Nitrogen or helium...

T

Trilobyte

Registered Senior Member
I'm doing a biology experiment that involves the respiration rate of yeast. I want to use an inert gas of some kind to reduce the oxygen concentration present in a controlled way ( by diluting it with something else).

The idea is to use a kind of bell jar with normal air trapped in it using a deep enough container off water. The inert gas (N or He) would then dilute the gas in the bell jar. (an oxygen probe would then measure the concentration present)

What I want to know is do you think I should use nitrogen or helium as the diluting gas. I would presume oxygen is more soluble in nirogen than in helium but helium is easier to get hold of (you don't need to buy it in huge tanks from industrial sources).

Could anyone point out any info on the solubility of oxygen or CO2 in helium and nitrogen? (I'm finding it very difficult to do a straight forward search for it- it is an awkward request ). Also any advice would be appreciated.
 
I don't know that solubilty applies between two gases... I had the impresion that all gases mix together equally well.
I'm surprised that helium is harder to get than nitrogen.
Have you tried a welding equipment supplier? They could also supply Argon, which might be cheaper choice than Helium.
 
Are you in Australia? Try your local BOC outlet. They have compressed nitrogen cylinders (size D - 76cm high, 15cm across) from $30 (although I guess you'll also need a regulator, hose, and stuff).
 
nitrogen wolud be bettre because of its density. helium would probably make your experiment float if you used too much, but it wolud take a lot more nitrogen to get it of the bench
 
Pete said:
I'm surprised that helium is harder to get than nitrogen.
Have you tried a welding equipment supplier? They could also supply Argon, which might be cheaper choice than Helium.
Click to expand...

No I said helium is easier to find than pure nitrogen.(eg party shops)

I did some more research and now realise that helium would be a waste of time because it would not stay mixed with air - it would just separate out into two layers of air an helium even if you cool it or lower the temperature. Nitrogen would be ideal if I could find it in small quantities but what about small quantities of argon? Is argon easier to find than nitrogen (in small quantities)?
 
you could break open some lightbulbs, if im not mistaken most are still filled with argon.
 
No need. Problem solved. Someone found some nitrogen. btw yes they are argon filled but I kind of need it in a usable container ...I suppose there is a way to capture it though...not that difficult actually...hmm...yes...[wanders off mumbling to himself].
 
Argon is quite expensive, due to the low temperatures needed to condense it out of the air.
In what way did you get hold of nitrogen?
 
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