# If hydorgen peroxide is left in an open container....
**URL:** https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046
**Category:** Factual Questions
**Created:** [August 17, 2011, 4:51pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046 "2011-08-17T16:51:04Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@janeslogin](https://boards.straightdope.com/u/janeslogin)
#### Post date: [August 17, 2011, 4:51pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/1 "2011-08-17T16:51:04Z")
If a retail concentration hydrogen peroxide is left in an open container does it decompose and evaporate or react with something and evaporate or just or evaporate … or what?
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### Author:  [@njtt](https://boards.straightdope.com/u/njtt)
#### Post date: [August 17, 2011, 5:15pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/2 "2011-08-17T17:15:31Z")
It will slowly decompose, giving off oxygen and leaving water, which, of course, will itself evaporate eventually.
Actually, I doubt that closing the container does very much to slow down the decomposition (although dust particles getting in the open top may speed it up a little), but it will stop the water evaporating.
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### Author:  [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)
#### Post date: [August 17, 2011, 6:44pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/3 "2011-08-17T18:44:12Z")
> [@njtt](#):
>
> It will slowly decompose, giving off oxygen and leaving water, which, of course, will itself evaporate eventually.
>
> Actually, I doubt that closing the container does very much to slow down the decomposition (although dust particles getting in the open top may speed it up a little), but it will stop the water evaporating.
Well, if sealing the container raises the partial pressure of oxygen in the headspace above the liquid then it should slow the decomposition reaction. Le Chatelier’s principle and all that.
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### Author:  [@randomface](https://boards.straightdope.com/u/randomface)
#### Post date: [August 17, 2011, 7:00pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/4 "2011-08-17T19:00:30Z")
This strikes me almost as homework help, but I’ll see if I can move the answer forward.
If it is left in an open container that isn’t opaque and the container is left in UV light, it will decompose much faster. The reason hydrogen peroxide is sold in brown bottles is to prevent the reaction that produces water and oxygen from being accelerated by light.
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### Author:  [@bordelond](https://boards.straightdope.com/u/bordelond)
#### Post date: [August 17, 2011, 7:21pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/5 "2011-08-17T19:21:39Z")
So … if I have a 5-year-old bottle of hydrogen peroxide in my medicine chest, that bottle is probably filled with water by now?
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### Author:  [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)
#### Post date: [August 17, 2011, 7:43pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/6 "2011-08-17T19:43:14Z")
> [@bordelond](#):
>
> So … if I have a 5-year-old bottle of hydrogen peroxide in my medicine chest, that bottle is probably filled with water by now?
Correct, it’s gone from mostly water to almost exclusively water.
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### Author:  [@Bill\_Door](https://boards.straightdope.com/u/Bill_Door)
#### Post date: [August 17, 2011, 7:44pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/7 "2011-08-17T19:44:58Z")
> [@randomface](#):
>
> This strikes me almost as homework help, but I’ll see if I can move the answer forward.
>
> If it is left in an open container that isn’t opaque and the container is left in UV light, it will decompose much faster. The reason hydrogen peroxide is sold in brown bottles is to prevent the reaction that produces water and oxygen from being accelerated by light.
If you really want to speed it up transition metals work best. Manganese dioxide works great at this.
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### Author:  [@janeslogin](https://boards.straightdope.com/u/janeslogin)
#### Post date: [August 17, 2011, 8:05pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/8 "2011-08-17T20:05:15Z")
Thanks. BTW, back when I was doing homework I would not have needed your help but half a century or more rather dulls the thinking a bit. I once read somewhere that geezers and students often write questions a similar linguistic style but I forgot where I read that.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [August 17, 2011, 9:25pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/9 "2011-08-17T21:25:06Z")
> [@](#):
>
> If you really want to speed it up transition metals work best. Manganese dioxide works great at this.
I’ve heard that silver is best. IIRC, the jetpack you sometimes see at big events is powered by silver-catalyzed decomposition of hydrogen peroxide.
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### Author:  [@randomface](https://boards.straightdope.com/u/randomface)
#### Post date: [August 17, 2011, 9:32pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/10 "2011-08-17T21:32:21Z")
Sorry for the semi-accusation. I saw your name with two questions that seemed similar to a question I got from my younger sister last semester asking for chemistry help.
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### Author:  [@voltaire](https://boards.straightdope.com/u/voltaire)
#### Post date: [August 17, 2011, 10:24pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/11 "2011-08-17T22:24:09Z")
From my own anecdotal evidence, this is correct:
> [@Bill\_Door](#):
>
> Well, if sealing the container raises the partial pressure of oxygen in the headspace above the liquid then it should slow the decomposition reaction. Le Chatelier’s principle and all that.
And this is incorrect:
> [@bordelond](#):
>
> So … if I have a 5-year-old bottle of hydrogen peroxide in my medicine chest, that bottle is probably filled with water by now?
>
> > [@Bill\_Door](#):
> >
> > Correct, it’s gone from mostly water to almost exclusively water.
I had at least 8 year old bottles of hydrogen peroxide in brown bottles stored in a moderately dark place that still displayed notable and impressive reactivity when put in contact with living tissue/blood.
