Any way to test for contaminated gas?

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Has anybody come up with a method to test for contaminated gas that doesn't involve a large expenditure?
Reply:There probably is but I can't imagine it being cheap. Only way I've done it is when I have a suspected bad mix is to run a bead with it and without changing any parameters run another bead with a new bottle. If you happen to have two bad bottles it won't confirm anything but it's the only way I could do it. It was a bad mix I had btw, nothing but holes and spatter on a 75/25 mix (least what it was supposed to be)..............M
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Originally Posted by Weldordie

Has anybody come up with a method to test for contaminated gas that doesn't involve a large expenditure?
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Originally Posted by Oldiron2

It would depend on what the gas and the contamination both are and the level of the second. If argon and a high level of oxygen, a short piece of bare copper wire put in the bottom of a large test tube and the tube carefully flushed well with the suspect argon, the top capped without allowing atmospheric air in, and the tube's bottom heated well for a long time would show the formation of copper oxide. Low levels wouldn't be detectable that way but some wet chemistry methods where the gas is bubbled through a solution would. A water-quality lab could probably shake a sample with "pure" water and using an electronic sensor, analyze the water for any increased oxygen. This might be affordable.If water were suspected,  a piece of dry test paper with cobalt chloride would change from blue to pink as the gas was passed by it in a long tube.We once got a bottle that was supposed to be compressed air, but it wouldn't support the flame in a GC. Thinking the machine just had a leak somewhere, but  kiddingly playing "mad scientist", I gathered a sample of the gas in a beaker, lit a small piece of paper and plunged it into the flask, extinguishing it and thereby proved the bottled "air" wasn't air.If a bottle is hdrotested but not properly dried before being refilled with inert gas, water would be a problem if used for welding.
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Originally Posted by mrmikey

There probably is but I can't imagine it being cheap. Only way I've done it is when I have a suspected bad mix is to run a bead with it and without changing any parameters run another bead with a new bottle. If you happen to have two bad bottles it won't confirm anything but it's the only way I could do it. It was a bad mix I had btw, nothing but holes and spatter on a 75/25 mix (least what it was supposed to be)..............M
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Originally Posted by Weldordie

I like your idea to run test beads, using side by side bottles... hadn't thought of that one.  That's what I will do, next.  I've bubbled the Argon (?) through pickling soda (calcium hydroxide) to test for CO2, and that one was negative.  I, then, grabbed a soda straw and blew bubbles in the liquid, and it turned milky, thus indicating the presence of CO2.My son suggested that I contact the science department at the HS to see if they might want to take on the project for science fair.I'm determined to get to the bottom of this any way I can.  It's been way too frustrating to purchase gas without knowing what the hell it is.
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Originally Posted by Oldiron2

What is it supposed to be, pure Argon? If doing TIG work, any chance water got into the gas hoses of the torch? Or have a leak near/in the torch head that's drawing air in?