# How safe is bleach to use?
**URL:** https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301
**Category:** Factual Questions
**Created:** [June 6, 2012, 6:55pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301 "2012-06-06T18:55:13Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Bamboo\_Boy](https://boards.straightdope.com/u/Bamboo_Boy)
#### Post date: [June 6, 2012, 6:55pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/1 "2012-06-06T18:55:13Z")
I remember hearing a long time ago that when bleach (household solution, such as Clorox) evaporates, it leaves only salt behind. Is this true?
My sister insists that it’s super harmful to use. I know that it is caustic, etc, and am aware of ventilation and contact issues. But she claims it is harmful to others _after_ I use it, after all is dried and all is said and done.
Is the claim about leaving behind only salt untrue? What’s the Straight Dope on this issue?
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### Author:  [@aceplace57](https://boards.straightdope.com/u/aceplace57)
#### Post date: [June 6, 2012, 7:35pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/2 "2012-06-06T19:35:23Z")
I spilled a bottle of bleach a few years ago. I discovered a very large puddle hours later. Mopped it up and rinsed the floor extra carefully. Didn’t harm the vinyl floor tile. I did open the window overnight to help clear out the fumes. I’ve used bleach on my white T-shirts and boxers for thirty years. Hasn’t killed me yet. 😉
You can always run them through an extra rinse cycle to remove any lingering bleach smell.
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### Author:  [@Inner\_Stickler](https://boards.straightdope.com/u/Inner_Stickler)
#### Post date: [June 6, 2012, 7:41pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/3 "2012-06-06T19:41:22Z")
Standard bleach is NaOCl in a solution of water. I guess I don’t know that much water evaporation. I would assume that the H[sub]2[/sub]0 would leave the solution all on its own an you’d be left with NaOCl. If you could add an acid and get some more H[sup]+[/sup] ions in there, you’d just have NaCl plus whatever came along with the acid. I dunno, though. I’m not a chemist.
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### Author:  [@Washoe](https://boards.straightdope.com/u/Washoe)
#### Post date: [June 6, 2012, 8:03pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/4 "2012-06-06T20:03:16Z")
I’ve been told several times that straight bleach will pit stainless steel. Any truth to this? I’ve tried it on scrap metal pieces and it didn’t seem to do a damn thing.
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### Author:  [@Kevbo](https://boards.straightdope.com/u/Kevbo)
#### Post date: [June 6, 2012, 8:34pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/5 "2012-06-06T20:34:27Z")
It can and is used in many cases to chlorinate drinking water. Larger systems will use chlorine gas, but many smaller systems use Sodium Hypochlorite solution…bleach.
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### Author:  [@njtt](https://boards.straightdope.com/u/njtt)
#### Post date: [June 6, 2012, 8:54pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/6 "2012-06-06T20:54:34Z")
There is more than one type of bleach, but no, regular hypochlorite bleach is not very dangerous, so long as you take sensible precautions as you seem to be doing.
If it was, they would not be selling it to the public, or at the least it would be covered in scary warning labels (much more than it is now).
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [June 6, 2012, 9:38pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/7 "2012-06-06T21:38:11Z")
> [@Washoe](#):
>
> I’ve been told several times that straight bleach will pit stainless steel. Any truth to this? I’ve tried it on scrap metal pieces and it didn’t seem to do a damn thing.
Probably, eventually it will pit any metal. But I’ve cleaned plenty of stainless steel with bleach without problems. I don’t know what would happen if you kept bleach in a SS container.
I’m terrible at chemistry, but I’d assume chlorine would combine with bases to form salts. And those salts are probably water soluable and get washed away in the rinse. Considering how long people have been using chlorine bleach to whiten clothes, I’d be surprised if this represents a major health hazard for common usage.
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### Author:  [@Washoe](https://boards.straightdope.com/u/Washoe)
#### Post date: [June 6, 2012, 9:50pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/8 "2012-06-06T21:50:59Z")
Yeah, that’s what I thought. I took retard chemistry (the expository non-calculus based course for nursing students) and the text said that the only metal that dissolves in base is aluminum. And bleach is _base_, not acid, right?
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### Author:  [@congodwarf](https://boards.straightdope.com/u/congodwarf)
#### Post date: [June 6, 2012, 9:50pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/9 "2012-06-06T21:50:59Z")
I’ve been told by many fishy people to clean my fish tank parts with bleach and then let them sit for a few days because the bleach will be completely gone when it’s done evaporating, rendering the items safe to put back in the fish tank.
The only time I ever killed any fish by cleaning was when I was inexperienced and stupid and I cleaned out everything, completely at the same time, with soap (now I do it in stages - clean decorations one day, change water 2 days later, change filter 2 days later - and I only use bleach).
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### Author:  [@congodwarf](https://boards.straightdope.com/u/congodwarf)
#### Post date: [June 6, 2012, 9:52pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/10 "2012-06-06T21:52:03Z")
> [@Washoe](#):
>
> Yeah, that’s what I thought. I took retard chemistry (the expository non-calculus based course for nursing students) and the text said that the only metal that dissolves in base is aluminum. And bleach is _base_, not acid, right?
Yes, bleach is a base.
