21 Mar 2004, 22:50, JIM HOLSONBACK (1:123/140), wrote to ALL:

Hi JIM.

 JH> Hello, ALL.  I'm hoping this question is interesting, and BIR, we 
 JH> have at least one Chemistry major who at least lurks here.

Not me for sure, but lack of knowledge never stops me from commenting... :-))

 JH> While recently involved in cleaning up, painting and etc. on this
 JH> house in FL for selling it, I've become interested in learning 
 JH> more about the chemistry of bleach.

 JH> I think I've learned that bleach is manufactured by reacting a 
 JH> solution of lye (NaOH) with Chlorine (Cl2).  The product (bleach) is 
 JH> NaOCl. In the "household bleach" concentration, it is in
the range of 
 JH> 4 to 5% solution.

 JH> Although that is the way they say they make it at the Clorox 
 JH> website, 

If that's what they say at the Clorox website, I'll take their word for it.

 JH> I don't understand this recipe  - - seems like just reacting NaOH
 JH> solution with bubbling Cl2 gas would end up with extra hydrogen .
 JH> i.e.  NaOH + Cl = NaOcl +H

Likely incorrect, but 3NaOH + 2Cl = 2NaOCl + H2O (or something like that).

 JH> I've read that the "bleach" breaks down into NaCl (table salt) 
 JH> and Oxygen, and the the released Oxygen is what does all the 
 JH> "bleaching" work - -  Chlorine does none of this work.  I
also read - 
 JH> - extra NaOH is used in the manufacture, for stability, and to limit 
 JH> the pH to the 13 to 14 range.

 JH> My questions - -

 JH> 1.  If household bleach ends up being just table salt and oxygen, 
 JH>  why do we have the distinctive odor of Chlorine when we do a
"sniff" 
 JH> test?

It doesn't "end up" until all the 'activity' is finished.  Do
your white sheets smell like Cl when you sleep on them?  

 JH> 2.  Is the excess of NaOH from the manufacturing process the 
 JH> reason that it feels so "slippery" when we get a bit of
bleach on our 
 JH> hands and go to rinse it off?

Probably, as the NaOH _is_ very slippery.  Alkaline level pH is naturally
slippery.  A few drops of vinegar on your hands kills that high pH real
fast and gets rid of the slippery feel.

 JH> 3.  Could any excess  NaOH be a hygroscopic chemical - - that is, 
 JH> if there were to be any excess NaOH residue from previous bleaching
 JH> operations to kill mildew before repainting, could that be the 
 JH> reason that on the few "rainy days" we've had since the
underside of 
 JH> my patio deck was bleached down,  that the underside of some of the 
 JH> deck rafters has visible moisture accumulating on it??

I doubt it.  See below.

 JH> BTW, my painter-helper fellow used a "double strength" type of 
 JH> bleach solution - - about twice the strength of household bleach - as 
 JH> he gets from the swimming pool companies and they pitch this solution 
 JH> to the owners of RV's and etc. for purifying their water systems.  He 
 JH> sprayed it full-strength, low pressure, onto the bottom of the patio 
 JH> deck, and it is 1x6 T&G decking, with some cracks between the planks.  
 JH> We washed it all down later with 2500 psi pressure washer, but that 
 JH> could have driven any residue of the NaOH up into those cracks.  That 
 JH> is my theory for what I have seen - -- and the visible moisture 
 JH> condensation is occurring on the bottoms of only a small percent of 
 JH> those 3x6 or so patio deck rafters which support the 1x6 T&G wood 
 JH> deck.

Most likely, the 'wetness' of the boards causes them to cool quicker than
the ground surface, and the moisture from the warmer ground below the deck
is merely condensing on the nearest cooler surface beneath the deck.



     Good luck...  M.

--- Msged/386 TE 06 (pre)