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Concentrating Hydrogen Peroxide

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Sophie Amelia

Wed Nov 09 2011, 08:01AM

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

Hi!

I really need help with concentrating 3w/w% hydrogen peroxide. i cant really find any procedures on the net for it. I am trying gradual evaporation but at what temperature do i set my hot bath? Also, when i heat it up, bubbles start to form and that means it is decomposing :(

Does anyone know of any procedure as to how to do selective evaporation? I would be extremely happy if i can increase the concentration to at least 20%

Thanks a lot :)

Sophie Amelia

Wed Nov 09 2011, 08:25AM

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

ooh also right, if i want to have high pressure released by a 3wt/wt% hydrogen peroxide, what temperature of H2O2 and at what molarity of potassium iodide should i use? Thanks in advanced! :)

Nick

Thu Nov 10 2011, 02:36AM

Registered Member #4180 Joined: Thu Nov 03 2011, 01:32AM
Location: The first coast
Posts: 4

Just letting it evaporate is the best method, some people have boiled it with success. You can usually buy 35% hydrogen peroxide in organic grocery stores, check out this site:

, it has a list of all stores that sell it. If you don't have any luck you can order it off the internet. It's worth it, concentrated drugstore h202 isn't that great.

Ocean Waves

Thu Nov 10 2011, 07:09PM

Registered Member #4181 Joined: Thu Nov 03 2011, 02:39PM
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Posts: 42

I vacuum boiled mine with a double boiler in a suspended 4 liter flat bottom flask for surface area, kept it at around 134F under a pressure of about 50-100 torr, with very good results, i used a 1/4 Hp clear water pump and a vacuum aspirator in an endless loop with a 5 gallon reservoir for a my vacuum source took. 2 liters concentrated down to about 200 ml in 6 hours with this method with very little losses. Just make sure you acid wash your flask with hot concentrated nitric acid and distiled water to remove any organic or metallic impurities or you peroxide might decompose if you plain to go past 35% to 50 â€“ 60%, I doesn't go much beyond 60 percent with a simple low temperature/pressure boiling, going any further requires special glass ware.........

of course there is places to just buy 35% now so I haven't done this for a year or so......since hydroponics stores became popular they either have it or can order it for you without the ridiculous hazmat fee.

Sophie Amelia

Fri Nov 11 2011, 02:19AM

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

In my country, we are not allowed to buy concentrated hydrogen peroxide for educational purposes. Hence, i have to buy 3wt% from pharmacy and concentrate it myself

is it ok to put 200ml of H2O2 into a hot bath set at 70 degree celsuis? Because i tried it and after 4 hours, it lost about 50ml. Should i do titration to test out the concentration of hydrogen peroxide? or should i just use M1V1 = M2V2 to find the final concentration??

ooh and someone please help me with my previous question: "ooh also right, if i want to have high pressure released by a 3wt/wt% hydrogen peroxide, what temperature of H2O2 and at what molarity of potassium iodide should i use? Thanks in advanced! :)"

<3

Wastrel

Fri Nov 11 2011, 01:15PM

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

I can't recommend concentrating your own on health grounds or convenience grounds and starting with impure OTC 3% is asking for trouble. You need eye and skin protection for hot peroxide and for cold peroxide of higher concentration. If you can buy "30 volume" peroxide and have to concentrate, I recommend starting from that, it's about 9%.

The glass container needs to be very clean and as neer to scratch free as possible. You also need to be sure it won't shatter, I used a jug from a coffie maker on the makers hotplate. Heating below the boiling point in a strong air current is the method I used, which means it decomposes more slowly than just boiling. I think I was around 80C with only a small stream of bubbles from minor scratches on the glass. You will want to be upwind as the fumes are nasty. I did this in a kitchen and the extractor on full wasn't good enough, stinging eyes etc. Impurities and stabilising agents will concentrate with the peroxide and can make it unstable, the weaker the starting solution the worse this problem will be.

What boils off isn't pure water, but a water peroxide mixture which is weaker than the solution. Some decomposition also occurs. If you need to know the final concentration, titrate or decompose and measure the volume of gas that comes off to get an idea.

klugesmith

Mon Nov 14 2011, 11:40PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Wastrel wrote ...
If you can buy "30 volume" peroxide and have to concentrate, I recommend starting from that, it's about 9%.

I came to understand the "volume" rating of diluted H2O2 in pre-Internet days, but was probably older than the median reader of this forum today.
It's based on a simple assay method: 1) Bring a sample of H2O2 solution together with a catalyst. 2) capture all the resulting oxygen gas at atmospheric pressure, and take the ratio of its volume to that of the original liquid solution.

Sophie wrote:
>> Should i do titration to test out the concentration of hydrogen peroxide? or should i just use M1V1 = M2V2 to find the final concentration??

See above, or get a hydrometer for the appropriate range of specific gravity, or an accurate scale and volumetric flask. You can always take your concentrated product and see how much dilution it takes to match the material you started with.

Sulaiman

Tue Nov 15 2011, 06:35AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

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

Conundrum

Tue Nov 15 2011, 09:33AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Indeed, I second that.

That said, it IS inconvenient as hell to have to buy 3% because 9% is verboten and use 3* as much in your homemade PCB etchant.

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.

-A

Sulaiman

Tue Nov 15 2011, 12:54PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

There are so many copper etchants,
cheap/available = sodium hydroxide/caustic soda for drain unblocking etc.

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