# How Long Does Hydrogen Peroxide Last Once Mixed



## The King of Spain

I've not long been using Hydrogen Peroxide as a sanatizer. I have a spray bottle mixed from last weekend but wonder if its any good. How long does the breakdown take?


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## razz

Morning Deaves, we were discussing sanitisers not long ago, my suggestion was to check the viability of the mix by checking it's pH. You would need to check a batch when fresh so you have a benchmark to start with.


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## The King of Spain

> razz said:
> 
> 
> 
> Morning Deaves, we were discussing sanitisers not long ago, my suggestion was to check the viability of the mix by checking it's pH. You would need to check a batch when fresh so you have a benchmark to start with.
Click to expand...

Thanks


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## Wortgames

It depends on how clean (or dirty) the water is you mixed it with.

Distilled or deionized water will last indefinitely (that's what it is made with) but tap water contains impurities that will react with the H2O2 and make it less effective over time.

To be on the safe side I would use any tap water mix within a couple of days.


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## Ross

WortGames said:


> It depends on how clean (or dirty) the water is you mixed it with.
> 
> Distilled or deionized water will last indefinitely (that's what it is made with) but tap water contains impurities that will react with the H2O2 and make it less effective over time.
> 
> To be on the safe side I would use any tap water mix within a couple of days.



I agree with Wortgames. Though I tend to keep my spray bottle longer if made with tap water & just up the mix rate.

Cheers Ross


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## mobrien

Hi guys,

I thought I had some timeframes for H2O2 decomposition in one of my chem textbooks, but its seems I don't.

However, some info for you:

a) H2O2 does decompose over time, the chemical reaction is:
2H2O2 --> 2H2O + O2

That is it produces water and oxygen.

While a slow reaction, I can tell you that a 90% bottle of H2O2 won't be 90% after a year - more like 70% or so.

B) Decomposition is controlled by three main thing - temperature, pH and contaminants (especially metals which cataylise (speed up) the rate of decomposition)

Temperature - for each increase in 10 degrees C, the rate of decomposition increases by 2.2 x - so keep it in the fridge!

pH - if the pH is above 6 or so, the rate of decomposition increases

If the water has metals such as magnesium, iron or copper in it, decomposition rate will also increase.

c) You can tell the concentration of a H2O2 solution made with pure water using the following (correct at 25%):

pH Conc
7 0
5.3 10
4.9 20
4.7 30
4.6 40
4.5 50-70

Hope this helps,

Matt


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## Ducatiboy stu

An easier way is if you have a cut or some blood, spray it on. If it foams then it will be viable.

If you kept it in the fridge it should easily last a week


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## SpillsMostOfIt

Once it has stopped being useful as peroxide, it is still useful as rinse water as it is probably about as sanitary as any other water you have lying around. I know this doesn't give you a lot, but it means you get at least one use out of any water you pull from the tap...


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## Norsman

Ducatiboy stu said:


> An easier way is if you have a cut or some blood, spray it on. If it foams then it will be viable.


Are you promoting self mutilation stu?  
I suppose this is acceptable, it is after all for the sake of beer. :beerbang:


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## Ducatiboy stu

Norsman said:


> Are you promoting self mutilation stu?
> I suppose this is acceptable, it is after all for the sake of beer. :beerbang:




Of course one must lose an arm for the sake of good beer... :lol: 

I though everyone lopped off a finger just to test their peroxide solution... B)


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## frogman

Ducatiboy stu said:


> Of course one must lose an arm for the sake of good beer... :lol:
> 
> I though everyone lopped off a finger just to test their peroxide solution... B)




I did for the fits 10 tests now have to drink straigt from the taps as I can't pick-up my glass.

FROGMAN.

P.S. Typing with my nose also sucks.


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## Ducatiboy stu

frogman said:


> I did for the fits 10 tests now have to drink straigt from the taps as I can't pick-up my glass.
> 
> FROGMAN.
> 
> P.S. Typing with my nose also sucks.




HTFU... B)


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