Tuesday, July 17, 2012

How to make ammonium perchlorate : electrolysis

As I told you earlier, ammonium perchlorate (AP) is not available in all countries.
Here is a way to make it.

First, AP is made by electrolysis of a solution of sodium chloride (table salt or NaCl).
Electrolysis is made by plunging 2 electrodes (an anode and a cathode) in an electrically conductive solution called electrolyte and plugging these electrodes to a power supply.

The electrolysis of NaCl results in the production of chlorine (Cl) and soda (NaOH). After a number of complex chemical and electrochemical reactions occurs as the chlorine dissolve in the solution.

This will yield sodium chlorate (NaClO3) if you have choose to use sodium chloride in your electrolyte, you can use potassium chloride (KCl) and you will have potassium chlorate (KClO3).
But KClO3 solubility is very low compared to NaClO3 so that it will precipitate out of the solution.
Not good for making perchlorate as the chlorate needs to be in solution in order to be electrolyzed in perchlorate.

NEVER USE AMMONIUM CHLORIDE (NH4Cl) in the electrolyte because the resulting salt ammonium chlorate is very instable though very dangerous.

Now that the sodium chlorate is made, let run the electrolysis. The chlorate will be electrolyzed to the corresponding perchlorate.

Once the electrolysis done, there is sodium perchlorate in the electrolyte. To obtain ammonium or potassium perchlorate, we will use what is called a double decomposition.
Introduce, either ammonium or potassium chloride in the solution and the corresponding salt will precipitate out as their solubility is very low compared to sodium perchlorate. To finish, extract the perchlorate and let it dry in the sun.

This post was the process of making the perchlorate, further post will cover the details like the electrode's materials (very important) and recycling the solution.

7 comments:

  1. How much ammonium would need to be introduced per oz of sodium perchlorate solution.

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    1. Thanks for your interest.
      To answer you, you would need a stoichiometric amount of ammonium, or in non-chemist terms for 1 g of sodium perchlorate, you add 0.5 g of ammonium chloride.

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  2. How would I extract the AP from the solution? I was thinking boiling could work or would that cause the AP to decompose.

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    1. Hello,
      Actually, you don't have to do this because one of the useful characteristics it has, besides its powerful oxidizing power, is that it is insoluble in water.
      So when you add ammonium chloride to your sodium perchlorate solution, AP will precipitate out of solution.
      You just have to filter out the AP and you can also reuse the solution for another batch.

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  3. Thanks for you help. Sorry to keep asking question I just have two more I need to ask , would I need to run the cell with the save current as I did to make the electrodes? How long does it need to run.

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    1. Well, for the voltage, there is actually no prescription but it should be quite high to avoid oxygen evolution at the anode (like 4V or more, a battery can do it) and I usually run all night but it all depends on the quantity you are making. The lower the quantity, the lower the time and vice-versa.

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