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Concentrating Hydrogen Peroxide

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AndrewM

Tue Nov 15 2011, 11:49PM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

Sulaiman wrote ...

Due to the potential for bomb-making,
it would be prudent to not discuss the details of H2O2 concentration.
Especially here on 4HV.

I disagree; this is very interesting and has a home here in the Chemistry forum.

I've found 30% at Home Depot as a wood bleaching kit several times. I haven't looked in the last few years but you can apparently still buy it online, even in gallon quantities:

Even "mere" 30% is nasty stuff and will cause significant burns to skin. I hesitate to call them "severe", however, as it appears to burn only the outermost layer of skin which turns stark white and itches like crazy, but the damage to deeper tissue is nearly nonexistent in my experience.

To the question at hand - I should think you will have success at any temperature below boiling. Its really a matter of how patient you are - the lower your temperatures the higher your yield but the longer it will take. 70C should be no problem. Accelerating with airflow is a good idea. Other than that the comments above are good advice, no reason you shouldn't succeed.

Sophie Amelia

Wed Nov 16 2011, 05:21AM

Registered Member #4201 Joined: Wed Nov 09 2011, 07:42AM
Location:
Posts: 20

AndrewM wrote ...

To the question at hand - I should think you will have success at any temperature below boiling. Its really a matter of how patient you are - the lower your temperatures the higher your yield but the longer it will take. 70C should be no problem. Accelerating with airflow is a good idea. Other than that the comments above are good advice, no reason you shouldn't succeed.

Thanks for your help :) I managed to evaporate from 200ml to 50ml hydrogen peroxide. When i stored it overnight, there is this tiny floating thingies in the solution. Is it because it precipitates into crystals? if it is crystals, is it hydrogen peroxide cyrstals?

Thanks

AndrewM

Wed Nov 16 2011, 05:59AM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

Sophie Amelia wrote ...

Surely that is a question you can answer for yourself - can you find any evidence that H2O2 would be a solid at room temperature? Why would you suspect that a compound would precipitate without undergoing a chemical change?

My guess is that you introduced some contaminant, perhaps from whatever vessel you were using. You would do well to actually take the advice offered so far, particularly the bits about having clean smooth glassware.

Sophie Amelia

Wed Nov 16 2011, 06:49AM

Registered Member #4201 Joined: Wed Nov 09 2011, 07:42AM
Location:
Posts: 20

Conundrum wrote ...

One method I found out there "on the interwebs" for getting concentrated peroxide if you don't mind a bit of contamination is to take out the glass container from a large blue lightstick.
Put this aside, what you need is the fluid in the plastic tube (GOGGLES!!!!!)

I think there is some sort of stabiliser in the peroxide but it shouldn't be an issue.
The glass vial can be saved for later experiments as it contains the lumophore and phenyl oxalate ester.

So we can just extract out hydrogen peroxide from glowsticks? At what concentration is it usually at?

and why do i have to save the glass vial for?

Conundrum

Wed Nov 16 2011, 07:06AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Well, it contains a useful compound which can be used to make homemade OLEDs as well as use for leak tracing etc.
It fluoresces under UV nicely.

As I have no way to test the glowsticks I suspect it is fairly weak, probably around 9%.

BTW crystals should not form, this sounds very very dangerous and you need to ask an expert exactly what is
going on as they could be dangerously unstable.
(hence the whole "just buy it ready made and save the hassle" comments by others)

I suspect that they might be phosphoric acid as this is a common additive in drug store peroxide.

-A

cbfull

Tue Apr 03 2012, 07:53PM

Registered Member #187 Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140

The white, itchy patches that appear on your skin after exposure to hydrogen peroxide are not burns. It is called capillary embolism. As the peroxide absorbes into your skin, it encounters various catalysts that trigger decomposition. The white color you see is actually tiny oxygen bubbles trapped in your skin. Not really too dangerous on it's own, however it is extremely uncomfortable. It goes away in an hour or so.

As for concentrating, a little over a year ago I tried something that seems very promising.

