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The simplest way to prepare chlorate involves thermal decomposition of hypochlorite, where it is simply boiled in water solution. Following reactions takes place, depending on pH:
2HClO + ClO- ==> ClO3- + 2H+ + 2Cl-
2HClO + ClO- + 2OH- ==> ClO3- + 2Cl- + 2H2O
There are many sources of hypochlorite, most usual is bleach, which usually contains <5% sodium hypochlorite. Solid sodium or calcium hypochlorites can be found in pool shops.
Further I will describe how to convert and extract potassium chlorate from bleach (5% solution of sodium hypochlorite).
| Materials: |
| Bleach (Sodium hypochlorite solution) |
| Potassium chloride (KCl) (or KCl containing salt substitute) |
Boil down 1 litre of bleach to approximately 140 ml, preferably in a glass beaker (Note, beaker will become dull!..). Stainless steel container could be used instead. Chill obtained solution to room temperature. If solid precipitates, it should be filtered and throwed away, that’s NaCl.
Add 17 g KCl into solution and bring it to boil, if some will remain undissolved you should add small portions of water and wait until everything dissolves. After, chill down solution to 0*C and vacuum filter, wash filtrate with small portion of cold water. If vacuum filtration is not available, transfer crystals on a piece of textile and press out as much liquid as possible. Obtained crystals can be dried or purified by recrystallization. To recrytalise, dissolve crystals in minimal amount of boiling water and chill to 0*C, filter as above.
I used 750ml bleach and extracted chlorate with salt substitute "Seltin" which contained 60% KCl, the yield of chlorate is 11 g.
Solid hypochlorite as Ca(ClO)2 can be converted the same way but first, it have to be dissolved in water to form ~30% solution1 [NOTE 08.05.05: not tested by me, this procedure seems to give bad yields].
[NOTE 22.07.05: Seems like thermal decompositon of a solution of commercial Ca(ClO)2 produces majorly oxygen. This suppose to happen in presence of catalysts as oxides of silver, cobalt, nickel, copper, iron or barium.. To be able to decompose hypochlorite to chlorate one have to identify the present catalyst(s) and somehow deactivate it/them..]
Basically, amount of needed KCl can be calculated from equations above.
Instead of pure KCl one can use "salt substitute" which can contain up to 60% KCl. It can be found in most food stores together with usual table salt (on same shelf..)
If potassium chlorate does not form upon cooling, this has to do most likely with following things:
a) Solution did not cooled completely to 0*C
b) You have boiled away to small amount of liquid, 1 litre should be boiled down to 140 ml
c) Your bleach contain to small amount of hypochlorite, check the label that it contains something like "<5% sodium hypochlorite" and not "<5% free chlorine"
d) Something is wrong with your KCl
1. http://huizen.dds.nl/~wfvisser/EN/chlorate_EN.html
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