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### Author:  [@thelabdude](https://boards.straightdope.com/u/thelabdude)
#### Post date: [August 18, 2011, 12:06am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/12 "2011-08-18T00:06:37Z")
Amines including the amino end of an amino acid also accelerate decomposition. Heat also.
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### Author:  [@Ruken](https://boards.straightdope.com/u/Ruken)
#### Post date: [August 18, 2011, 12:15am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/13 "2011-08-18T00:15:38Z")
> [@Bill\_Door](#):
>
> Well, if sealing the container raises the partial pressure of oxygen in the headspace above the liquid then it should slow the decomposition reaction. Le Chatelier’s principle and all that.
Only if the decomposition is reversible. I doubt it is. Even if it is, LCP doesn’t tell us that the forward reaction slows, but that the reverse reaction speeds up. The net result is the same though.
Does this dilute solution contain an inhibitor? The 30% stuff I use in lab does, but I don’t know about the solutions sold in stores.
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### Author:  [@california\_jobcase](https://boards.straightdope.com/u/california_jobcase)
#### Post date: [August 18, 2011, 1:33am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/14 "2011-08-18T01:33:40Z")
I had a chemical reference book at school that said commercial hydrogen peroxide solutions are chemically inhibited against spontaneous decomposition, and therefore are stable if uncontaminated. I just poured some from a bottle opened before 2004 onto my finger and also into the bathroom sink. It fizzed quite righteously under my fingernail and on the sink stopper. There’s definitely some peroxide left in there.
By the way- for all the tooth bleachers out there- I looked up carbamide peroxide (the active ingredient in tooth bleaching products) in that book. The entry said “see _urea_ peroxide”.
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### Author:  [@adianadiadi](https://boards.straightdope.com/u/adianadiadi)
#### Post date: [August 18, 2011, 3:31am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/15 "2011-08-18T03:31:27Z")
Hydrogen peroxide has higher bp than water and hence water is evaporated first leaving behind H2O2, whose conc. increases leading to more collisions between them. This increases the speed of decomposition of H2O2.
The dust particles also speed up the decomposition.
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### Author:  [@BigT](https://boards.straightdope.com/u/BigT)
#### Post date: [August 18, 2011, 5:13am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/16 "2011-08-18T05:13:03Z")
> [@california\_jobcase](#):
>
> I had a chemical reference book at school that said commercial hydrogen peroxide solutions are chemically inhibited against spontaneous decomposition, and therefore are stable if uncontaminated. I just poured some from a bottle opened before 2004 onto my finger and also into the bathroom sink. It fizzed quite righteously under my fingernail and on the sink stopper. There’s definitely some peroxide left in there.
>
> By the way- for all the tooth bleachers out there- I looked up carbamide peroxide (the active ingredient in tooth bleaching products) in that book. The entry said “see _urea_ peroxide”.
That’s what I was led to believe, too. In fact, I’m pretty sure one bottle I had actually mentioned a 0.1% belonging to a preservative of some sort.
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### Author:  [@bordelond](https://boards.straightdope.com/u/bordelond)
#### Post date: [August 18, 2011, 5:11pm UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/17 "2011-08-18T17:11:23Z")
> [@Ruken](#):
>
> The 30% stuff I use in lab does …
My assumption is “no”, but I’ll ask anyway:
Can that 30% stuff be used on cuts and scrapes if applied _very_ carefully? Not poured on, but maybe a few drops applied to a cotton swab? Or is it just too caustic at 30% solution?
I always forget that household hydrogen peroxide is heavily diluted :smack:
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### Author:  [@Grinfranklin](https://boards.straightdope.com/u/Grinfranklin)
#### Post date: [April 25, 2013, 12:29am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/18 "2013-04-25T00:29:27Z")
Here is my question: I have a favorite knife that I use for EVERYTHING in the kitchen. After each use I rinse and brush it off and put it in a glass with about half hydrogen peroxide and half water. How long should I expect the hydrogen peroxide to be effective in killing the germs or whatever on my knife?
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### Author:  [@johnpost](https://boards.straightdope.com/u/johnpost)
#### Post date: [April 25, 2013, 12:33am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/19 "2013-04-25T00:33:20Z")
if you wash the knife with soap and water it will kill germs. washing washes off germ food and kills germs that a rinse and soak likely won’t do.
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### Author:  [@Ruken](https://boards.straightdope.com/u/Ruken)
#### Post date: [April 25, 2013, 12:37am UTC](https://boards.straightdope.com/t/if-hydorgen-peroxide-is-left-in-an-open-container/593046/20 "2013-04-25T00:37:38Z")
> [@bordelond](#):
>
> My assumption is “no”, but I’ll ask anyway:
>
> Can that 30% stuff be used on cuts and scrapes if applied _very_ carefully? Not poured on, but maybe a few drops applied to a cotton swab? Or is it just too caustic at 30% solution?
>
> I always forget that household hydrogen peroxide is heavily diluted :smack:
I missed this back in 2011, but I wouldn’t put this stuff on you. It hurts and kills the skin it touches.
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