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argon

Magpie - 16-4-2008 at 12:55

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?

MagicJigPipe - 16-4-2008 at 13:22

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?

tumadre - 16-4-2008 at 13:34

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

Magpie - 16-4-2008 at 14:07

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.

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]

vulture - 16-4-2008 at 14:39

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]

Klute - 16-4-2008 at 14:56

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.

MagicJigPipe - 16-4-2008 at 18:39

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]

o2cylinder.JPG - 35kB

Magpie - 16-4-2008 at 18:46

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]

MagicJigPipe - 16-4-2008 at 19:30

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!

Magpie - 26-8-2008 at 15:07

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.

argon cylinder.jpg - 109kB

Picric-A - 26-8-2008 at 15:17

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?

Magpie - 26-8-2008 at 15:25

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]

Klute - 26-8-2008 at 15:36

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.

Picric-A - 26-8-2008 at 15:42

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

Picric-A - 26-8-2008 at 15:44

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

ScienceSquirrel - 26-8-2008 at 15:58

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!

Picric-A - 26-8-2008 at 16:11

HPLC?

ScienceSquirrel - 26-8-2008 at 16:32

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]

Klute - 26-8-2008 at 17:35

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.

Picric-A - 27-8-2008 at 01:02

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

Jdurg - 27-8-2008 at 14:50

Quote:

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.

Ozone - 27-8-2008 at 19:36

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

Picric-A - 28-8-2008 at 03:31

cool thanks for the advise Jdurg, that wouldnt be good if you were trying to distill potassium under it

watson.fawkes - 28-8-2008 at 06:58

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.

DNA - 29-8-2008 at 04:13

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]

ScienceSquirrel - 29-8-2008 at 04:26

Quote:

Originally posted by DNA
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]

That all depends on the scale that you are working on and how sensitive your materials are.
Some things can be done under a simple argon blanket using an inlet and a bubbler and just flushing the flask with gas.
Other things require the full treatment, degassing the solvents to remove air and a constant positive flow of gas.

Klute - 29-8-2008 at 05:48

I know the ones sold in my area, having a approx. volume of 5L indicate 500L gas. Might be different pressures though. Justa sk for the filling pressure, and calcualte the volume at STP with PV=nRT.

DNA - 29-8-2008 at 06:13

They would be around 200 bars.
I'm planning on using them for BF3xEt2O/NaBH4 reductions and for LiAlH4 reductions.
Maybe some times for Pd/C reductions.
I think for LiAlH4 it is sufficient to gas the solvent with Ar and pulling it vacuum until it starts boiling but that doesn't need that much of Ar I guess.

A constant flow probably will only be needed while adding the chemicals and for maybe half an hour until it is refluxing at that time the reaction is pushing up solvent gasses up to halfway the condenser.

That way air is being excluded anyway, then also using a drying tube on top and also having put a Ar blanket over it in the beginning should do the trick I suppose

Klute - 29-8-2008 at 13:52

It can be safer to introduce a stream of argon when quenching excess LiALH4 to dilute the H2 to minimize explosion hazard. Same for diborane reductions (as you don't want to breath any expeled gas).

I'd love to hear about your diborane reductions. I'm plannign on reducing some teriary amides soon, and plan on trying LiALH4 and diborane from BF3.ET2O and NaBH4 in THF. Got to prepare and purify the amides first, which isn't easy :S

DNA - 30-8-2008 at 02:07

I already have done quite some reductions with BF3xEt2O and it is really great exept from the toxicity of the gasses.
DO and absolutely DO mix the THF and BF3xEt2O in portions else it won't work.
So add NaBH4 in flask and chill to 0*C then add 2ml THF then 0,5ml BF3xEt2O then again 2ml THF then again 0,5ml BF3xEt2O and so on.
If you would pour in all the THF and then later all the BF3xEt2O I have had several failures.
Quite good yield around 70-80% with the method I described, small detail but very important.

jarynth - 31-8-2008 at 03:40

Welding argon from the DIY store here comes in thin walled bottles (of the torch gas kind, same nozzle as well) at an affordable price (about $20 for about 1-2 liters compressed). Would this be suitable as an inert gas or would it still contain huge traces of water etc? Unfortunately I don't recall seeing purity details on the bottle. I might inquire with the manufacturer.

