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Author: Subject: Hydrogen peroxide concentration by freezing I need to make 12% h2o2 from 3%
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[*] posted on 18-6-2011 at 14:31
Hydrogen peroxide concentration by freezing I need to make 12% h2o2 from 3%


Hi everyone!

I'm trying to make an at home tooth whitening gel that needs a final concentration of 6% hydrogen peroxide, when means I need a stock of 12%(1:2 dilution). My local drug store only sells 3% hydrogen peroxide. Now I know that I can buy 30-35% online very easily but the problem for me is it costs a lot. So I was reading another topic on this forum about people getting h2o2 to like 90% (not sure why) but they mentioned that you can get h2o2 to 62% by freezing. My question is how can I get 12-20% by freezing? I don't want it to get all the way up to 60% and I'm also not clear on the method (just place it in the freezer and take out the ice cubes?). Also after I'm done with the freezing concentration, how do I estimate the final concentration?

thanks to everyone who read this, any advice would be appreciated!
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[*] posted on 18-6-2011 at 15:24


15% H2O2 is 'typical' for me by the freezing method but 20% is doable. Example, 2 large bottles of 3% peroxide:

Open and drain half the contents of each bottle into 2 other STERILE and clean bottles of similar capacity. If possible, just use 2 empty peroxide bottles. Stick the 4 half-filled bottles in the freezer and leave for at least 12-24 hours. After the contents are COMPLETELY frozen solid, turn them upside down (in the freezer). Make sure they're capped well and don't let them warm up (leaving the freezer door open too long, etc.).

Have a clean, sterile plastic or glass bottle handy with a small funnel. Every hour or so, quickly remove one bottle at a time from the freezer but keep them upside down. Carefully uncap and pour the contents of the cap into your container. You'll typically only get a few drops at a time.

Read up on hydrogen peroxide safety! WEAR GLOVES AND GOGGLES. Make sure everyone in your house knows what you're up to. That way, the Mrs. or kids don't knock the containers over or get 'stung'. DO NOT PLACE THE FULL BOTTLES IN THE FREEZER.

Tank
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[*] posted on 18-6-2011 at 17:21


You can get 12% from any beauty or makeup store. Ask for 40 volume peroxide. I've found 'clairoxide' brand 40vol is 12%. If you don't wanna go in there, ask your mom!

BTW: It is quite pure, too!

[Edited on 19-6-2011 by ScienceHideout]




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[*] posted on 18-6-2011 at 19:48


Quote: Originally posted by m1tanker78  
15% H2O2 is 'typical' for me by the freezing method but 20% is doable. Example, 2 large bottles of 3% peroxide:

Open and drain half the contents of each bottle into 2 other STERILE and clean bottles of similar capacity. If possible, just use 2 empty peroxide bottles. Stick the 4 half-filled bottles in the freezer and leave for at least 12-24 hours. After the contents are COMPLETELY frozen solid, turn them upside down (in the freezer). Make sure they're capped well and don't let them warm up (leaving the freezer door open too long, etc.).

Have a clean, sterile plastic or glass bottle handy with a small funnel. Every hour or so, quickly remove one bottle at a time from the freezer but keep them upside down. Carefully uncap and pour the contents of the cap into your container. You'll typically only get a few drops at a time.

Read up on hydrogen peroxide safety! WEAR GLOVES AND GOGGLES. Make sure everyone in your house knows what you're up to. That way, the Mrs. or kids don't knock the containers over or get 'stung'. DO NOT PLACE THE FULL BOTTLES IN THE FREEZER.

Tank


So once the h2o2 is completely frozen and still in the freezer inverted, what causes the more concentrated h2o2 to thaw and drip down? Also how concentrated would you expect it to be (the 15% you mentioned)?

Thanks!
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[*] posted on 30-6-2011 at 20:54


So I took 16 oz of 3% h2o2 then froze and inverted. I ended up with about 8 mls of fluid. How do I estimate the concentration of the liquid I collected? Also how much should I expect to collect by this method?

