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Accidental Titration w/ Indicator

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Shaun

Wed May 30 2007, 11:43PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

So I was at work the other day, and we were getting ready to mop up at the end of the night. The mop bucket has 2 cleaners added, bleach and something called G.P. Fresh (?). After the bleach is added to the hot water, the GP Fresh, which is dark green, turns clear instantly upon being added, up to a very specific point after which it remains green.

I know bleach's NaOCl is a weak acid, and on further inspection of the label on the GP Fresh, I see "It's slightly acidic pH will not harm floors..." and on the ingredients, citric acid is present.

What I'm wondering is, what causes the color change? Could the dye just be naturally pH sensitive?

Chris

Wed May 30 2007, 11:53PM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

NaOCl is not an acid, as it has no H+. In fact typical bleach solutions contain a significant amount of sodium hydroxide left over from production. As a strong base, this likely caused the reaction. The dye could be an inadvertant pH indicator, or possibly the chemicals in the bleach just reacted with it regardless of pH, destroying the color.

ragnar

Thu May 31 2007, 12:00AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

I found most of the inks from my blue pens turn green, if you write on something absorbent and apply a drop of acid... =P

Shaun

Thu May 31 2007, 05:52AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Oh sorry, weak acid for NaOCl is a typo, i meant weak base.

Bored Chemist

Thu May 31 2007, 04:50PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

All the bottles of bleach I have seen (at least since I started reading that sort of thing) have warned that they shouldn't be mixed with other products. Does yours?

Shaun

Thu May 31 2007, 07:21PM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Well, yea, both bottles do say that, but my boss(es) are what you might call, well, chemically retarded. I saw no bubbles or foam forming (which I have seen with a mix of bleach and hand soap with bleach alternative), just the color change. I figure at the most it makes it clean worse by partially neutralizing the cleaning agents.

The possibility that the bleach simply destroys the dye makes a lot of sense to me now. That is what bleach is known for, right? Oxidizing away color?

sparky

Fri Jun 01 2007, 01:35AM

Registered Member #530 Joined: Sat Feb 17 2007, 07:56AM
Location: Victoria BC, Canada
Posts: 178

Mixing strong Acids with NaOCl based products is a BIG no no! Its a fast way to wind yourself up in the ER with a serious case of Chlorine gas poisoning! I once saw a nasty accident with Industrial bleach and liquid drain remover - 95% H2SO4 --- VERY violent reaction and lots and lots of Chlorine gas....

Shaun

Fri Jun 01 2007, 04:13AM

Registered Member #690 Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616

Believe me, I know where you're coming from. I had a few nice whiffs of Cl2 during a chlorate electrolysis process. As I said, no bubbles were formed upon mixing. I know this doesn't neccesarily mean no gas is forming (see aqueous NaOH + NH4NO3 solution), but if anyone would recognize the scent of chlorine, it would be me, and there was none. A small amount probably did form initially, but there was so much water and so little reagent, that the gas should have just gone into solution, as it is fairly soluble.

I do my best to stay safe, really, but acids and gases tend to make you rethink your methods...

Simon

Fri Jun 01 2007, 05:51AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Yes, bleach has a nasty habit of releasing chlorine gas (or worse) with a whole range of chemicals.

wrote ...

NaOCl is not an acid, as it has no H+.

On a technicality, an acid doesn't have to contain H+, depending on definition. The common high-school acid definition is centred on H+ (the Bronsted-Lowry definition, I think it is) but there are other kinds of acid.

FeCl3 (that etchant) is considered a kind of acid. Formally it is a Lewis acid. No H whatsoever.

Edit: Whoops! Thanks BC! Embarrassing... (I'm supposed to be a chem tutor, too...)

Bored Chemist

Fri Jun 01 2007, 04:56PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

That was a good point right up until you gave the wrong formula for Ferric chloride.

Surely the real point is why bother to mix the products?

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