Alternate synthesis of (Per)chlorates

[Respirator]

I have searched through the chemistry forum and couldn't find anything similar to a complete summary of routes to synthesis the chlorate or perchlorate ion and it's compounds.

I also found a large amount of info in the (per)chlorate thread and made my way through a few tens of its 135 pages. The information there is great BUT it takes up a vast chunk of room and can take over a week to read (for the average student computer user).

 

This thread is dedicated to discussing all methods of reaching the oxidizers - whether practical or theoretical.

I'll start:

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- Electrolysis of a chloride salt to give chlorate and later perchlorate,

Anion: Chlorate or Perchlorate

 

This is by far the most common method and involves runing an electric current trough a solution of a chloride salt. It is used commercially and discussed in many threads on this forum.

Practicality: Very high

Yield and quality: Depends on the manufacturers skill but can be pure while and yield can be very high.

 

- Bleach method - heating hypochlorite, which disproportionates into chloride and chlorate,

Anion: Chlorate only

 

This is a method featured in a certain Cookbook but is also popular on Youtube with surprisingly good quality results. Basically - heating bleach.

Practicality: Moderate, especially If you can't stand the stench of chlorine while your gallon of bleach is boiling.

Yield and quality: Usually a very small amount of chlorate per amount of bleach just because of chemistry - even if the user is proficient. High quality is hard to make but is possible.

 

- Chlorine + NaOH reaction - 8H2O +2Cl2 +4NaOH ==> 4NaClO3 + 9H2 .

Anion: Chlorate

 

A less pleasant method as it uses corrosive sodium hydroxide and highly toxic chlorine gas. Chloride can be generated through a HCl + manganese oxide or potassium (per)manganate generator. Reaction should be heated 45-50 C

Practicality: High

Yield and quality: A very high quality product if all NaOH has reacted.

 

- Calcium Hypochlorite method (suggested by taiwanluthiers)

Anion: Chlorate

 

A rare method but quite as simple as combining potassium sulfate and calcium hypochlorite in solution. Potassium chlorate precipitates out.

Practicality: Very high

Yield and quality: Usually high quality yield although not totally efficient, it certainly is more so than bleach.

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Any others - mention below and I can edit. I will also edit in advantages disadvantages and practicality once I get mere time on my hands.

 

REMEMBER - this thread is about how to make either of the two polyatomic ions mentioned above. Do not write of how to make potassium perchlorate from perchloric acid as the ClO4^- anion already exists. Also do not mention how to convert Na+ ==> K+ salts or similar.

 

Also remember that purely theoretical methods are also welcome and even encouraged.

Edited May 15, 2014 by Respirator

[taiwanluthiers]

Bleach method is mentioned in the anarchist cookbook, while it works it's terribly inefficient because you'll get maybe 50 grams of chlorate from a bottle of bleach. The chlorine + NaOH reaction already happens with electrolysis, after all it produces chlorine which in turn reacts with the NaOH (produced by the electrolysis reaction as well) to eventually form chlorate.

[Respirator]

Are you sure thre would be a similar Cl + NaOH reaction in electrolysis? Wouldn't it be something like:

2H2O + 2e- ==> H2 + 2OH-

 

Then Cl2 + H2O ==> HClO + H+ + Cl-

 

2HClO + ClO- +2OH- ==> ClO3- + 2Cl- + H2O, and the Na+ reacts with ClO3- to NaClO3

(I understand there are many different reactions in electrolysis so I could be wrong....)

I also wanted to make it separate because it is a viable method by itself i.e bubbling chlorine gas through a hot saturated solution of a hydroxide gives reasonable chlorate.

[taiwanluthiers]

Also there's the calcium hypochlorite method... although I've read it's really dangerous (noxious fumes and stuff, with limited yield)...

[Mumbles]

The chlorine + NaOH method is in essence just a more dangerous, but more concentrated version of the bleach method from a chemical standpoint. Basically what is happening is that you're initially producing bleach and NaCl. From there, the hypochlorite is decomposing eventually to chlorate and 2 more equivalents of NaCl. At best, that method can only be 25% efficient. That is a limitation of the chemistry itself. It might be possible to convert more than 25% of the NaOH into NaClO3, but that will be at the expense of excess chlorine to generate the necessary oxidizing equivalents.

 

Electrolysis basically operates on the same chemical principles, but regenerates the chlorine trapped as chloride in the cell.

[Respirator]

taiwanluthiers - I can only assume that you meant the calcium hypochlorite / potassium sulfate method which I included above. Or did you have something different in mind?

[GalFisk]

The calcium hypochlorite/potassium sulfate method is interesting in that sodium is not involved anywhere in the reaction. The potassium chlorate produced can also be thermally decomposed to perchlorate and chloride, so it's possible to get all the way to perch without using electrolysis. The synthesis is pretty straightforward and the equipment and starting chemicals cheap.

 

Utah Pyro have several documents on prepering chlorates and perchlorates:

Chlorates by electrolysis, from bleach, and from calcium hypochlorite: http://www.utahpyro.org/compositions/PreparingChlorates.pdf

Perchlorates from chlorates by electrolysis, thermal decomposition and chemical oxidation: http://www.utahpyro.org/compositions/PreparingPerchlorates.pdf

Sodium perchlorate by electrolys in more detail, including how to plate PbO2 onto graphite for anodes: http://www.utahpyro.org/compositions/HowToMakeSodiumPerchlorate.pdf

[Differential]

For the K2SO4 and Ca(OCl)2 method, would this be the balanced reaction?

 

3 Ca(OCl)2 + 3K2SO4 --> 4 KCl + 2 KClO3 + 3 CaSO4

 

I think both the potassium chlorate and calcium sulfate would precipitate.

 

Just a guess, but sodium sulfate might work better (if it works at all), since sodium chlorate is about 3 times more soluble than sodium chloride.

 

http://en.wikipedia.org/wiki/Solubility_table

Edited December 15, 2014 by Differential

[Mumbles]

If I understand it, that is the correct overall formula but is not indicative of the chemistry going on. It's probably easier to think of it in two parts.

 

K2SO4 + Ca(OCl)2 ---> 2 KOCl + CaSO4(ppct)

 

From here the calcium sulfate and all the calcium hydroxide also present in pool chlorinator can be filtered off.

 

From there, the familiar thermolysis of hypochlorite can be done, where in the chlorate can be isolated by crystallization.

 

3 KOCl ---> KClO3 + 2KCl

 

This is still just a crude, ugly method that isn't really viable for actual pyro. Electrolysis is becoming accessible enough that this method is really only applicable to 12 year old kids without the intellectual means to handle real chemistry.

[GalFisk]

I think it could still be useful as a one-off, or as a first step in familiarizing oneself with (per)chlorate synthesis and purification. Or as a historical curiosity, since similar methods were used industrially before electrolysis became more practical.

 

I'm inclined to try it for the above reasons. I don't really need any chlorate or more perchlorate for several years, but it will be nice to know that I'm able to make it, and a bit of what the synthesis and purification entails - without spending time and money building electrolysis equipment.

 

When the day eventually arrives that I actually have a need to manufacture (per)chlorates for pyro use, I expect that I too will go the electrolysis route, and that having done parts of the synthesis already will then enable me to make more educated choices when it comes to equipment and procedures.