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### Author:  [@VOW](https://boards.straightdope.com/u/VOW)
#### Post date: [June 6, 2012, 9:58pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/11 "2012-06-06T21:58:29Z")
As long as you stay away from the HYPER bleach solutions for cleaning (X-14 and the like), household bleach is relatively safe. It will dry out your skin if you clean bare-handed, and you can destroy any clothing you are wearing while in your cleaning frenzy. But as a disinfectant, a water purifier, and the fact it is damned cheap, you really can’t find a better product.
Any residue should be wiped up immediately with a water-dampened paper towel, and thrown away. You wouldn’t want the cat (or the baby!) to lick it up.
~VOW
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### Author:  [@Washoe](https://boards.straightdope.com/u/Washoe)
#### Post date: [June 6, 2012, 9:58pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/12 "2012-06-06T21:58:38Z")
No, wait—I’m wrong. Dissolve sodium hypochlorite in water and you get hypochlorous _acid_, right? So maybe it will dissolve metal if it’s strong enough and left in contact for a sufficient period of time. Amazing that I got an A in that course (just barely).
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### Author:  [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)
#### Post date: [June 6, 2012, 10:08pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/13 "2012-06-06T22:08:41Z")
Bleach is fine as long as used as the instructions say, but don’t underestimate it. It is a potent oxidant. As it evaporates, it loses oxygen and you get sodium chloride. What hazardous residues are left may by organic chlorides, but this is not going to be in hazardous concentrations. Wearing gloves is a good idea.
> [@Kevbo](#):
>
> It can and is used in many cases to chlorinate drinking water. Larger systems will use chlorine gas, but many smaller systems use Sodium Hypochlorite solution…bleach.
Guess what happens when you dissolve chlorine gas in water?
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### Author:  [@Washoe](https://boards.straightdope.com/u/Washoe)
#### Post date: [June 6, 2012, 10:30pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/14 "2012-06-06T22:30:41Z")
> [@WarmNPrickly](#):
>
> Guess what happens when you dissolve chlorine gas in water?
Uhhh…muriatic acid and hydroxyl anions? 😕
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### Author:  [@Waterman](https://boards.straightdope.com/u/Waterman)
#### Post date: [June 6, 2012, 10:34pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/15 "2012-06-06T22:34:13Z")
> [@WarmNPrickly](#):
>
> Bleach is fine as long as used as the instructions say, but don’t underestimate it. It is a potent oxidant. As it evaporates, it loses oxygen and you get sodium chloride. What hazardous residues are left may by organic chlorides, but this is not going to be in hazardous concentrations. Wearing gloves is a good idea.
>
> Guess what happens when you dissolve chlorine gas in water?
What you get is an appreciable concentration of hypochlorous acid (HOCl) in a saturated aqueous solution of chlorine. Specifically the equilibrium concentrations of chlorine in water at 25 degrees C are 0.061 moles/liter as Cl2(aq) and 0.030 moles/liter as HOCl.
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### Author:  [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)
#### Post date: [June 6, 2012, 10:37pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/16 "2012-06-06T22:37:14Z")
> [@WarmNPrickly](#):
>
> …
>
> Guess what happens when you dissolve chlorine gas in water?
Your mom?
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### Author:  [@Washoe](https://boards.straightdope.com/u/Washoe)
#### Post date: [June 6, 2012, 10:41pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/17 "2012-06-06T22:41:36Z")
> [@Waterman](#):
>
> What you get is an appreciable concentration of hypochlorous acid (HOCl) in a saturated aqueous solution of chlorine. Specifically the equilibrium concentrations of chlorine in water at 25 degrees C are 0.061 moles/liter as Cl2(aq) and 0.030 moles/liter as HOCl.
My professor musta been HIGH when he gave me that A… ☹
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### Author:  [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)
#### Post date: [June 6, 2012, 10:45pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/18 "2012-06-06T22:45:53Z")
> [@Waterman](#):
>
> What you get is an appreciable concentration of hypochlorous acid (HOCl) in a saturated aqueous solution of chlorine. Specifically the equilibrium concentrations of chlorine in water at 25 degrees C are 0.061 moles/liter as Cl2(aq) and 0.030 moles/liter as HOCl.
It depends heavily on pH,but unless you are at a pH below 3, it is predominantly hpochlorous acid,which is the acid of sodium hypochlorite. I don’t know where your numbers are coming from. I’ll see if I can dig up mine, but your numbers aren’t consistent with what I remember.
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### Author:  [@Waterman](https://boards.straightdope.com/u/Waterman)
#### Post date: [June 6, 2012, 10:58pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/19 "2012-06-06T22:58:06Z")
Bleach (NaOCl) solutions loses its strength by two decomposition pathways. Under normal conditions, the dominant pathway leads to the formation of chlorate and chloride ions, and a slower second reaction leads to oxygen and chloride ion formation.
I’d write out the reactions but I can’t get superscripts and subscripts to work in the reply box.
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### Author:  [@Inner\_Stickler](https://boards.straightdope.com/u/Inner_Stickler)
#### Post date: [June 6, 2012, 11:01pm UTC](https://boards.straightdope.com/t/how-safe-is-bleach-to-use/624301/20 "2012-06-06T23:01:00Z")
[noparse][sup]2[/sup][/noparse] gets you [sup]2[/sup]
[noparse][sub]2[/sub][/noparse] gets you [sub]2[/sub]
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