Klute - 31-8-2008 at 08:39

I use thsi kind of argon in small disposable low pressur ebottles, and have had no problem with humidity. I used a CaCl2 in-line drier at first, btu seeing that it hadn't cake dup even afetr several bottle's, I consider them as dry. Very sensitive reactions would surely require adequate purification though, to remove traces of CO2 (which is the major contaminant in mine), possibly H2O and O2. But if you have invested into schlenk lines, degassed and distilled solvents stillls, etc, you could just aswell throw in a little more money to get good argon from Air Liquide or similar...

Use of Ar

tapira1 - 6-9-2008 at 17:57

We use Ar baloons for reactions (even for big ones); in this way you can control how much you use (unless you need to vent som gaseous reaction product). Your argon is too expensive; you should check for other qualities, which also work well.

MagicJigPipe - 7-9-2008 at 13:11

Quote:

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.

I mentioned this elsewhere on the forum but I figured it can't hurt to say it again. The "party helium" sold at Wal-Mart in the US is 99.995% He. No O2 or air (no more than 0.5 mL/L anyway). This information came from the company that makes (fills) and distributes the containers.

[Edited on 9-7-2008 by MagicJigPipe]

chemrox - 7-9-2008 at 22:20

Don't screw around with those little oygen bottles! Get at least a 40 CF bottle or you'll be running down to the supplier for more gas before your experiment is finished. It's not maintaining the head that uses up gas but the sweeping and flushing steps. I use a 40. I started with a 20 and traded with my supplier for the larger tank. The smaller ones might be ok for H2 for a medium pressure machine.

redox - 5-6-2011 at 10:04

So I went to the welding store, and $210 later...
I own a 20 CF argon tank w/regulator!

JJay - 27-10-2017 at 10:45

I've been looking at picking up a small argon cylinder.

This one I think is a little too small, but it would function well in an inert gas setup, right?

https://www.grainger.com/product/GASCO-Argon-Calibration-Gas...

MrHomeScientist - 27-10-2017 at 11:40

It depends on what volume you are trying to inert. Someone here sent me a great paper, "The Manipulation of Air Sensitive Compounds" by D.F. Shriver and M.A. Drezdzon, that goes into great detail on this sort of thing. In chapter 2.2 it talks about how to inert a chamber via the purging method, which is likely what home experimenters will use. To summarize, inerting a chamber requires purging it with somewhere between 1 and 7 volumes of gas, depending on how well the gases mix. Also, rapid purging is more effective than slow purging, according to the paper.
For my homemade glove box, I assumed the worst case and purged through 7 volumes before working in it. I could figure this out because I bought a flow meter for my cylinder and so I know the rate of gas entering the box and the volume of the box.

I have a 40 CF cylinder that I bought from my local AirGas shop for this purpose. I haven't used it much, but it looks like 3-4 7-volume purges and the cylinder is gone. So your small cylinder might only be "one time use" depending on the size of your chamber.

Also, "inert" gas depends on what you are working with, of course. CO<sub>2</sub> might be inert enough for some applications. But argon is pretty cheap, once you get past the cost of the cylinder.

[Edited on 10-27-2017 by MrHomeScientist]

JJay - 27-10-2017 at 15:51

I will probably be using small volume glassware with inert gas, but my largest flask is 3L, and it would be nice to be able to use it with an inert atmosphere.

I'd like to play with some organometallics, so I can't use carbon dioxide as inert gas (otherwise I'd just make it). I will definitely have a look at that book if I can find it.