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Author: Subject: Chlorate the other way
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[*] posted on 17-4-2009 at 04:59
Chlorate the other way

Supposed I have enough conc. HCl, as well MnO2 and NaOH OR Ba(OH)2 :
Could I just make a hot solution of hydroxide, bubble in the chlorine and ready ? Could be quicker than waiting for a tedious electrolysis to get finished ?

[Edited on 17-4-2009 by chief]
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[*] posted on 17-4-2009 at 05:12

You can make chlorate in this way if the solutions are hot, but the trouble is that only 1/6 of all chlorine ends up in chlorate, the other 5/6 end up in chloride. Isolating the chlorate from such dilute solutions is not easy, especially if you have the highly soluble chlorates of sodium or barium. This works better with KOH making KClO3.

With electrolysis you make chlorate (through the intermediate of hypochlorite) but there you continue with making chlorine as long as chloride is present. So, in electrolysis you finally use up all chloride, converting it to chlorate.

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[*] posted on 17-4-2009 at 05:45

If we knew what exactly the fire suppressants in chlorate weedkiller are, it might be possible to separate them by fractionation. . .
Thermal oxidation to NaClO4 produces 1/3 NaCl which is manageable.
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[*] posted on 17-4-2009 at 06:41

We do know that, the MSDS tells you. In the EU, where the products look to be going away in the next year or so, the main additive is NaCl.

In the US it is generally sodium metaborate, which has a solubility somewhat similar to sodium chlorate. Adding the correct amount of boric acid converts the metaborate to borax, which has a much lower solubility in cool and cold water and gives decent separation.

Calcium chlorate is also used, at the time it was accessible where I was living the additives varied greatly, it was a bag by bag decision on how to clean it up to get Na or K ClO3.

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[*] posted on 27-4-2009 at 13:03

In all brands of chlorate weedkiller that I've come across the sodium chlorate crystals are bigger than the fire suppressant crystals, so mechanical sieving gives pure sodium chlorate. Use the coarsest sieve possible, to ensure that it only retains chlorate. The weedkiller container will tell you what % chlorate it is. So then you weigh what you sieved out, work out how much chlorate is still left in the fire suppressant, and use KCl or KNO3 to precipitate the rest of the chlorate as KClO3 which has low solubility in cold water.
You can skip the sieving if all you want is KClO3, but I like to have both NaClO3 and KClO3.
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