oxygen removing solution

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ri
Posts: 278
Joined: 01 Jun 2006, 10:00
State/Location: NSW

oxygen removing solution

Post by ri »

Hi All,
and welcome back to a new term.
Has anyone been asked to supply a sodium dithionite (sodium hydrosulfite) solution as a means for removing oxygen from water prior to photosynthesis and respiration experiments?
We need it for year 7, it is only approved for years 11-12, to be used with caution.
I would love to hear of a safer alternative...
Cheers,
~Robyn
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ELIZABETH
Posts: 233
Joined: 02 Jun 2006, 10:00
School: O'Connor Catholic College
Suburb: Armidale
State/Location: NSW

Re: oxygen removing solution

Post by ELIZABETH »

Hi Robyn,
A much easier alternative is to boil the water vigorously for about 5 mins immediately before use then cool it - no mess, no chemicals.
Liz
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Robb
Posts: 2062
Joined: 01 Jun 2006, 10:00
State/Location: NSW

Re: oxygen removing solution

Post by Robb »

Hi All,

A great method to de-oxygenate water or other gas containing liquid is to use a Ultrasonic Agitator. Essentially it is a shallow rectangular "deep Fryer" that contains water. When you turn the instrument on, it agitates the liquid using ultrasonic waves.

But some schools may not have this particular piece of equipment.

Cheers,

Robb.....
Dr Robert Crosdale. MRACI. NSS. NSSA. NASA.
Ph.D (Chem), Post Grad Ph.D (Physics), M.Ed, B.Sc (Hons), Dip. Appl. Sc. (Chem)
Lake Munmorah High School.
University of New England.
University of New South Wales.
University of Newcastle.

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lada
Posts: 1024
Joined: 29 Jun 2006, 10:00
State/Location: NSW

Re: oxygen removing solution

Post by lada »

No we do not have this contraption, but boiling the water is brilliant. If I store in in airtight container fiiled to the top, that should work well.
thanks Lada :coffee:
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ri
Posts: 278
Joined: 01 Jun 2006, 10:00
State/Location: NSW

Re: oxygen removing solution

Post by ri »

G'day all,
I am very in favour of the boiling water technique but our teachers are very sceptical.
Can you give me more details? How long did you boil it and how soon after it cooled did you use it? We need it (the oxygen free water) to turn methylene blue clear.
Thanks,
~Robyn
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Wombat
Posts: 11
Joined: 31 May 2006, 10:00
State/Location: NSW

Re: oxygen removing solution

Post by Wombat »

If you boil water to remove oxygen you will need to contain it so oxygen can not ingress back in ie. pour the just boiled water into a flask which you fill to the top so that when it is stoppered there is little or no air above the water while it cools.

Another way is to sparge water with oxygen free nitrogen gas (most school labs may not have nitrogen bottles)

Another way which I used to use when home bottling whiite wine was to add ascorbic acid. Ascorbic acid will scavenge dissolved oxygen. Oxygen dissolves to about 2x10-5 Molar in water, so I used to add ascorbic acid in order to make the wine 10-4Molar with respect to ascorbic acid. This gives about a five times excess over oxygen.
Before using this technique however you would need to be sure the excess ascorbic acid does not interfere with the processes you are studying.
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