zombiedude1
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Concentrating H2O2 (17.5% - 30-35%)
I have been searching for a while, but could not find information relating to concentrating hydrogen peroxide to 30-35% while starting with 17.5%.
The methods I read were freezing, or warming up right before boiling point to evaporate. They claimed from 3% to 15-20% concentration with the
freezing method. While a vacuum distillation can yield higher purity.
I have 1 quart of 17.5% H2O2 that I want to concentrate to an estimated 30-35%; I'd imagine using the heating method would yield more accurate results
than freezing, but as I've never attempted this before, what should I do to achieve this percentage somewhat accurately?
I'm not looking for anything higher than 30-35%.
I could concentrate with the heating method, then determine concentration and dilute as needed; but I'd rather have a straight shot
(Sorry for the novice question, as it's been discussed many times already)
[Edited on 29-10-2015 by zombiedude1]
[Edited on 29-10-2015 by zombiedude1]
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battoussai114
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1st: Peroxide gets exponentially more dangerous as you concentrate it.
2nd: Boiling is a bad idea, it will decompose to water and oxygen without carefull temp control.
3rd: method for concentrating is usually vacuum distillation.
Some reading material that should cover most of this stuff:
http://ilot.edu.pl/eng_prace_ilot/public/PDF/list_of_transac...
http://www.diyspaceexploration.com/purification-concentratio...
http://www.iasj.net/iasj?func=fulltext&aId=24682
[Edited on 29-10-2015 by battoussai114]
Batoussai.
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careysub
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From what I hear the street method is to place it in a current of warm (not hot) dry air to evaporate.
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zed
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There are a number of discussions of this process in the archives. Try the search engine.
As for producing a highly accurate accounting of your final concentration, some sort of titration may be required.
Concentrating H2O2 is fairly easy to do. The fellas tell me however, that there is usually some degree of decomposition during the process.
Some of the guys have produced very high concentrations of H2O2.
I don't know if there is a really simple, no titration method, to get where you want to go. Vacuum distillation at room temperature might get you
close, but alas H2O2 does have a vapor pressure, some may distill over.
https://en.wikipedia.org/wiki/Hydrogen_peroxide
Ah! Wiki tells us that the concentration of Hydrogen Peroxide may be determined by density measurement. Got a hydrometer?
[Edited on 29-10-2015 by zed]
[Edited on 29-10-2015 by zed]
[Edited on 29-10-2015 by zed]
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Upsilon
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It can easily be concentrated simply by heating the solution close to boiling for several hours (boiling agitates the hydrogen peroxide and speeds its
decomposition). Typical method involves taking typical 3% household peroxide and heating it until it has 1/10th of its starting volume to
theoretically produce 30%. In reality, due to decomposition you'll probably get somewhere between 20-25% but this is still perfectly fine for almost
anything requiring 30% H2O2. Make sure no foreign matter finds its way into the vessel during concentrating as these particles will catalyze the
decomposition. You will definitely need to titrate the product to know its exact concentration.
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Bot0nist
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Blow air through it with an aquarium pump. IIRC, Plante was able to get moderate concentrations with little or no heat using this method. Just UTFSE
to find it, and the many, many other good threads on peroxide concentration and titration.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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cyanureeves
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i tried plante's method using a coffee maker hot plate but let it evaporate more than 1/3 the volume and it ate up my aerator stone.
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battoussai114
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Quote: Originally posted by cyanureeves  | | i tried plante's method using a coffee maker hot plate but let it evaporate more than 1/3 the volume and it ate up my aerator stone.
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It was super effective!
Batoussai.
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OneEyedPyro
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I've used a large glass cake pan on a heating pad with PC fan blowing across the top to much sucess, it takes a couple days to evaporate 5L down to
500ml.
The only problem is that you can end up with dust in your peroxide if you're not careful.
[Edited on 30-10-2015 by OneEyedPyro]
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zombiedude1
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Of course I have hydrometers 
Interesting, I never found that information with specific searches... Yet, it's right there on wikipedia!
Great information here, with many methods, thanks to everyone who commented.
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annaandherdad
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I have found recently that I can buy 28% H2O2 for about $5/liter (in 4 liter sizes) at a hydroponics store. People use it to feed their plants
oxygen. I think buying 3% in a drug store and concentrating it would be much more expensive, not to mention a lot more trouble. Somewhat more
expensive but still concentrated H2O2 is available on Amazon or ebay. This may only be useful if you live in the US, I donno.
Any other SF Bay chemists?
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zombiedude1
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Checked my local hydroponics stores (online), and I don't have any concentrated H2O2 locally.
I'm not sure if you read the post or not, but I claimed I was starting with 17.5% as it's the highest I could purchase off eBay, which was $23 for 1
Liter "Food Grade" @ 17.5%. Seems fairly expensive. Yes, 3% would be a huge waste of time.
Anyone have any cheaper resources?
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Upsilon
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Concentrating 3% is still cheaper than buying straight-up 30%. I ordered a box of 12 household bottles of 3% for under $15 USD. That's more than 5.5L
- which theoretically gives you over 550 ml of 30%. Compare that to your bottle - yours costs $0.13 per mL of H2O2, while the household stuff I got
costs $0.09 per mL H2O2. Even with loss the 3% is easily the more economical option.
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zombiedude1
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How about the energy costs included though, if doing vacuum distillation?
Does it still outweigh the cost?
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Upsilon
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Vacuum pumps don't really use that much energy compared to other household appliances, but like I said above even that isn't entirely necessary.
Heating it to steaming for several hours until it is about 1/10th of the original volume will get you a reasonable concentration.
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aga
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There are many many references for this.
Seek and ye shall find.
Thread closed.
Edit:
Godammnit ! My superMod powers<sup>tm</sup> fail me yet again.
I swear there is a Kryptonite manufacturer on this board.
[Edited on 30-10-2015 by aga]
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kemster90
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Concentrating peroxide under reduced pressure any one know what will distill first using a vacuum flask used for vacuum filtration also need a cold
trap to condense vapor before it reaches the hand pumped vacuum
I can see how this set up could be made to distill nitric acid under reduced presure and lowered temperature 
[Edited on 26-1-2016 by kemster90]
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