You can't put dessicants (silica gel, drierite, 3A molecular sieve) directly into the solution, they decompose the H2O2 and I'm not exactly sure why. You can concentrate the peroxide by placing your dilute sample into a vacuum dessicator with lots of fresh dessicant and then applying vacuum.

When I tried this with 35% food grade H2O2, within a couple of hours I could tell that the dilute solution was decreasing in volume. After the volume had reduced to about half (next time I will use something with volume markings), the silica gel in my vacuum dessicator started turning sort of orange then dark brown. It seems that the peroxide itself was evaporating and doing something to the silica gel.

I am thinking that the next time I try this I will have:
â€¢ graduations on the container
â€¢ a tiny magnetic stir bar in the solution so I can stir it while it concentrates

Conundrum

Wed Apr 04 2012, 07:10AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Another method I've heard about is to bubble ozone through deionised water.
for this to work well you need to filter out the nitrogen oxides also produced, or you get a mixture of weak nitric acid and peroxide which is a "Bad Idea" (tm)

On a slightly different subject, many commercial washing powders (i.e. "OxiClean") have warnings on the bottle not to decant the powder into another container due to the risk of gas release and bursting.

Maybe someone can try backfilling a chamber with say helium, putting some wet OxiClean in there then ionising the resulting gas (basically oxygen) and bubbling through distilled water.
Controlling the reaction by dropping water a drop at a time using some sort of stopcock mechanism based on a magnet and coil.

-A

Forty

Wed Apr 04 2012, 04:48PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

I tried the slow heating process mentioned and it worked just fine, but it would take a lot of 3% H2O2 to make a decent amount of a more concentrated solution.

I was reading yesterday about arc reactions with air. Do dielectric barrier discharges and corona discharges still produce the oxides of nitrogen like a hot arc does? DBD seems to be the method of choice for ozone production in water purification processes. Do they use pure oxygen then?

I guess water electrolysis produces a small amount of ozone along with the oxygen, so that could be bubbled through water to slowly build up a H2O2 concentration.

A more effective way would be to collect the oxygen first and run it through a bunch of corona or DBD (a hot arc would probably just make the electrodes burn up.) That shouldn't be too difficult right? Does DBD require a low pressure?

edit: DBD seems to work just fine with STP air, I just tried it. Still not sure if it produces nitrogen oxides yet, so I'll try it in an enclosed container and look for a color change. The device is simply aluminum tape stuck to a piece of polycarb, segments of a zip tie glued to two sides for a spacer, then a 1mm thick piece of glass as the dielectric, and finally another piece of aluminum tape stuck on top of that. HV supply is a zvs driven AC flyback operating somewhere in the area of 20khz. Makes a lovely uniform ~2"x~1" sheet of corona/plasma.

Wastrel

Wed Apr 04 2012, 08:12PM

Registered Member #4095 Joined: Thu Sept 15 2011, 03:19PM
Location: England.
Posts: 122

I've read using a vacuum dessicator with sulphuric acid works well and can concentrate to well over 40%.

I think ozone destroys hydrogen peroxide so I'd be surprised if it's possible to build up a significant concentration this way.

I think silent discharges in air produce only a trace of nitrogen pentoxide and almost no lower oxides with the ozone around but they take a lot of energy for a given amount of ozone. Using pure oxygen produces the best yield.

Forty

Wed Apr 04 2012, 10:07PM

Registered Member #3888 Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649

Well I don't have sulphuric acid or a vacuum source (yet.)

Oh, I thought bubbling ozone through water was one way of making hydrogen peroxide. you're saying additional ozone will destroy the h2o2?

Another method I just read about that might be pretty straight forward is to concentrate it through freezing. h2o2 freezes at -0.4C, so a container of it submerged in a cooled ice/salt/water bath should freeze the water before the h2o2 and you could remove the ice as it forms to produce a more concentrated solution.

There are much fancier and more effective ways of concentrating it, but as per the OP and my own uses for it, ~30% would be a sufficient concentration for us amateurs.

Perhaps I should start a new thread in the hv section about DBD stuff, I'm curious as to what I can do with it.

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