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How do I know that's CO2 in that tank?

Came across a full #20 tank by trading a friend one gallon of Maibok for it. He could not tell me if that was really CO2 in that tank, as he did not fill it, he said his Dad found it. It has the right label, is in good condition with no dents, just a little dirty with that lint/grease dirt that tells me it hid in the backroom of a restaurant somewhere beside their soda kegs.
Is there an easy way to tell at home? Or should I just haul it down to my localk ARCET and see if they can tell me?


You can test at home with a calcium hydroxide solution. Mix about a teaspoon into up to a gallon of distilled water. This will make a saturated solution, so some of it won’t dissolve. Let it sit several hours or overnight, and then filter it through a coffee filter until it’s a clear solution. When you bubble CO2 through the solution it will cause it to turn cloudy due to precipitation of calcium carbonate. If it’s oxygen or nitrogen, the solution will stay clear.

You might see calcium hydroxide being sold in grocery or hardware stores as pickling lime or slaked lime.

I would just open it up and empty it and then take it to a welding shop - for $16 or so you can get it re-filled and not worry about it.


Another option is a fire extinguisher supply/service shop.

Thanks All, for the answers. I was wondering, I have 3 places in town I can fill up at. ! is an extinguisher shop, the other 2 are welding shops. Both welding shops also have “Medical Grade” CO2, which is supposedly filtered and cleaned. Isn’t plain old-plain old good enough?


just bring it to a shop, Airgas, welding, whatever and get it exchanged for co2

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