BetaTest - 17-10-2011 at 15:13
Hi everyone!
I was hoping to get some advice on how to degas water. I know that in the laboratory setting a vacuum system of some type is used. I don't have access
to that equipment at home so I'm looking into other methods.
Can water be degassed by repeated boilings? I read on some webpages that by rapidly bringing water to a boil then letting it cool and repeating will
effectively degas it. Any thoughts on this? How many boilings will it take?
If repeated boilings don't work then is it possible to build a sufficient vacuum system at home (for around 30 or 40 dollars)?
Does anyone know of another method that I haven't mention? The only restriction is that the water still has to be safe for human consumption at the
end!
Thanks for reading!
BromicAcid - 17-10-2011 at 15:59
In college for quantitative analysis we degassed by boiling for a few minutes. We used this to make carbonate solutions.
Endimion17 - 17-10-2011 at 16:00
Hello. Boil it once and it's virtually free of gasses, but as soon you stop boiling, air begins to dissolve in it, if it finds its way to its surface.
So you can just put a wet rubber stopper on the boiling flask. It obviously has to be big enough so that teh atmospheric pressure won't jam it inside.
Don't remove the stopper until the very moment you need it.
Wizzard - 18-10-2011 at 05:25
Vacuum also works well.
SmashGlass - 18-10-2011 at 06:19
As above -
Boiling
Vacuum - even under water suction can be good enough.
Bubble Nitrogen gas or Argon through it. Removes oxygen.
Sonication
They are the most common scientific options.
*For the section below I hold no responsibility for your own personal safety.*
How about the home microwave! Ever heated water in a cup in that before? Then stopper it as posted lower...
Make sure the glass you are using is tough enough to hold under reduced pressure otherwise it's gonna implode once it cools.
Bad.
If you do it in plastic it might be interesting.... crush bottle. I don't know how well the bottle will hold up to being microwaved for that long
though.
An alternative musing would be to could boil the water on the stove then transfer to the plastic bottle using a funnel.
Leave a very small amount of space at the top. It's more of a home-brew technique but it could work theoretically.
Good luck.
Since boiling water at home is hopefully not considered a criminal activity these days?
Ozone - 18-10-2011 at 14:49
We usually do one of two things:
1. Sparge with He then serve under He pressure. For HPLC use, N2 or Ar are no-good! The solubilities of both in water are significant (20°C Ar ~0.06
g/kg, N2 0.018 g/kg vs He 0.0015 g/kg and O2 0.044 g/kg) which can lead to outgassing (see decompression sickness). If you merely need to exclude O2,
for example media for radical polymerization, then Ar or N2 should be fine. Water saturates at around 8 mg/L. See: http://www.engineeringtoolbox.com/gases-solubility-water-d_1...
2. Sonicate under vacuum and keep hot on a hotplate (also keeps algae from growing in it--which cause fits clogging frits 
)
3. Our newer instruments have built in on-line vacuum degassers. They are GREAT!
Cheers,
O3
BetaTest - 21-10-2011 at 17:32
Thanks for all the input guys!
I tried boiling (and double boiling) the water and it got me about 70% of the way there. So I just ordered this machine online:
http://www.foodsaver.com/product.aspx?pid=9568
My hope is to fashion that into a vacuum system. Does anyone think this will work? any tips?
Thanks!
[Edited on 22-10-2011 by BetaTest]
dann2 - 22-10-2011 at 05:30
An old refrigerator compressor will do as a Vacuum pump but perhaps it's too much bother.