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mr.crow
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Alternative inert gasses
I had a weird idea today, thinking about how to get some sort of inert gas.
1,1-Difluoroethane is available in canned air dusters and looks pretty non reactive. However they include a bitterant to stop glue sniffers from
inhaling it. This must be an aerosol that can be filtered out or absorbed.
Butane is also easy to get and use from lighter refill cans. It has a slight odor but not like the sulfides they put in natural gas. The downside is
its flammable but at least its chemically inert. Squirt some into your flask to displace all the oxygen.
You can also build a home made liquified gas cylinder. Get some galvanized iron pipes from home depot, an end cap and a ball valve. Fill it up with
your cryogenic liquid and then close the valve. Bingo! Attach a needle valve and hose barb to the top for flow regulation. The pipes would easily
withstand the pressure of these substances.
What do you think of these ideas?
Double, double toil and trouble; Fire burn, and caldron bubble
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paulr1234
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Helium can be purchased in those party cans for balloons, expensive compared with dry nitrogen but easy to obtain and those pink cylinders have a
built-in regulator (of sorts). Given that it is lighter than air, I would use purge the system especially well. Not sure how dry or pure this source
is however, plenty inert tho.
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AndersHoveland
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Many of the helium tanks sold at party stores also contain 10-15% oxygen added, to reduce the danger of suffocation if the gas leaks, or when people
inhale the helium from balloons.
One good inert gas for most applications is carbon dioxide. It can either be produced by reacting sodium bicarbonate (baking powder) with sodium
bisulfate, from the sublimation of a piece of "dry ice" (sold at some supermarkets), or from compressed gas cylinders (one source might possibly be
those used for toy guns).
Welding stores can rent tanks of argon (usually expensive). Nitrogen would also be an good gas, but I know not where one could buy compressed nitrogen
tanks.
[Edited on 24-12-2011 by AndersHoveland]
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Neil
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Quote: Originally posted by mr.crow  |
You can also build a home made liquified gas cylinder. Get some galvanized iron pipes from home depot, an end cap and a ball valve. Fill it up with
your cryogenic liquid and then close the valve. Bingo! Attach a needle valve and hose barb to the top for flow regulation. The pipes would easily
withstand the pressure of these substances.
What do you think of these ideas? |
That's a pipe bomb, no way a pipe is going to keep N2 liquid without blowing up. Even CO2 would be pushing the pressure limits on schedule 40 - or did
you mean something like R22?
The canned air dusters make sense. You can also buy cylinders of liquid CO2 from brewing stores, welding stores etc.
Some tool/paint/marine shops sell a mixture of inert gasses which are intended to be used in flushing the air out of epoxy cans.
http://www.leevalley.com/en/wood/page.aspx?p=30268&cat=1...
In the past you could get the cans of dusting gas that were Tetrafluoroethane IIRC - non flammable. Not sure if you still can and not certain if it
was Tetrafluoroethane but I do remember that you could get ones that were flammable and ones that were not. You can get refrigerants for re-filling a
AC unit from most hardware/car stores.
[Edited on 24-12-2011 by Neil]
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Neil
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| Quote: Originally posted by AndersHoveland | | Many of the helium tanks sold at party stores also contain 10-15% oxygen added, to reduce the danger of suffocation if the gas leaks, or when people
inhale the helium from balloons. |
Not true, check the MSDS sheets for them; the impurity tends to be N2.
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AndersHoveland
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It really depends on what region of the world you are in, and even then there is much variation between different suppliers.
[Edited on 24-12-2011 by AndersHoveland]
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Neil
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Possibly, I tried to find any that had O2 in them in the past but could find none. The O2 thing seems to be an urban legend, or at least something
that was phased out?
All the helium comes from the same place so for one brand to contain O2 it would have to be added by whoever was re-selling it. Anyways, Darwin is
much better at watching out for fools.
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mr.crow
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| Quote: Originally posted by Neil |
That's a pipe bomb, no way a pipe is going to keep N2 liquid without blowing up. Even CO2 would be pushing the pressure limits on schedule 40 - or did
you mean something like R22?
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You are right, I meant only for Difluoroethane and Butane. Don't put LN2 or dry ice in it!!!
CO2 is also good but watch out for it reacting with things like grignards or NaOH. I have a refillable CO2 tank for inflating tires but I don't know
where I can get it refilled
Helium is not good, is lighter than air and has oxygen or other gasses in it.
What got me thinking is these little cheesy spray cans for flushing the air out of wine bottles. Its just a slightly compressed gas so its a total rip
off. Just drink the wine or get some friends to help!
Double, double toil and trouble; Fire burn, and caldron bubble
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Vogelzang
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After paying over $100 for the nitrogen tank on the left in the picture, it only costs about $11 to refill it. The price might have gone up, though.
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Neil
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Ahh! I thought it weird that you seemed to suggest something like that.
