Mystery gas in CO2 tank?

I bought a used CO2 tank from some friends. It has a sticker on it that clearly labels it as "CO2" and had a broken Tap Rite regulator on it. It was also full. I thought my friends had said that they had it filled. Last night I hooked it up and poured some beer. Today I texted my friend and it turns out they had found it in a garage full and have no idea if CO2 is in it.

I filled my other tank and will take this one off when I get home. Since this IS a CO2 tank, with a beer regulator on it, should I be concerned? Is it legal/possible/probable to put a different gas in a CO2 tank?

Should I be concerned?

If you drink a glass and get the giggles, it's probably Nitrous Oxide.

I'm pretty sure if the tank says CO2 it's probably CO2. Other welding gasses might be Argon, Oxygen, Helium... Not sure how bad those things are for you or if they take the same thread direction/pitch/count as a CO2 tank. You might take it to a welding shop and ask them. If the gas smelled ok (DON'T sniff directly!) and the beer tasted ok, it's probably ok.

The beer did taste fine. My plan was to try and make dry ice with it to confirm that it's CO2.

I have read that Nitrogen and Argon need a much higher pressure tank. I just hope it's not oxygen and I'm not making 20 gallons of beer stale.

Yeah, Nitrogen is about 5k and Argon is usually around 2-3k. Both are stored as a GAS, not a LIQUID like CO2. They have to run tank pressure way up to get much volume in there.

Also, expelling liquid to make dry ice won't prove that you have CO2. You can make 'dry ice' with propane and lots of other bottled liquids with a really low boiling point.

I was able to make dry ice with it. I am sure you can freeze things with liquid propane, but it's not considered dry ice. I am not certain what I made was "dry ice" but it acted exactly how dry ice does with the outgassing.
I also filled a mason jar with the gas, and put a lit lighter into it. When it reached the rim of the jar, the flame instantly went out.
I think it's CO2. I was mostly afraid that it was oxygen or compressed air and that I had just made 20 gallons of beer go stale.

CO2 tanks use CGA 320 fittings, nitrogen/helium/argon use CGA 580, oxygen uses CGA 540. They are not interchangeable, and as long as the tank was filled at a legit place (not in some dude's basement...) there's pretty much no way they could accidentally put one in the other, and to do it on purpose would be illegal and a PITA.

Zachattack, you gave me the exact info I was looking for. Thank you.

bknifefight said:

I also filled a mason jar with the gas, and put a lit lighter into it. When it reached the rim of the jar, the flame instantly went out.
I think it's CO2. I was mostly afraid that it was oxygen or compressed air and that I had just made 20 gallons of beer go stale.

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sidenote: The open flame was extinguished because the gas displaced the oxygen/air. Many (if not all gases) will do this if in a confined space (such as a mason jar). This does not necessarily prove it is CO2.

Also, sticking a lighter into a jar of gas from an unknown cylinder is a pretty dumb move. If it had been oxygen (or hydrogen or acetylene), you would have hurt yourself in all likelihood.

broadbill said:

Also, sticking a lighter into a jar of gas from an unknown cylinder is a pretty dumb move. If it had been oxygen (or hydrogen or acetylene), you would have hurt yourself in all likelihood.

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Your concern is appreciated but I would have not done this if I wasn't 99% sure it was CO2

broadbill said:

Also, sticking a lighter into a jar of gas from an unknown cylinder is a pretty dumb move. If it had been oxygen (or hydrogen or acetylene), you would have hurt yourself in all likelihood.

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He MIGHT have hurt himself.

Oxygen would just make the match burn up real fast. It will not "explode".
Hydrogen wouldn't have stayed in the jar.
Acetylene, probably not a good idea, but it would have been a really really rich mixture, so it probably would have gone "poof" and then sat there and burned at the mouth of the jar as it was able to mix in oxygen from the air.

Again, not saying it was a good idea, just trying to limit the hysteria.