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Magpie
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argon
I have never used an inert gas but have been thinking of buying the equipment necessary for providing argon. Seeing that Klute was using a lecture
bottle for his argon made me think that a thread for discussing options and costs might prove useful.
In the US the gas cylinder capacities are rated in cubic feet (1CF = 28 liters), at room temperature and pressure. So common sizes are 20, 40, and 80
CF. These are basically designed to serve the welding industry. You can rent cylinders, but it seems that you could pay for owning your own fairly
quickly, depending, of course, on usage.
I'm thinking of buying a 20CF cylinder for ~$75 from my gas supplier, which includes the first fill of Ar. Subsequent fills are $20 each. Filled
pressure is ~2300 psig.
A nice 2 guage, single stage regulator, with output valve and output guage range of 0-60 psig can be had from micromatic.com for $46.
What are your experiences/preferences/thoughts?
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MagicJigPipe
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I've often pondered the same thing. I was wondering (since I just recently purchased 4 Medical E Oxygen cylinders) if it is possible to convert a
cylinder in some way (within regulations) to be used with a different gas as long as the construction material and operating pressure rating are
sufficient.
560 cubic feet sounds like a lot. I'm trying to picture in my head how large that is.
I'd say go for it. At 70 bucks to OWN a filled tank and only 20 bucks per fill after that. Sounds like a pretty good deal to me.
Are there any reactions you plan on doing soon that would benefit from an inert atmosphere?
"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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tumadre
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As long as the gas is inert, there should be no problem with filling it with a different gas.
I believe the regulation[s] are that a tank be hydrostatically tested or eddy current tested if it's aluminum every 5 years, and inspected every year.
MagicJigPipe, a 20 CF tank is 560 Liters @STP or .56 cubic meters
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Magpie
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MJP asks:
| Quote: |
Oxygen cylinders) if it is possible to convert a cylinder in some way (within regulations) to be used with a different gas as long as the construction
material and operating pressure rating are sufficient.
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From a structural standpoint I do not see why not. The rated pressure, I find, is stamped on the top of the cylinder, as a suffix of a longer number.
Like for the argon and N2 tanks it is usually 2015 psig. Then the gas supplier will fill it to ~2300 psig as a certain percentage over-pressure is
allowed.
Your problem is going to be the cylinder valve. For inert gases (N2, Ar, and I believe He) this is CGA-580. I'm pretty sure this valve is different
for O2. Might even be threaded different "hand." But I don't see why that valve couldn't be changed to a CGA-580. The regulators for N2 and Ar are
also designated CGA-580, male end.
Edit: And the gas supplier is going to be looking for a CGA-580 valve to fill with Ar or N2.
[Edited on 16-4-2008 by Magpie]
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vulture
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Oxygen tanks require grease free valves, that's why they're different. Just like you don't want any copper valves with acetylene.
BTW, make sure you have a spot to properly secure the tank. You don't want it falling over and the valve breaking off. Also mind that Ar is heavier
than air which may become a problem in a confined basement.
I know this sounds overzealous, but safety precautions are not overrated when working with high pressure gas containers, contrary to some inflated
regulations concerning chemicals.
[Edited on 16-4-2008 by vulture]
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Klute
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I started off using disposible cartridges because i didn't use inert gas very often, and most of time i only used a blanket, not a stream. But those
disposible bottle can come in expensive (12E), once one emptied itself because of the valve got damadged. I had to change both. I'm pretty sure 'ive
spent more than the price of the rechargeable 500L bottles (57E+ 22E regulating valves, but 6E for a recharge). They do sell 100L bottles, but they
don't have the regulator to go with it! I couldn't find any elsewhere, except in those MIG soldering station units.
I'm waiting to be in a more confortable economic situation to buy it, and i will need to do a little work to attache the bottle and get a good
system.
Having recently been given a vacuum distribution ramp (10 taps, with a vacuum "bubble" to keep them in place), I'm thinking of building a
do-it-yourself inert/vacuum manifold.
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MagicJigPipe
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I know I will most definitely need to change the valve. It's very strange. Something I have never seen before as I've never worked around medical E
O2 cylinders.
