chief
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HClO3 from Pb(ClO3)2 + H2SO4
Since I have a hard time recrystallizing NaClO3 from NaClO3/NaCl-solution (want to get rid of all chloride, but under the microscope NaClO3 gives
cubes, as well as NaCl, also polarized light does not help, since both are cubic) and don't know how much is left of NaCl in the ppt., I now have the
following idea:
==> solubility of Pb(ClO3)2, wikipedia: 0.037 gm/(100 g H2O)
(http://en.wikipedia.org/wiki/Solubility_table#L)
==> Now: ppt out the Pb(ClO3)2 (using Pb(NO3)2-solution, from the electrode-plating)
==> with dilute H2SO4 (10-20 %) ==> HClO3 + PbSO4 (insoluble)
The HClO3 then could be reacted with any carbonate (Na again, want NaClO3) for the chlorate ...
and the PbSO4 maybe carbonatized via Soda-boiling for another Pb(NO3)-batch ...
But: How dangerous would the Pb(ClO3)2 be ?? since at least _this_ link:
http://www.retrobibliothek.de/retrobib/seite.html?id=121766
states that
==> Ba(ClO3)2-crystals explode upon hitting,
==> and Ba-Pb-similarities are more than one, only that Pb might give even more dangerous compounds ...
[Edited on 5-10-2008 by chief]
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woelen
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I don't think these chlorates are that dangerous, as long as you do not hit them with a heavy sledge hammer. I have experience with Ba-chlorate and
bromate and they cannot be made to explode easily, without the presence of a reductor. Combined with a suitable reductor, such as sulphur it indeed
can easily be made to explode, but that is true for every anhydrous chlorate.
So, as long as you use due care during your experiments you should be safe. I would be worried more about the toxicity of the compounds involved. The
lead-salts are exceptionally toxic and if they are dissolved and bubbles of gas are produced, or if they are heated, then small amounts of Pb-salts
may go into the air, giving a serious poisoning risk.
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12AX7
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PbCl2 is insoluble.
I thought the chlorate was soluble?
HClO3 isn't too great, it decomposes into Cl2 and ClO2. It's a moderately strong acid (pKa = 1 or so IIRC).
Tim
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woelen
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Yes, Tim is right. I read over this question too fast. The proposed method is not suitable at all for separating chloride from chlorate. Why do you
want NaClO3? Making pure KClO3 is easy, the solubility of KCl and KClO3 differs a lot, but only when the liquid is cold. So, you dissolve as much of
KCl as possible in the solution while it is hot and on cooling down almost pure KClO3 crystallized. Dissolving this in as little as possible boiling
hot water and slowly letting cool down makes the crystals really pure, any remaining KCl and NaCl will remain in solution after this second
crystallization.
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chief
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I want to try NaMnO4, therefor NaClO3. From the NaMnO4 I could go to some of the other manganates ... ; besides: I was really false about the
solubility of PbCl2, assumed it were soluble adn didn't look it up.
I made some crystallization-experiments on the polarizing microscope: All the way cubic cubes crystallize, and finally, at last, some birefringent
stuff. Now I read somewhere that from conc. solutions (with NaCl) the NaClO3 may crystallize tetragonal ... so I still don't know if most of the
NaClO3 is just cubic, or not there at all.
The initial difficulty was that I started the electrolysis with conc. electrolyte, so there was way too much chloride still presentwhen I wanted to
separate the chlorate ..
So I boiled it down, washed th ppt, boiled down again etc. ...
Since I want to go for the manganate I just want to get rid of the chloride; the crystallizing salt is already an oxidizer, as I checked, so there is
definately chlorate in it ...
I now tried to use the Pb(NO3)-ppt. to look under the microscope, if the chloride could look different from the chlorate, but this also does not work.
[Edited on 5-10-2008 by chief]
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12AX7
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How about this. Crystallize it all, then wash with hot water. Most of the sodium chlorate will dissolve rapidly, leaving the chloride. Repeat as
needed until concentrated enough to precipitate pure chlorate on cooling (the chlorate has a wide range of solubility over temperature, whereas the
chloride is almost constant).
Tim
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dann2
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There is a mutual solubility graph of Sodium Chloride/Chlorate at the link below, if that is any help.
It will not much use to you if you do not know how much Na Chloride and Chlorate you have in the solution to start with.
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
Dann2
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Taoiseach
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You can boil NaCl out of a NaCl/NaClO3 solution. I have done this sucessfully to purify NaClO3. The only limitation is you need to know exactly how
much NaClO3 there is in your solution. Calculate how much water is needed to dissolve all chlorate at 100°C and boil down your solution to this
volume. NaCl will precipate first due to lower solubility @100°C. As soon as the precipation begins, heavy bumping starts and the solution will be
spilled everywhere unless you use magnetic stirring. If you dont have a magnetic stirrer, use a large Erlenmeyer and swirl it over a gas burner. Once
final volume is reached, dump it into a large coffee filter. The resulting solution can be boiled down to 50% of its initial volume. Upon cooling,
crystals of relatively pure NaClO3 will form.
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