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Author: Subject: Perchloric acid preparation
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thumbup.gif posted on 23-7-2003 at 07:32


I read that:
1)Chlorine dioxide dissolves in water without reacting unless
2)When the water is hot it disproportionates into chlorous and chloric acid or
3)On sunlight or UV the solution disproportionates into HCl and HClO4.
4)HClO2 decomposes into chlorate, chloride and ClO2
Also, only from a single (however hard have I tried to find out more) source I read of thic STRANGE reaction:
Cl2+NaNO3=>NaClO2+NOCl
I suggest it continues with:
5NaClO2+4HCl=>4ClO2+5NaCl+2H2O
8ClO2+4H2O(sunlight)=>3HCl+5HClO4
:o:)
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[*] posted on 16-10-2003 at 11:51


I found this out today and it just makes me agitated that I didn't figure it out on my own earlier. I remember back in chemistry lab when we would take saturated solutions of sodium chloride, run a little HCl gas through them and precipiate out the sodium chloride with the common ion effect. Today I came across.

NaClO4(aq) + HCl(aq) -----> NaCl (s) + HClO4(aq)

I could post more details if someone wants but appartently after filtering off the NaCl and heating to about 100C a 50% solution of HClO4 is acheived and the HCl volitizes off, the resulting solution gives no reaction with AgNO3 sounds insanely simple to me.
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[*] posted on 19-10-2003 at 06:07
Yes that works


A saturated NaClO4 solution with excess 35% HCl does work as indicated in my perchlorate book. But there may be trace NaClO4 in the perchloric acid and the book recommended vacuum distillation of the 72%HClO4 azetrope for purity. You do have to heat the acid to about 200C to drive off the excess HCl. Preferrably distill the 20%HCl azetrope for further sythesis to eleminate waste and recycle;)

[Edited on 10/19/2003 by chloric1]

[Edited on 10/19/2003 by chloric1]




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[*] posted on 19-10-2003 at 07:40
Extraction of perchloric acid with DCM


This might be interesting:
Quote:

quoted from U.S. patent 3,981,975
Anhydrous perchloric acid has been prepared by extraction of a perchloric acid-oleum solution with methylene chloride. See the article by P. H. Plesch et al., "Chemistry and Industry," September, 1971, pp. 1043 and 1044.

Has someone here access to this article?
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[*] posted on 19-10-2003 at 12:43


IIRC, that method was abandoned because the mixture of DCM and nearly anhydrous HClO4 was highly explosive.



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[*] posted on 3-11-2003 at 02:43


On the previous site of this topic there is the auto-oxidising -method of producing NaClO3:

3NaClO-> NaClO3+2NaCl

I have known this method for ages but now when I saw it I thought that I could ask if you know a good method of either removing the NaCl from the solution or extracting the NaClO3 from it. My methods are either dangerous or ineffective, for example causing the NaClO3 to decompose.
So, do you know any better ways?

[Edited on 3-11-2003 by the timeless]




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[*] posted on 3-11-2003 at 08:15


To seperate out the chlorate add some potassium chloride. The chlorate will precipitate out as the potassium salt. Solubility of potassium chlorate is 7.1g/100ml H2O and in boiling water it is 57g/100ml H2O. Compare to 79g/100ml cold H2O and 230g/100ml boling water for sodium chlorate. The potassium salt will crystalize out preferedly over the sodium chlorate the potassium chloride and the sodium chloride.
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[*] posted on 3-11-2003 at 10:34
Even easier


If you actually want the NaClO3 as opposed to KClO3, or youdon't have KCl on hand, just add lots more NaCl to a clean solution of NaCl/NaClO3 and water, and fractionally crystallize out the chlorate.

The excess of chloride ions reduce the solubility of sodium chlorate. Add salt to a warm (not boiling) solution and quickly chill it in the freezer, filter the crystals, re-warm it, rechill it (no need to add more salt) and repeat. Don't add somuch salt that you create a supersaturated solution at cold temps, but it will dissolve at warm temps,or you will contaminate your NaClO3 with precipitated NaCl.