Any advice would be most appreciated!
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[*] posted on 1-7-2011 at 03:18


Why not just buy ebay 35% H2O2 and dilute it accordingly?


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[*] posted on 1-7-2011 at 03:48


Quote: Originally posted by BetaTest  
So I took 16 oz of 3% h2o2 then froze and inverted. I ended up with about 8 mls of fluid. How do I estimate the concentration of the liquid I collected? Also how much should I expect to collect by this method?

Any advice would be most appreciated!


Decompose fully the H2O2 with a MnO2 or other proper catalyst and measure the volume of evolved O2 with an inverted graduated cylinder and quantify.

[Edited on 1-7-2011 by Bot0nist]




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[*] posted on 1-7-2011 at 11:29


You start with 3%, you hope to get 30% - ten times as concentrated, should be about 1/10 the volume of liquid.

As for the MnO2 decomposition for testing the strength, to determine how much solution to test remember that a 3% solution of H2O2 will generated 10 times its volume of O2, a 6% solution 20 times the O2, and so on with 30% generating 100 times its own volume of O2.

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[*] posted on 1-7-2011 at 16:36


35% is available in nursery stores and greenhouses for use in hydroponics... It's kinda expensive, at least where I am, but I bet it would still end up cheaper than freezing 3%.. Also search for "bacquacil"
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[*] posted on 1-7-2011 at 18:52


there is another thread that deals with h2o2 right here. i used their method by pouring the contents into a glass and waiting until 50% was frozen then i quickly filtered the ice with a coffee filter and kept the liquid. by the time i was done with two bottles my finger tips were bleached white. that stuff itches at first but then starts to burn non stop for about 30 sec. i dont know how concentrated it is but one drop will burn the palm of my hand until it leaves a white chalky blotch. i also used a burner at about 200 deg. and evaporated 2/3 of the liquid and got the same strength as freezing. i also left it out in the west texas sun inside a pickle jar and let it evaporate 2/3 and got mostly water. i guess it has to be evaporated quickly and just under boiling but i noticed that it could take more heat without bubbling after 2/3 was evaporated on the burner.it surprised me that the remaing 1/3 would hardly steam the side of the glass while heated.

[Edited on 2-7-2011 by cyanureeves]

[Edited on 2-7-2011 by cyanureeves]
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[*] posted on 1-7-2011 at 21:41


I believe zhmapper has a vid on u tub of him concentrating h2o2 by heating it gently so it doesn't decompose. I'm on my phone otherwise I woulda posted a link



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[*] posted on 2-7-2011 at 06:51


Check out this thread. http://www.sciencemadness.org/talk/viewthread.php?tid=15881

Me and tank went back and forth on the topic of freezing vs evaporation. While I never did the tests I mentioned, I still use the slow evaporation with a dry air stream/aspiration method.

[Edited on 2-7-2011 by Bot0nist]




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[*] posted on 4-7-2011 at 02:07


wow guys thanks to all for taking the time to reply. I'm going to try some version of the heat/evaporation when I get some time. For the moment what really has me thinking is the use of a catalyst and measurement of the evolved gas. It was mentioned earlier, that this could be done with an inverted cylinder... does anyone have a link or more information on how to properly setup such an apparatus?

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[*] posted on 4-7-2011 at 02:24


I seem to remember a similar topic being posted years ago in the E+W forum.
Apparently, solutions of H2O2 can be concentrated up to 62% (?) by freezing out the water, but after the solution reaches that concentration the H2O2 will begin freezing out; I do not remember the exact percentage, but I am sure it was somewhere between 60-80%. This was just a post I remember, cannot find any information about it now. I also cannot remember whether the poster said the H2O2 begins to freeze out with the water, or whether it begins to freeze out separately. I think it might have been separately, in which case it would be possible to obtain 85% + concentrations, but one would have to know the exact percentage at which the H2O2 would begin to freeze out, and have some way of measurement, to know when to discard all the water-ice crystals that had formed so that any additional solid that freezes out would be 85%+ H2O2.