Here's a picture. The tank is steel and VERY heavy for it's size. I would weigh it but my large scale isn't working. If I were going to guess I
would say it's about 35lbs (16kg) empty. This one is the most rusted out of all of them.
[Edited on 4-16-2008 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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Magpie
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MJP: That cylinder looks quite tall - 5' or so. I'm guessing that it is at least 80 CF capacity. I'm also guessing that you can replace that valve
with a brass CGA-580 valve so you can get the cylinder filled with inert gas. The tank I'm considering is also made of steel.
BTW it doesn't cost hardly any more to fill an 80CF than a 20CF cylinder. It's the labor that you pay for - at least in my locality.
[Edited on 16-4-2008 by Magpie]
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MagicJigPipe
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Sorry, I forgot to put it in perspective. It's a little over 2 feet (61cm) tall.
Thanks for the advice. I'm excited now. And I have 4 of them!
"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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Magpie
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I now have argon on demand.  I purchased a 40 cubic foot cylinder and a
pressure regulator. So now I am set up for some syntheses heretofore out of reach.
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Picric-A
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very nice magpie! distillation of sodium is around the corner 
i am probably going to buy a small disposable tank of Argon like Klute, i guess it will be extremly usefull,
i need to find out how i flush out jointed distillation apparatus with it though... any help?
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Magpie
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Well Picric, I have no experience yet, but my first planned use is that very thing. I will be flushing an equipment train of hot flammable gases at
shutdown. I plan to just set the outlet pressure very low, say 5-10 psi, then just crack open the red ball valve on the regulator to allow a gentle
stream of argon to flow through the equipment for a minute or so. Perhaps others with experience can give better advice.
[Edited on 26-8-2008 by Magpie]
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Klute
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Use a gas inlet adaptator  They come with taps or without. You need the ones
with taps if you intend on evacuating your setup befotre introducing the argon, which is the best way to proceed to eliminate any atmospheric O2 or
H2O: evacuate your setup for 30-60s (or until your solvent, if you have one in there, starts to boil), then clsoe vacuum, open argon inlet until setup
is slightly overpresurized, and repeat the evacuation/refill a few times.
having a security over-pressure valve is a good idea, to avoid flying glassware if you don't clsoe the valve correctly, or if it has a leak.
Depending on how sensitive your reaction is, having a blanket of argon and a CaCl2 guard on top of your condenser cna be sufficient. Simply let stream
of argon pass when you open the setup to introduce or withdraw reagents/samples. This isn't sufficient for reactions sensible to O2, as you must used
degassed solvents (preferably distilled).
But it works for grignards for example. I guess you could get away with a LAH reduction too, but working with degassed/distilled solvents isnures that
they are totally dried, and they cna be transfered using canulas or syringes. I think aldrich published a very nice bulletin on handling
moisture/oxygen sensitive reagents.
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
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Picric-A
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cool thanks for that Klute and Magpie, i can buy a gas inlet tube for about £2 so that doesnt seem hard to get.
The gas bottles i will buy are £10 for 600g of argon, no idea how big this is... most of the money is in the £35 regulator 
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Picric-A
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I have just thought, slightly off topic but still on topic at blanketing gasses' could helium be used for a inert gas?
These can be bought readliy and fairly cheaply at baloon shops and they alredy have a regulator built in... just a thought
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ScienceSquirrel
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| Quote: | Originally posted by Picric-A
I have just thought, slightly off topic but still on topic at blanketing gasses' could helium be used for a inert gas?
These can be bought readliy and fairly cheaply at baloon shops and they alredy have a regulator built in... just a thought |
Helium is lighter than air so tends to leave the flask when a stopper is removed and it diffuses through Parafilm etc.
Carbon dioxide was quite popular as a blanket gas in the early days of air sensitive chemistry as it is heavier than air but it is quite reactive with
Grignards etc so has been supplanted.
Nitrogen is OK and it is used in some undergraduate labs but it is roughly the same density as air so not a really good choice.
Argon is tops for air sensitive chemistry, very unreactive and denser than air. A gentle flow of argon into your flask will result in a 'blanket' over
your air and moisture sensitive material that will exclude the nasty Earth atmosphere
However helium is a lovely sparging gas for HPLC!