For filling a CO2 canister check out local beer brewing shops, welding shops, or find your local Prax/Air Liquid or whoever sells gas in your area.
Every bar goes through a couple bottles of CO2 for their kegs and fast food places for their soda - it is there you just need to dig a bit 
Alternatively check your phone book for paint ball places - sometimes the do bulk fills.
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Lambda-Eyde
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1,1-difluoroethane and the other haloethanes are likely to dissolve in organic solvents which may or may not be a drawback. Carbon dioxide, as already
mentioned, isn't really that inert and reacts with bases and grignard reagents among other things. Dicking around with butane is borderline suicidal
if you ask me (and also smells like shit and will screw with your brain if you breathe large amounts of it), I don't see why you can't go to the
nearest welding store that stocks argon cylinders. I can buy one liter of Ar for ~20 €, which is very much worth it.
This just in: 95,5 % of the world population lives outside the USA
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paulr1234
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If you do buy a big cylinder of N2, make sure you secure it properly; knock it over with the regulator in place, and you risk having the thing flying
around like a guided missile.
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BromicAcid
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| Quote: | | If you do buy a big cylinder of N2, make sure you secure it properly; knock it over with the regulator in place, and you risk having the thing flying
around like a guided missile. |
Don't you mean misguided missile?
[rimshot] [/rimshot]
Really though, there is also a thread around here on using the nitrogen in the air for inerting purposes. It was in an older inorganic syn book and
the main component was hot copper wool as a scrubber for the oxygen to make something that was useful for Schlenk line use.
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peach
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My first contact with the net, back before my teens, when the three users were all on dialup and when it took an evening to download one photo of a
naked girl, was with welding, casting and laser email groups. The guys from the US would frequently mention buying the cylinders as opposed to renting
them. That is something which seems much easier in the US than the UK. If you can buy one and have it refilled, definitely go with that option.
The original inert work, before cylinder gases were as commonly available as they are now, was done under hydrogen. 
We're a long way on from there now. The guys over at extreme overclockers (who are well used to working with gases) actually banned entries to one of
their competitions if they included propane as one of the refrigerants, due to the risk of the entrants exploding.
Rent or buy one of these:
Or, buy one of these disposables:
I really don't think it's worth messing around with the inert stuff. It is hard and dangerous enough as it is without using air dusters or propane
tanks. At best, it is painful to watch something degrade after putting in days worth of loving effort, simply due to trying to go cheapo on the gas.
For example, how dost thou intend to make an air tight, regulated seal between said air duster and the glass? LN2 in a DIY cylinder is not a good idea
at all. If that goes wrong, which it likely will, it'll go with such an immense bang you may not even remember it.
Renting the cylinders for at home chemistry is generally too expensive. In the UK anyway. The rental is far too much versus the usage rate. You want
to buy one and pay for the refills if you're not also using it for welding (which will rape the gas by comparison).
The smallest inert cylinders from British Oxygen are X sizes I think (waist height). The rental is about £70 a year and a single fill will last about
a year, making the rental alone double the cost of the gas. I took my last one back with most of the cylinder still full, after a year.
The disposables in the second photo are £10.50 each. The gas is at a premium per unit, but the lack of rental charge makes them very appealing; I
would need to buy seven of these things to offset the rental alone on a commercial cylinder, and three to five more to offset one fill.
Welding argon and nitrogen is used by universities. They don't use specialty grades for regular inert work; because they cost an absolute fortune and
there's no need.
As I'm already on the beers for Christmas, now might be the time to wish the fiery ship science madness a merry morrow.
[Edited on 25-12-2011 by peach]
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mr.crow
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Yay for Christmas beer 
The disposable argon cylinders look like the best bet. Everyone should find a way to get one. I'm unwilling to rent or buy a real cylinder
To get a proper connection to the apparatus I would transfer the liquified gas to the home made pipe cylinder.
Good point about dissolving in organic solvents. At reflux this shouldn't be a problem. How about difluoroethane reacting with NaOH?
Butane sounds really dumb but the risks don't seem that bad compared to diethyl ether. Only do this outside of course
Double, double toil and trouble; Fire burn, and caldron bubble
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barley81
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How about plain old propane? I unscrew my propane torch's 'flame stabilizer' thingy and stick clear vinyl tubing on it to supply my Bunsen burner.
Even if it contains some smelly sulfur compound, it's only a trace and shouldn't interfere with most reactions. Of course, it is a good idea to use it
as inert gas outside, and far away from sparks or flame.
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peach
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<iframe sandbox width="640" height="480" src="http://www.youtube.com/embed/lITBGjNEp08" frameborder="0" allowfullscreen></iframe>
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barley81
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ROFL
Seriously though, if butane can be used in some cases, then why not propane? It's much cheaper and seems like it would do all right for a few (safe!)
things.
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peach
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| Quote: Originally posted by AndersHoveland |
Welding stores can rent tanks of argon (usually expensive). Nitrogen would also be an good gas, but I know not where one could buy compressed nitrogen
tanks. |
Same place.