[Edited on 4-7-2011 by AndersHoveland]




I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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[*] posted on 4-7-2011 at 05:24


this forum also talks about % on the other h2o2 thread but it is too much work for me. they said it is only a 1 deg. difference freezing point between water and h2o2. i had to make about 3 or 4 extractions because when the solution freezes to half it quickly thaws to 1/4 of ice and the just below boiling actually takes about 6 to 7 hrs. letting the sun do it took about 6 days and it was very weak.
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[*] posted on 4-7-2011 at 05:44


Don't use the sun, I would think the UV would increase decomposition. 4-5 hours to bring 500ml to <100ml with gentle heating (surface temp <=170F) isn't a raw deal. Using a little blower or aspirator speeds things up a good bit. Even using non-dried air from a fish tank blower knocks about an hour off.

Anders, I would think it would be very hard to get anything approaching high-test with freezing due to the diminishing variance in freezing points. Heating/evaporating also cant give you much higher than 25%-35% because as the solution becomes more concentrated, more heat is required to drive of the water. More heat = more decomposition.

All in all the best bet is to just buy 30% food grade. It is readily available in most places. If higher concentrations is needed, just pull a little vacuum on it and boil off the water. Be careful though. anything over 70% is very wicked I would imagine, and I bet anything approaching 90% could undergo explosive decomposition with the slightest provocation. (ex. dust or crud in the glass, etc, etc.):o

[Edited on 4-7-2011 by Bot0nist]




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[*] posted on 4-7-2011 at 18:22


I also had the idea of adding acetone peroxide (diluted in pure acetone for safety) to water. After several days in the dark, the acetone peroxide should hydrolyze into acetone and hydrogen peroxide.
The hydrolysis is catalyzed by dilute acid- but too acidic and the equilibrium does not favor any change.




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[*] posted on 5-7-2011 at 05:23


Quote: Originally posted by BetaTest  
wow guys thanks to all for taking the time to reply. I'm going to try some version of the heat/evaporation when I get some time. For the moment what really has me thinking is the use of a catalyst and measurement of the evolved gas. It was mentioned earlier, that this could be done with an inverted cylinder... does anyone have a link or more information on how to properly setup such an apparatus?



Decompose the peroxide and lead the gas into the inverted cylinder filled with water. Measure the volume of gas that displaced the water.





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[*] posted on 5-7-2011 at 16:57


Botonist's drawing sums it up; I'll just add a few points:

If you don't have a graduated cylinder, use any type of clear container of known and uniform inner diameter. Run a piece of electrical tape from top to bottom (lengthwise). Use a sharpie to mark the initial water level then make another mark after the decomp. Measure between the 2 marks and calculate the volume of water displaced.

My decomp container allowed me to load the MnO2 into a bent plastic "J" tube (attached to the lid) so that I could seal the container before contacting with the peroxide. You could probably get away with pouring the peroxide and then dropping a smaller tube containing the catalyst in the chamber. Once sealed, tilt or shake a little to release the catalyst.

Dilute the peroxide in such a way that it won't decompose so fast as to warm the mixture (give false results). On the other hand, you don't want it to be so diluted that it takes a long time to complete the test. It should take no longer than 3 minutes.

After the initial stream of bubbles dies down, swirl the decomp container but make sure you don't squeeze the bottle (if it's plastic). Again, this will give false results.

It may take a few trial and error runs before you get it dialed in. Be sure to rinse all of the MnO2 out after each test.

+++++++++++++++++

Quote:
So once the h2o2 is completely frozen and still in the freezer inverted, what causes the more concentrated h2o2 to thaw and drip down? Also how concentrated would you expect it to be (the 15% you mentioned)?

It doesn't really freeze at all. It gets trapped within the ice crystals and slowly makes its way down through the ice. Cold, concentrated peroxide sticks to surfaces better than water (you may have noticed that when emptying the peroxide bottle caps) so it takes time and never completely drains. You might be tempted to tap or bang the bottles before you uncap them. Doing so will knock small chunks of ice into the cap, diluting the harvest.