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Picric-A
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HPLC?
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ScienceSquirrel
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| Quote: | Originally posted by Picric-A
HPLC? |
High Pressure Liquid Chromatography.
Very important in analysis and can be run on a preparative scale.
Not cheap but most of the people picking up the bills for this sort of kit are multinational drug companies so a few million here or there is not a
lot.
[Edited on 27-8-2008 by ScienceSquirrel]
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Klute
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Helium is pretty commonly used as an inert gas, but obviously argon is better suited IMHO for the reasons ScienceSquirrel pointed out. It is not
uncommon to see helium used in litt procedures, although less in the recent (<10years) ones.
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
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Picric-A
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cool thanks for clearing that up with me
| Quote: | Originally posted by Klute
evacuate your setup for 30-60s (or until your solvent, if you have one in there, starts to boil), then clsoe vacuum, open argon inlet until setup is
slightly overpresurized, and repeat the evacuation/refill a few times. |
Now i think about it surly it doesnt matter how dense the gas is if all you are doing is using it to fill a vaccum, it reminds me of diffusion of
bromine in a vaccum
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Jdurg
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| Quote: | Originally posted by Picric-A
I have just thought, slightly off topic but still on topic at blanketing gasses' could helium be used for a inert gas?
These can be bought readliy and fairly cheaply at baloon shops and they alredy have a regulator built in... just a thought |
That would not work too well. As already mentioned, He is much less dense than air so it will not form a "blanket" on top of your reaction and
oxygen, carbon dioxide, etc. can seep in. Also, He is so small that it has a pretty easy time leaking out through joints in your apparatus that
aren't completely sealed.
Another no-no is that the helium you can get cheaply in party stores is not pure helium. Due to people breathing in helium to make their voices
higher pitched, small amounts of O2 (Up to 5% I believe) are mixed in with the He so that suffocation doesn't occur. That oxygen will completely mess
up any reaction you plan on doing. Pure He with no oxygen added isn't nearly as cheap.
\"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists of the unmistakable scent of broccoli, and usually
requires wiping afterwards.\"
http://maddox.xmission.com. |
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Ozone
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Since it came up, I should mention that:
If you run out of He for sparging your HPLC solvent...Do not try the Ar you have at the bench. I "degassed" some water and then pulled a vacuum on it
in the sonicator and got...An avalanche of gas! The outgassing continued for some minutes. It appears that somehow, Ar intercalates (or something?)
itself into water.
So, FYI.
Nice job Magpie! (with cannula technique: just make sure to have a second needle in the septum...I find its is good to have a gas delivery line with a
"T" in it that I can partially cover with my thumb in order to more carefully regulate the flow of gas)... And I am envious, Klute (nice manifold).
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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Picric-A
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cool thanks for the advise Jdurg, that wouldnt be good if you were trying to distill potassium under it
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watson.fawkes
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| Quote: | Originally posted by Ozone
If you run out of He for sparging your HPLC solvent...Do not try the Ar you have at the bench. I "degassed" some water and then pulled a vacuum on it
in the sonicator and got...An avalanche of gas! The outgassing continued for some minutes. It appears that somehow, Ar intercalates (or something?)
itself into water |
I would guess (but I haven't particularly researched it) that you're seeing van der Waals
forces. Argon has 3p orbitals which can be polarized. Helium, with only 1s orbitals, does not. Van der Waals attraction leads to an energy of a
surface interaction between gaseous argon and liquid water, which then leads to the stability of micro-bubbles.
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DNA
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Just some questions on Argon, I'm planning on buying a argon cylinder to do reactions under inert atmosphere and I have couple of choices:
2L including reducing valve = 197.50 euro (NL)
5L including reducing valve = 185 euro (DE)
10L including reducing valve = 267.5 euro (NL)
I prefer to buy it in the netherlands since I also live there and then I can even pick them up insted doing it by post.
Germany offers a bigger cylinder for a nice price too.
How long would one last with 2L cylinder, or otherwise stated how much gas does one use for an organic reaction approx?
Thanks in advance.
[Edited on 29-8-2008 by DNA]
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