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Making Lye from Salt

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PhillipJ

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Here is the way they make lye. Probably bleach too? Called Chloralkali process.

The membrane in modern cells is a material called "Nafion" by Dupont. $150 for 3 sq. dm.

I figure one can be made with a glass meatloaf bowl or similar item. Thinking that a large clay pottery vessel could be the the membrane divider. That pottery vessel would be the part of the cell that holds the manufactured lye and steel cathode. A graphile anode might work in the salt bath, in place of titanium. DC Volts/amps would have to be experimented with to see what works best. Varying the distance of anode to cathode could control that. It would have to be done outside, or under a fume hood because of the chlorine gas that comes off. If it works, it could be enlarged to a plastic tub. When I get time, I'll try it. The clay cell works on precious metal refining. Might work for lye too?

Here's the hows & whys.

Membrane Cell

Basic membrane cell used in the electrolysis of brine.
The most common chloralkali process involves the electrolysis of aqueous sodium chloride (a brine) in a membrane cell.

Saturated brine is passed into the first chamber of the cell where the chloride ions are oxidized at the anode to chlorine:

2Cl- ? Cl2 + 2e-
At the cathode hydrogen in the water is reduced to hydrogen gas, releasing hydroxide ions into the solution:

2H2O + 2e- ? H2 + 2OH-
The non-permeable ion exchange membrane at the center of the cell allows the sodium ions (Na+) to pass to the second chamber where they react with the hydroxide ions to produce caustic soda (NaOH). The overall reaction for the electrolysis of brine is thus:

2NaCl + 2H2O ? Cl2 + H2 + 2NaOH
A membrane cell is used to prevent the reaction between the chlorine and hydroxide ions. If this reaction were to occur the chlorine would be disproportionated to form chlorine and hypochlorite ions:

Cl2 + 2OH- ? Cl- + ClO- + H2O
At higher temperatures, 333K, chlorate can be formed:

3Cl2 + 6OH- ? 5Cl- + ClO3- + H2O
Because of the corrosive nature of the chlorine produced, the anode has to be made from an unreactive metal such as titanium, whereas the cathode can be made from steel.

In the membrane cell, the anode and cathode are separated by an ion-permeable membrane. Saturated brine is fed to the compartment with the anode (the anolyte). A DC current is passed through the cell and the NaCl splits into its constituent components. The membrane passes Na+ ions to the cathode compartment (catholyte), where it forms sodium hydroxide in solution. The chloride ions are oxidised to chlorine gas at the anode, which is collected, purified and stored. Hydrogen gas and Hydroxide ions are formed at the cathode.


Diaphragm Cell
In the diaphragm cell process, there are two compartments separated by a permeable diaphragm, often made of asbestos fibers. Brine is introduced into the anode compartment and flows into the cathode compartment. Similarly to the Membrane Cell, chloride ions are oxidized at the anode to produce chlorine, and at the cathode, water is split into caustic soda and hydrogen. The diaphragm prevents the reaction of the caustic soda with the chlorine. A diluted caustic brine leaves the cell. The caustic soda must usually be concentrated to 50% and the salt removed. This is done using an evaporative process with about three tonnes of steam per tonne of caustic soda. The salt separated from the caustic brine can be used to saturate diluted brine. The chlorine contains oxygen and must often be purified by liquefaction and evaporation.
 

Soapmaker Man

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Thanks, 8) that sounds like a lot of work! :shock: I think as long as I can still by in bulk 50# bags for about 70 cents per pound, that is the way I'll go for sure. :lol: I want consistent results and am in doubt weather I could get this if I could figure out this process. I better stick to making soap and soap making tools!!!

Paul.... :wink:
 
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My brain hurts! I was never a big fan of chemistry. I think I will just buy it from the store LMAO!
 

PhillipJ

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It would be a lot of work. And most likely not even be cost wise. Unless it was set up to be mass produced.

For me it would be something to try, just for kicks.

Where are you folks getting the lye at such a good price?
 

Soapmaker Man

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I buy from a chemical supply store too locally. I bought 100 pounds before leaving Florida for 60 cents per pound! Online AAA Chemicals ( http://www.aaa-chemicals.com/ ) is a decently priced place to buy in bulk. I hear they are great shippers and fast.

Paul.... :wink:
 
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