My minimum has consistently been 12% while my maximum concentration is usually 18%. I've been rewarded with 2 or 3 20% harvests by being very careful but it isn't worth all the trouble to squeeze out an extra 2%. I almost always dilute down to 12% anyway so it works out.

Tank

[Edited on 7-6-2011 by m1tanker78]
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[*] posted on 5-7-2011 at 18:26


Good idea with the "bent plastic "J" tube" attachment.

About the raise in temperature, I also worried about that. I guess adding the catalyst slowly to allow time for heat dissipation would help keep things STP. I thought of adding the H2O2 drop-wise into a catalyst bed, but that may even get hot enough to steam. I wonder if a simple way could be devised to add the MnO2 a little at a time, while keeping a sealed chamber. Maybe some variation on the "J" attachment.

Maybe a large, room-temperature water bath would work?

I need to stop armchair experimenting and do some trials I guess...

[Edited on 6-7-2011 by Bot0nist]




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[*] posted on 5-7-2011 at 19:36


Quote:
I thought of adding the H2O2 drop-wise into a catalyst bed, but that may even get hot enough to steam.

If your decomp gets too hot and/or proceeds too quickly then adjust the quantity of your unknown peroxide as well as how much water it's diluted in. For example, if 10mL of unknown peroxide + 30 mL water is giving you a run for your money, half the peroxide or double the water. Make sure you take note of the unknown peroxide quantity - the added water only slows the decomp but produces exactly the same quantity of gas at the end.

Don't use an excessive amount of catalyst. This generates unwanted heat as well. I may have already mentioned this: Don't forget to swirl (but not squeeze) the decomp chamber!

Tank
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[*] posted on 28-4-2013 at 15:40


Found some decent articles on increasing the molarity of H2O2 in solution.

Now can anyone think of a way to improve the sulphuric acid/vacuum pump model? Does H2O2 react with other absorbents, like H3PO4, MgSO4(anhydrous), CaCl2(anhydrous), etc? Then removal of the water from the mixture in the gas phase might be feasible, especially under vacuum, where the boiling point of the mixture would presumably be lowered appreciably.

Attachment: Maas.Herzberg.The.Properties.of.Pure.Hydrogen.Peroxide.II.pdf (152kB)
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Attachment: Maas.Hatcher.The.Properties.of.Pure.Hydrogen.Peroxide.III.pdf (536kB)
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Attachment: Maas.Sulfuric.Acid.Concentrator.and.Vacuum.Pump.pdf (320kB)
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Attachment: Mass.Hatcher.The.Properties.of.Pure.Hydrogen.Peroxide.I.pdf (1.6MB)
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[Edited on 28-4-2013 by aliced25]

Attachment: Sulaymon.etal.Concentration.of.H2O2.by.Batch.Distillation.Column.pdf (1.2MB)
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[*] posted on 2-5-2013 at 13:43


Or, you could just put some 3% on a dinner plate and allow it to evaporate.
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[*] posted on 2-5-2013 at 16:20


unless you live in a hot, dry climate, this takes days and days, even weeks, if ever, to get to >25%. After reading about the guy in Arizona, I tried it, (in Ga). No luck at all. Its was in a clean place with minimal dust too. After 5 day, only a very slight reduction of volume was observed. The evaperative proccess must be sped up with gentle heating and a dry, clean air flow over the surface. Mag stirring help to keep the heating even, and as long as the surface temp doesnt exceed ~180f, decomp is minimal.

Pouring a liter of 3% peroxide in a clean glass cassarole dish, and putting it in your oven, set to 170f does work though. After 8-12 hours the volume is reduced to around 50-80ml, and what remians is very close to 30% H2O2, so be carefull...

[Edited on 3-5-2013 by Bot0nist]




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[*] posted on 3-5-2013 at 09:27


since we are talking about it. is 130vol. H2O2 35 or 40%? in our cleaning cupboard I found a bottle with 1l 130vol that had cost 7eur. It was, however very old and nearly empty and I used to clean out my fish tank (After I removed the filters, heaters, fish and plants.
Is this conc. worth buying?




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