The welding yards also sell OFN (oxygen free nitrogen) for pubs and pressure testing.
| Quote: Originally posted by barley81 | ROFL
Seriously though, if butane can be used in some cases, then why not propane? It's much cheaper and seems like it would do all right for a few (safe!)
things. |
It's certainly possible.
The question is, why would you want to use a gas that is so much more prone to fire, explosions and side reactions. And it really is so even given the
extra cost of argon.
Star Trek analogy on route: It's like cleaning a toilet with a reach around when there's a plunger right there beside you.
Speaking of which, all this air duster talk reminds me...
<iframe sandbox width="640" height="480" src="http://www.youtube.com/embed/C1zzJIWKCMw" frameborder="0" allowfullscreen></iframe>
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White Yeti
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What's wrong with CO2? It's cheap, readily available, inert and denser than air (thus displaces it quite well).
"Ja, Kalzium, das ist alles!" -Otto Loewi
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Lambda-Eyde
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As previously mentioned, carbon dioxide is in fact an acid. It will dissolve in water, react with hydroxides and turn your grignard reagents into
carboxylic acids. And it's not that much cheaper than a 1L disposable argon cylinder (Ar will also displace air). But yes, sometimes carbon dioxide
will be more than adequate, but it will also interfere with a number of reactions. If you don't have 100 % control (which few of us have all the time)
you'll probably have the same problem like this guy one day.
This just in: 95,5 % of the world population lives outside the USA
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White Yeti
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| Quote: Originally posted by Lambda-Eyde | | As previously mentioned, carbon dioxide is in fact an acid. It will dissolve in water, react with hydroxides and turn your grignard reagents into
carboxylic acids. And it's not that much cheaper than a 1L disposable argon cylinder (Ar will also displace air). But yes, sometimes carbon dioxide
will be more than adequate, but it will also interfere with a number of reactions. If you don't have 100 % control (which few of us have all the time)
you'll probably have the same problem like this guy one day. |
Right, but for many other, more forgiving reactions, CO2 works just fine. If all else fails, a trip to the local balloon shop will get you a
completely inert gas (as previously mentioned). If I were trying out a grignard reaction, I wouldn't be stupid enough to loose sight of the big
picture, and to realise that an inert atmosphere should be the least of my worries.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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plante1999
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With out catalyst hydrogen is an somewath inert gas...
I never asked for this.
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Mr. Wizard
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Propane and it's higher boiling relative butane can be used to cover some reactions where oxygen would be a problem. Remember that propane and butane
are NOT pure when sold for fuel purposes. I always assumed they were, but they are just a combination of gasses that will distill over at a certain
pressure and temperature. Propane especially can contain various alkenes and alkynes. I used to use a lot of it, and burned it as motor fuel, and was
familiar with it's sale and handling. As time went by I realized it was not a pure substance. In warm weather it was sold with more of an admix of
butane to lower it's vapor pressure , to prevent tank venting. Butane is also added to low octane gasoline to boost it's octane rating. This might
work well in cooler climates, and where the gasoline is consumed quickly, and be problematic in warmer climates.
Alkenes, and alkynes accidentally added to many reactions could lead to big problems. Be careful using LPG (Liquified Petroleum Gas) as an 'inert'
gas. That said, it can be used to flush oxygen out of containers. Perhaps you could test your gas with a permanganate solution or a bromine solution
before using it in a critical application. The price is certainly better than argon or compressed N2.
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MagicJigPipe
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"Many of the helium tanks sold at party stores also contain 10-15% oxygen added, to reduce the danger of suffocation if the gas leaks, or when people
inhale the helium from balloons.
One good inert gas for most applications is carbon dioxide. It can either be produced by reacting sodium bicarbonate (baking powder) with sodium
bisulfate, from the sublimation of a piece of "dry ice" (sold at some supermarkets), or from compressed gas cylinders (one source might possibly be
those used for toy guns).
Welding stores can rent tanks of argon (usually expensive). "
Niel is correct about the 20% oxygen thing being an urban legend I think. I have talked to several He tank suppliers and none of them had any idea
about it. In fact, one, "Party Time", claimed that their He was 99.99% (possibly one more nine, I can't remember exactly) "pure". I understand that
companies have a dubious history of claiming things to be "100%" pure and things of that nature, but I tended to believe them as if he was just
reading a label from the huge tank that they fill the small ones from.
Also, 1,1,1,2-tetrafluoroethane is still INSANELY available. It's everywhere. Everywhere you turn SOMETHING has TFE in it. Not to mention it is a
common refrigerant (can't remember the "R" number; 134a?).
And I don't consider argon very expensive unless you're comparing it to CO2 or maybe N2. You can buy 20 ft^3 (I assume that's at STP) for about $10.
I am constantly surprised at how much that is.
And remember, all this applies to the US only. I can't vouch for anywhere else.
[Edited on 12-26-2011 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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