I do understand that chlorine bleach loses its potency over time. But is that in reference to sealed or unsealed (partly used) bottles, or both?

Sue

Take a look at this thread on eGullet.

I get the impression that the main issue is evaporation, so it seems that uncapped bleach would be useless pretty quick.

-john

thanks for the link. Very informitive.

Wow, that thread was chock full of nonsense.

As far as bleach losing it's effectiveness, let me put it this way. All bleach solutions (a combination of Sodium Hypochlorite and water) contain water right off the shelf. To say that water has some adverse effect on the solution is not supported by the facts. Contaminants in the water can react with the chemical to liberate some of the chlorine and weaken the effectiveness, and it will off gas and lose its concentration in an open environment, but if it is in a closed container mixed with clean water, it will not diminish any more than the initial dilution when it was put in the container. If you have it in a spray bottle, it will remain approximately as effective over nominal time usage as long as the seal is reasonably good and no contaminants are introduced.

Heating the solution doesn't directly effect the chemical, other than evaporating it, which if it is in a contained system will only recondense back into solution again. In the washing machine, hot water will evaporate the chemical out of solution quicker, but not at a rate sufficient to diminish the effectiveness of the application.

Sunlight can ionize the chemical, much the same as it does water, into it's elemental compounds (sodium, chlorine, hydrogen, and oxygen). Unless the sunlight is concentrated, this process is relatively slow.

Hi Benjammin,



Most threads are, here included! Welcome to the Internet! :-)

If you read the thread through, they do correct most of the mistatements people made and cover most of the points you bring up.

-john

Thank you for the information. It confirmed what I suspected but didn't know for sure.

I am in the habit of keeping a never-opened bottle of plain bleach with my jugs of stored water. Now I don't have to worry about it breaking down in time. If it's sealed so it doesn't evaporate, isn't exposed to direct sunlight or excessive heat, it's still good.

That's what I wanted to know. <img src="/images/graemlins/smile.gif" alt="" />

Sue

Sorry, Sue, maybe we're not done with this topic yet. A bit technical here...

I'm not a chemist so perhaps someone with a chemistry background out there can give me a thumbs up or down on this idea, but I thought that a slow reaction of HCl with Na+ ions gradually degrades the disinfecting power of bleach by reducing the concentration of hypochlorous acid (the source of the HCl), irrespective of whether any chlorine gas is allowed to escape from the bleach container. In this way, even an unopened, sealed bottle of bleach can gradually degrade over time. Comments?

By the way, here's a webpage from Cornell University with a response from Clorox about stability. It doesn't say whether we're talking about opened or unopened, but it does state that the concentration will diminish.

FWIW : found in chemistry books :

bleach ("eau de javel") will have lost half of its active component ("hypochlorite") after three years.

So if it loses it, where does it go???

Sue

Bleach is not stable.

excerpt from this web site :

Propri?t?s chimiques !
les eaux et extraits de Javel se d?composent lentement ? temp?rature ambiante avec formation de chlorate et de chlorure de sodium et lib?ration d'oxyg?ne.
3 NaClO --> NaClO3 + 2 NaCl
2 NaClO --> 2 NaCl + O2
La d?composition est acc?l?r?e par la lumi?re, la chaleur et la pr?sence de nombreux m?taux.... Les eaux de javel dilu?es sont beaucoup plus stables que les extraits.

(loosely translated ... or is it loosy translation ??? <img src="/images/graemlins/grin.gif" alt="" />)

Chemical properties :
bleach will slowly degrade at room temperature giving off chlorate, sodium chloride and oxygen (re formulae : NaClO = NaOCl)
Decomposition (or is it "Breaking down" ?) will be faster if light, heat or some metals are present.
Diluted bleach is more stable than extracts.
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another web page, in english
Physical properties

3.3.3 Description
.........
Boiling Point: Decomposes above 40?C (104 deg F)
...............
Odour chlorine (bleach) odour
Odour Threshold: Not applicable. Odour is due to
breakdown products such as chlorine.
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another one...
sodium hypochlorite
n.
An unstable salt, NaOCl, usually stored in solution and used as a fungicide and an oxidizing bleach.
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web page
Stability:
Slowly decomposes on contact with air. Rate increases with the concentration and temperature. Exposure to sunlight accelerates decomposition. Sodium hypochlorite becomes less toxic with age.
Hazardous Decomposition Products:
Emits toxic fumes of chlorine when heated to decomposition. Sodium oxide at high temperatures.
Hazardous Polymerization:
Will not occur.
Incompatibilities:
Ammonia (chloramine gas may evolve),amines, ammonium salts, aziridine, methanol, phenyl acetonitrile, cellulose, ethyleneimine, oxidizable metals, acids, soaps, and bisulfates.
Conditions to Avoid:
Light, heat, incompatibles.
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