Sodium hypochlorite salt from bleach, is it possible?

[MarcoP]

Hi all,
I'm looking into the HCl/Cl method and as everyone says one of the big cons is the high volume of solution we end up with. So I start looking and I was able to get 5 liters of 20-24% bleach for just few euros.

While keeping my research active I've found out that NaClO will keep releasing Oxygen leaving me with a more and more weak bleach. This also explain why, even if kept on a cool and dark place, I find the 5L container under pressure which also worries me, some advise on this would be also appreciated.

After searching the forums for a couple of days I've found no hints on concentrating the bleach or getting the salt out, so I'm guessing its not possible, otherwise it would have been already discussed and used.
I would like to make sure if there is a way to get pure sodium hypochlorite salt out of the bleach, or stop it's decomposition.

Thank you in advance.

 

[solar_plasma]

The process is limited by the solubility of chlorine. It needs only some ml of 3% bleach and some 100ml HCl are saturated with chlorine. Your 20% bleach should be fine. If not, you can still dillute it 1:1.

 

[Geo]

Off the shelf bleach in the US is in the 4%-8% range sodium hypochlorite depending on brand. Follow storage instructions on the container and it should have a shelf life long enough to be able to use it all. Salt is produced in the processes we use but because NaCl is soluble in water, it can be completely wash out with water (relatively speaking). You may consider diluting your 20% before using.

 

[rickbb]

Remember that it is the free chlorine acting as an oxidizer that dissolves the gold. The action of the bleach mixed with HCL releases the chlorine into solution.

You only need a little bleach for this, using a concentration as high as 20% will make a lot of chlorine, more than you may need.

As others have said dilute it to use, letting it "weaken" over time should not be an issue as using a small amount of 3% to 5% bleach works quite well.

 

[Barren Realms 007]

You can also use sodium hypochlorite in granular form used for pools.

 

[MarcoP]

Thanks a lot for all your suggestions, I'll dilute it before using it.

I was also asking if it was possible to get the salt back not only to make my own solution when needed thus avoiding decomposition, so wasting it, but also because the guy where I bought it asked me if it was possible to know the real concentration of the solution as sometimes he thinks his supplier cheated him. From what I understood he may have received an old stock bleach.

 

[Geo]

When you mix the bleach with acid, the chlorine is liberated as a gas and is vented to the atmosphere. There's no way that I have ever heard of to reconstitute the bleach as it's much easier to obtain more. You can generate chlorine gas from salt (NaCl) using hot sulfuric acid. As far as finding the concentration, you can do a specific gravity test i suppose. You would have to know the specific gravity of the new, unused chemical to start with.

 

[g_axelsson]

I had never heard about generating chlorine from sulfuric acid before, but I found this reference. You need an oxidizer too, the sulfuric and salt is only used to form hydrochloric acid that is later oxidized into water and chlorine.

http://chem-guide.blogspot.se/2010/04/preparation-of-halogen.html

Göran

 

[Geo]

I had never heard about generating chlorine from sulfuric acid before, but I found this reference. You need an oxidizer too, the sulfuric and salt is only used to form hydrochloric acid that is later oxidized into water and chlorine.

http://chem-guide.blogspot.se/2010/04/preparation-of-halogen.html

Göran

Technically speaking, the sulfuric acid is the catalyst because it is not consumed in the reaction. It's just used to break the chemical bonds between the sodium and chlorine. I've followed the reaction a couple of times through study and even watched a couple of videos depicting the reaction and final product. I was considering using it to dissolve gold without adding any extra chemicals other than hcl and chlorine. I finally decided it would be more trouble than it was worth but it's better to have the knowledge and not need it than to need it and not have it.

As an aside, you can make sulfuric acid by roasting sulfites (pyrite) and bubbling the off gasses through water.

 

[g_axelsson]

Technically speaking, the sulfuric acid is the catalyst because it is not consumed in the reaction. It's just used to break the chemical bonds between the sodium and chlorine.

That doesn't sound correct, can you give an equation?

In the equations on the page I linked to the sulfuric acid is used up, turned into NaHSO₄.

Göran

 

[Geo]

Goran, I will have to concede because I can't find my text notes on it. From memory, the byproduct was sodium sulfate. The reason I said it was not consumed may be because an excess of sulfuric acid was used. Most of the worlds sodium sulfate is a byproduct from the production of hcl by reacting NaCl with sulfuric acid. Bubbling the gas through water makes hcl but adding an oxidizer makes chlorine gas. It seems the two processes is related though. Im glad there are real chemist here to keep me straight. :lol:

 

[g_axelsson]

Im glad there are real chemist here to keep me straight. :lol:

Sorry, I think you got me confused with someone else, I'm a physicist. 8)

Göran