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[*] posted on 28-3-2008 at 05:53
NaOCl


I've had a browse and I can't find any reference on purifying Sodium hypochlorite from common bleach.

Does one exist?
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[*] posted on 28-3-2008 at 05:59


you`r probably better off making your own to be honest, you can get a good 10%+ soln of it quite easily, although anything beyond 12% IIRC isn`t possible without special storage conditions.



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[*] posted on 28-3-2008 at 06:36


Actually, according to Brauer (see attached) crystalline NaOCl.5H20 is isolable, and its solubility in water is just under 30 g/100 ml which sounds awfully like 29%+ to me. Neither very stable, of course.

And YT is right, you can't get there from Clorox. You get there from Cl2 and NaOH and water.



[Edited on 28-3-2008 by Sauron]

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[*] posted on 28-3-2008 at 06:45


Sauron, good to see you here again!

I would want to add one more thing. When you make bleach by bubbling Cl2 through a solution of NaOH, then do this slowly, or use adequate cooling. Otherwise you get too much disproportionation of your hypochlorite to chlorate and chloride.
Bubble through chlorine gas in a 10% solution of NaOH and continue, until the gas hardly is absorbed anymore.




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[*] posted on 28-3-2008 at 06:49


Quote:
Originally posted by woelen

Bubble through chlorine gas in a 10% solution of NaOH and continue, until the gas hardly is absorbed anymore.


100%, I do mine in a 2 chamber reaction and use the White paper test to spot for Cl2, don`t rely on smell, as Bleach and Cl2 smell the same to me and may also do for others, the white paper test is good.




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[*] posted on 28-3-2008 at 07:24


No, you need to leave a slight excess of NaOH in the bleach, if you add chlorine to NaOH until all NaOH has reacted the NaOCl will very rapidly disproportionate into NaClO3 and NaCl in the cold.
The excess chlorine acts like slight acidification, and NaOCl is only stable in very basic solutions.

In the manufacture of bleach, it is extremely important that at no place in the reactor there is an excess of chlorine.

The extent of chlorine absorption is generally monitored in the lab by periodically weighing the NaOH solution until ca. 90% of the calculated weight of Cl2 has been absorbed.




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[*] posted on 28-3-2008 at 10:40


That's interesting Sauron. I always thought NaOCl was not able to be isolated (in solid form) under standard conditions which is different from other hypochlorites.



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[*] posted on 28-3-2008 at 14:34


Very good info, garage chemist. Good that you wrote this. I really did not know that and I have done it twice, with slight excess of chlorine (when absorbtion becomes slow). Probably I have not noticed it, because I used it up directly after making it.



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[*] posted on 28-3-2008 at 21:35
NaOCl


I understand that NaOCl in solid form is an extremely unstable high explosive.
Garage Chemist, you mentioned weighing the flask containing the NaOCl to
determine how much Cl is absorbed. That appears to be a standard procedure
when making the 15% NaOCl used in the Raschig process for converting ammonia to
hydrazine.

Good point and excellent post, BTW !




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[*] posted on 29-3-2008 at 00:52


That`s interesting to note for next time, Thanks.
it would also go a long way to explain why I get a "Hiss" and a very strong off gassing of Cl2 when ever I open the bottle, even though all my chems are stored ~16c. this is even Better in a way because I can use less Cl2 making chems and use more NaOH (cheaper).
do anyone know if there is a Indicator that can be used to read the PH?
I only have Universal indicator testing papers, and as you know they all just get bleached white, so ideally it has to be something that remains unaffected by any bleaching action for a least a few seconds.

although I`v never had a problem with it not working in any of my experiments or synths, it will be nice to have a Purer product for the same effort.

Cheers :)



[Edited on 29-3-2008 by YT2095]




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[*] posted on 29-3-2008 at 04:31


"I only have Universal indicator testing papers, and as you know they all just get bleached white, so ideally it has to be something that remains unaffected by any bleaching action for a least a few seconds."

That's interesting. I have used those on 10% pool bleach before and I get a rather interesting effect. It forms a basic colored spot with an "acidic" ring around it. It takes a few seconds for it to start bleaching the color.




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[*] posted on 29-3-2008 at 07:34


YT, you can use universal indicator strips if you boil a small aliquot in a testtube, as it will expel any remaining chlorine, and decompose hypochlorite leaving an unbleaching solution.

[Edited on 29-3-2008 by The_Davster]




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[*] posted on 29-3-2008 at 08:05


Splendid Idea, I just tried exactly that and mine tests as Neutral, so certainly Not basic and that would probably explain the excess gassing I get when I open the bottle.
I`v added about 200mg of NaOH prills to this soln now, and hopefully it will help stabilize it until I get around to making a new batch.

Then it looks like some Serious Toilet Cleaning time :D




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