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Producing oxigen

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DrZoidberg

Sat Apr 21 2007, 04:51PM

Registered Member #350 Joined: Mon Mar 27 2006, 05:14PM
Location:
Posts: 106

Hi,
Is there an easy way to produce oxygen without risking an explosion? If I just do it by electrolysis it's difficult to make sure no hydrogen gets to the oxygen side. Even a very small percentage of hydrogen can be explosive.
I read you can extract oxygen from the air by somehow separating nitrogen and oxygen. But how?
Using a membrane? Using magnets since oxygen is paramagnetic and nitrogen diamagnetic? Or some other way?

Bored Chemist

Sat Apr 21 2007, 05:13PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

The decomposition of hydrogen peroxide with manganese dioxide is traditional, but not cheap.
What do you want the O2 for?

Electroholic

Sat Apr 21 2007, 05:21PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

its easy to do electrolysis of water and get o2 and h2 seperately, most of the cells are cabable of that. only problem is that they will be slightly wet.

and if you have access to LN2, you can condense air and get LOX, lil bit dangerous tho.

HV Enthusiast

Sat Apr 21 2007, 05:24PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Are you interested in producing oxygen just for the sake the method of producing oxygen, or do you actually need oxygen for an experiment? If the latter, you can get small cylinders of O2 for next to nothing at your local gas supplier or welding shop.

ConKbot of Doom

Sat Apr 21 2007, 06:28PM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

EastVoltResearch wrote ...

Are you interested in producing oxygen just for the sake the method of producing oxygen, or do you actually need oxygen for an experiment? If the latter, you can get small cylinders of O2 for next to nothing at your local gas supplier or welding shop.

I'm not sure where the original poster is, but in the US at home improvement stores (home depot and lowes), you can find small cylinders of oxygen the same size as a handheld propane torch cylinder. Meant for small soldering/brazing torches.

GreySoul

Sat Apr 21 2007, 08:03PM

Registered Member #546 Joined: Fri Feb 23 2007, 11:43PM
Location: Albuquerque, NM
Posts: 239

I guess it depends on how much you need. Those little oxygen cans at home depot/lowes/etc are cheap relative to the cost of say, a car.... but it's still way over priced oxygen if you need more than the occasional small cylinder.

if you need small amounts of reasonably pure oxygen at low pressures and flow rates, on a regular basis, then you can get an Airsep style decertified medical oxygen concentrator for around $300 (look on ebay). they put put around 6-10l/h at 95-98% purity.

If you need higher purity, flow rates, and/or pressure then get a welding cylinder. Get the industrial stuff, medical oxygen is the exact same product in a different package - the extra cost is for SS fittings and certification papers.

tanks are usually available in these eizes:
D cylinders - 15 cubic feet
E cylinders - 24 cubic feet
M cylinders - 122 cubic feet
G cylinders - 244 cubic feet
H or K cylinders - 250 cubic feet
T cylinders - 337 cubic feet

a bigger tank, like a K or T should be around $15-30 a fill + deposit on the tank. You'll have to buy an oxygen reg, another $50-100. Sometimes you can rent/borrow one from the welding suppliers.

If you need more volume, higher flow rates, or cryogenic gases then do what I do...I buy 160L dewers of liquid oxygen for $75 a fill from Air Gas. (plus delivery + hazmat) I don't know how big those cans are from home depot, but my guess is there's several hundred, perhaps a thousands, of those cans in a full dewer. 160L LOX = ~4,860 cuft of gas.

...

have fun, and be careful with oxygen - it's toxic in high concentrations, and while it's not explosive or flammable itself, it lowers the combustion temps of things around it.

-doug

Polar

Sun Apr 22 2007, 02:18AM

Registered Member #660 Joined: Fri Apr 20 2007, 07:36PM
Location:
Posts: 8

If your local dollar store has sodium percaronate (around 30%) for about $1/lb, that and MnO2 should work well. The MnO2 can be had from "heavy duty" batteries.

If you are interested in going an electrolytic method, you could use sodium chloride, steel cathode, and glassy carbon anode. You could make sodium chlorate, and some at the anode, but it would be mixed with Cl2. Oxygen can be obtained by thermal decomposition of NaClO3, however, could be quite dangerous. Large crystals of NaClO3 tend to crack with a great force, possibly great enough to shatter a test tube, and chlorates in metal are not a great idea.

Also, depending on how much oxygen you need, you may be able to pick up an oxygen concentrator on ebay for cheap. I got mine for $77 shipped, but i looked around for it quite a while. It produces about 5 liters per minute (of around 90% O2), but the purity is not as high as you would get from the decomposition of an oxy salt.

DrZoidberg

Sun Apr 22 2007, 07:12PM

Registered Member #350 Joined: Mon Mar 27 2006, 05:14PM
Location:
Posts: 106

Thanks.
I only need a small amount of oxygen for some experiments. I think I will try to find those small cylinders.
I looked at ebay and found you can get oxygen concentrators there for less then 100 euro. So I will get one of those if I ever need larger amounts.

Dr. Shark

Mon Apr 23 2007, 01:04PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

A textbook way of producing oxygen on a laboratory scale would be decomposing hydrogen peroxide with a catalyst. Actually a lot of save chemicals give off oxygen when heated, for example potassium nitrate, so don't mess with chlorates!
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