the overclocker guys have managed -90 to -100 with a single stage,
again from memory). The tens of cans of engine starter and lighter fluid you'll commonly see in photos of meth labs are more often being used as
solvents.
Rather than trying to condense the ammonia at atmospheric pressure, there is a process that involves generating it in situ, alongside the lithium, in
a plastic bottle with the cap screwed on. I think the vapour pressure of ammonia at room temperature is about 150psi. The lithium can end up burning
in the bottle, melting it's way out the side. The ammonia is flammable, so things 'warm up' when it escapes in the presence of burning metal. Combined
with cans of emptied starter and lighter fluid hanging around, there's going to be a fire.
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Bot0nist
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I think that is the infamous "Shake n Bake" 
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Hexavalent
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Thanks everybody . . peach and DJF90, have you ever tried to locate dry ice in the UK at all . . .it would be nice for some physical chemistry
experiments as long as its not confined . . .
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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peach
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Heston Blumenthal was going on about it in his program 'How to cook like Heston', regarding the making of bacon and egg ice cream. He mentioned it
being easy to buy blocks of online. It is easy. However, it is not cheap.*
A lot of places sell solid CO2 to catering, medical and theatre people, who want multiple kilos of it per box, and use it up quickly. For a few
chemistry experiments now and again at home, you'd end up buying far more than you need, paying a lot of postage and the rest of it would then
sublimate off before being used; money literally out the window.
If you're using it at home, rent a CO2 cylinder with a siphon tube and squirt the liquid CO2 into a bag to form it yourself, on demand. As with
everything in the UK of late, the costs can be tedious. As far as I'm aware, BOC, Air Liquide and Air Gas don't refill privately owned cylinders.
*I don't consider a bowl of ice cream with £30+ worth of CO2 used in it's preparation, cheap. Neither do I see the point in squirting multiple cans
of air duster onto a surface to cool it to -20C, when it is flammable, not food safe, expensive and a normal domestic freezer will reach -30C. Just
put the chopping board in the freezer!
[Edited on 12-4-2012 by peach]
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DJF90
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Dry ice is available and as peach says it is expensive. If you're going to shell out for it, get it as a block and not as pellets as the smaller
surface area will help keep it longer. We store ours in the lab in a polystyrene box (similar to those that vaccines are delivered to a medical center
in, and it'll keep 8-10mm pellets overnight with a small loss.) We normally go through about 5kg a day, filling three dry ice traps for the buchis,
while the highvac lines are trapped with LN2. Dry ice is easy to break up, but bear safety in mind when adding it to acetone in a dewar... a SMALL
amount first, then gradually add more. I've seen someone dump a whole scoop in at once and the resulting volcano was pretty impressive. However,
despite its academic and industrial versatility, you wont see me ordering any since unless you're a hardcore organic chemist at home, you wont really
need it. Even lithiations can be done with a salt ice bath (I've seen some at room temperature!) - the only real downfall of not having dry ice is
things like DIBAL reductions of esters to aldehydes where the tetrahedral intermedate falls apart allowing the reduction of the desired aldehyde. This
can be circumvented using Weinreb amides and LiAlH4 but you wont see these at home commonly...
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Hexavalent
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I see, thanks for your help. I actually wanted mine for stuff just like that and experimentation with concepts such as Charles' Law regarding the
volume/temperature relationship of gasses. It would also be nice for doing some demos and testing air velocities with different fume hood sash
positions. etc. . .I believe the Americans can often get it at supermarkets/grocery stores, which would be nice here but sadly unlikely to happen . .
.I wonder if it could be produced using the method that peach desribed with the CO2 cylinder but with a fire extinguisher . . .
[Edited on 12-4-2012 by Hexavalent]
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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bfesser
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It can be produced with a CO<sub>2</sub> fire extinguisher, but it's incredibly inefficient, expensive, and wasteful.
I've liquefied butane before by compressing it inside a glass syringe. I don't recommend this, though, as you'll likely break your syringe!
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peach
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A 2kg CO2 extinguisher from ToolStation.com (the cheapest UK general tool supplier I'm aware of) is £65.33*. You'll get, at most, 1kg of dry ice from
that. Making it some expensive stuff indeed. On the brightside, free delivery and a handy plant pot once the extinguisher is flat. My neighbour has
one he charges up with a foot pump to shoot the local kitties with water.
6.5kg beer cellar CO2 cylinder fill is about 23 squids.
*Never, ever, steal, borrow, move or mess with fire extinguishers or any other life saving equipment, no matter who's it is or where it is. It is a
defining line between being a bit of an idiot and being responsible for someone dying. The people depending on it being there will not have time to go
out and buy another when they discover it's missing and someone is on fire, no matter how much money they have. It takes seconds to receive 3rd degree
burns, and only a few more for it to become fatal. Subjecting anyone to that is, without question, as low as it can go. I have had to put my own
brother out with one. The screaming was the most disgusting sound I've ever heard. It is not as it is on TV, it's impossible to create that sound on
demand. It is a unique sound I will remember for the rest of my life.
[Edited on 12-4-2012 by peach]
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annaandherdad
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I've liquified SO2 in the past using salt-and-ice to cool the gas. This is at atmospheric pressure, I mean, bp is -10 C. I didn't measure the
temperature of the salt-ice mixture, but it must have been less than the bp.
And yes, dry ice is expensive around here (California).
Any other SF Bay chemists?
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Hexavalent
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I like that idea, annaandherdad (regarding the SO2), I've also seen a sample of liquid NOx prepared on YouTube somewhere in a similar fashion.
As for the butane, I've given up on the idea. I'm looking into the various salts ATM and trying to find one that's practical to me regarding chemical
availability versus temperature achievable.
The dry ice situation is the same here in the UK - widely available, but certainly not cheap
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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