[bbro1997]

Sorry if I'm in the wrong forum, this is my first post. Please kindly redirect me if need be.

Anyway, I have built myself a decent Hoffman electrolysis apparatus out of PVC pipe to use for various experiments. I want to use electrolysis of a sodium chloride solution as a source of sodium hydroxide, but I cannot complete full electrolysis of the solution leaving me with a mixture of sodium hydroxide and sodium chloride.

I want to separate the NaOH from the NaCl, but I can't think of an easy way to do this. I would prefer to do it with common household materials. My current theory is pretty extensive:

First I would add CaCl2 (pool water hardener) to the solution to react with the NaOH to yield NaCl and Ca(OH)2. Calcium hydroxide has extremely low solubility, so I should see some precipitate in the solution, allowing me to dump the water and rinse the calcium hydroxide until it is nearly pure. Then, I'd mix it into a solution and add a solution of Na2CO3 (washing soda) to it to yield CaCO3 and NaOH. Since calcium carbonate is insoluble, it would precipitate, allowing me to dump and evaporate the remaining solution to give almost pure NaOH.

Anyway, that's my idea, but I'm not sure if there's a better way or not.

P.S. Are we allowed to discuss synthesis of hazardous materials like bromine? The rules only said not to discuss synthesis of drugs/explosives, but I just want to be sure.

[Hunter2]

Theoretically your wasy would work, but tom buy all these chemicals to obtain NaOh is more expensive as to buy directly sodium hydroxid or caustic soda solution.

Regarding Bromine: for what purpose you need it.  To make it is easy if you have source containing bromide.

[Archer]

Electrolysis of sodium chloride to prepare Sodium hydroxide is extremely hazardous as it produces chlorine gas as a bi-product.

How are you safely disposing of the chlorine gas?

Elemental bromine is commercially available from many chemical vendors. I would not attempt to make it as it is very toxic, corrosive and volatile.

[bbro1997]

As of right now I'm using the apparatus outdoors so the chlorine gas just diffuses into the atmosphere. However, the apparatus I made will also allow me to seal it off and build up chlorine gas inside of it until I need it (i.e. using it to isolate bromine from a solution of bromide salt).

Also just letting you know that I am aware of these dangers, and this is not something I am doing over the kitchen sink. Come time to do all of this, I'll be using a fume hood.

Regarding my question about bromine, it was just an example (though I would like to make some). My general question was if we're allowed to discuss synthesis of highly hazardous materials.

[Hunter2]

I think its allowed. Important what purpose is behind. Exception, Drugs, chemicals for warfare, explosives, etc.

I think nobody will say something how to optain Carbon acid ester by using phosgen. or made Isocyanates for making urethane.

[Archer]

I don't think this apparatus will work for bromine, liquid elemental bromine is very dense so it will not bubble up through the aparatus like chlorine gas.

Even in an open space Chlorine can be very hazardous so I would get yourself a fume hood as a matter of urgency.

[Hunter2]

Bromine will be collected in the solution. I think it can be easily extracted by using Tetra chlorine methane or others.

[curiouscat]

I want to separate the NaOH from the NaCl, but I can't think of an easy way to do this. I would prefer to do it with common household materials. My current theory is pretty extensive:

First I would add CaCl2 (pool water hardener) to the solution to react with the NaOH to yield NaCl and Ca(OH)2. Calcium hydroxide has extremely low solubility, so I should see some precipitate in the solution, allowing me to dump the water and rinse the calcium hydroxide until it is nearly pure. Then, I'd mix it into a solution and add a solution of Na2CO3 (washing soda) to it to yield CaCO3 and NaOH. Since calcium carbonate is insoluble, it would precipitate, allowing me to dump and evaporate the remaining solution to give almost pure NaOH.

Your strategy sounds silly to me.

You went: NaCl    (+electricity) NaOH  (+CaCl2) Ca(OH)2  (+Na2CO3)  NaOH 

Why not just buy some lime & start there? Or buy NaOH.
 

[bbro1997]

I'm not sure where I could pick up lime or NaOH locally. As for now my experiments will only use common household chemicals.

As for the bromine experiment, I was not going to directly electrolyze a solution of bromide salt. I was going to bubble chlorine gas into a solution of the bromide salt. This poses another problem however: getting the bromine out of the water. Would I be able to just boil out the bromine, since it boils before water?

[Borek]

NaOH is the basis of many drain cleaners.

[bbro1997]

Well in the meantime, I tried reacting CaCl2 (pool hardener) with Na2CO3 (washing soda) in fairly concentrated solutions, but nothing happens. The pool hardener is only 77% CaCl2 and 33% "other ingredients". Would this affect the results? I'm not seeing any CaCO3 precipitate like I should, so what's the deal?

[Borek]

The pool hardener is only 77% CaCl2 and 33% "other ingredients".

110% in total, interesting.

Would this affect the results?

Not knowing what the other ingredients are - it is enough that they keep the solution slightly acidic, and you will not see any precipitation.

[Archer]

As for the bromine experiment, I was not going to directly electrolyze a solution of bromide salt. I was going to bubble chlorine gas into a solution of the bromide salt.

What do you want elemental Bromine for? it is extremely dangerous to work with and has no practical uses outside of the chemistry lab.

If you don't know what you are doing when working with Chlorine and Bromine then you are highly likley to seriously injur yourself and others. 

[bbro1997]

Heh, my mistake, I meant 23% other ingredients. I was typing that up late last night.

As for my desire to isolate these potentially hazardous materials, well, it's just that - a desire. I'm a novice element collector who enjoys engaging in pretty much anything chemistry related, hazardous or not. However rest assured this isn't something that I'm blindly stumbling into. I have done thorough research and I am soon going to build a fume hood for myself to do this stuff in.