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[*] posted on 17-3-2004 at 19:38
So, has anyone here made perchloric acid by the classical method?


Right now I have 5 lbs of KClO4 just sitting around, it's very pure and I have absolutely no use for it, my pyro days ended about 3 years ago, but there is no way in hell I'm just going to throw it away (although I could always eBay it). So I was thinking about perchloric acid.

Well, perchloric acid from KClO4 and H2SO4 requires high vacuum right? And oil bath I would assume, something like 70% H2SO4, actually, I've got all the conditions on hand but I was wondering if anyone has actually attempted to make it this way or has succeded, I've heard that even by this method, with an oil bath and careful heating it still explodes often, also, how much vacuum do I need if I decide to make an attempt?




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[*] posted on 2-5-2004 at 10:11


I decided that this might help, I've scanned in some interesting information regarding different methods of production of perchloric acid at my web site:

http://members.aol.com/bromicacid/perchlorate/perchlorate.ht...

So if you want some good information head on over. :)




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[*] posted on 9-10-2004 at 13:19


I attempted the classical method of perchloric acid production today. All my glassware was presoaked in concentrated HNO3 for a period of about 2 weeks then washed with hot distilled water to ensure cleanliness. All chemicals used were pure.

I took a 14/20 distillation apparatus and filled it with water and dropped a stir bar into it, and closed it. I applied vacuum the suction of my vacuum pump and it boiled rapidly at room temperature and pulled the liquid over into the receiver. Excelent.

Knowing that I had a powerful vacuum that would allow me to distill my perchloric well below atmospheric pressure and the 210 C where it decomposes redily I charged the 100 ml reaction flask with 12 g of KClO4 and 25 ml of 33% H2SO4. A stirbar was added and the apparatus connected together. It was held in a bath of water saturated with CaCl2 which gives it a high boiling point and the vacuum connection lead into an erlemyer full of a saturated NaOH solution and finally to the vacuum pump. Stirring was begun and the vacuum turned on.

Bad Move.

As you just read, I was using an aqueous solution of NaOH for the trap, as soon as it got under vacuum it foamed and frothed and boiled into the vacuum pump. Hummm... bad idea. Anyway, I replaced the liquid in the trap with a test tube containing solid NaOH which I placed in the erlemyer and put the tube to lead through that. One problem fixed.

After vacuum was applied this second time heating was begun and the mix kind of sat there. But I found out that the pipe I had leading into the solid NaOH touched the bottom too throughly and it had cut off the vacuum to the flask, found out too late is more like it. Because when I had found out the flask was already at 90 C and when I moved the tube by pulling from above the vacuum went though the vessel and flash boiled the perchlorate powder though the vessel and defeated the purpose of everything.

So I cleaned everything out with distilled water again and recharged the flask. Then heating was begun again. About 60 C the perchlorate powder at the bottom started to chaotically float from top to bottom. About 70 some bubbles came to the top and about 73 I got some distillate coming over. The flask was being magnetically stirred but I blame my air conditioner compressor. It had fits of low vacuum and high vacuum and it would occasionally almost pull over the reaction mixture. I turned down the hot plate to keep the mixture at about 80 C and distillate kept coming over. There was no problems at all. Well, except that my receiving flask had a crack developing from the chipped lip that it had. But suddenly the vacuum shot up again and caused the mix to boil fiercely and pulled over my KClO4 solid into the collection flask.

Worrying about the crack developing in the flask I shut down everything. I'm going to clean up in about 10 minutes.

The point of all this being. HClO4 distillation from a reaction mixture of H2SO4/KClO4 seems quite easy if you have a reliable vacuum source. I really want to try this again in the future, there was no strange reactivity in the reaction flask, it seemed incredibly tame compared to distilling HNO3 with the red vapors and everything. Just be sure to keep it below 150 C which is where HClO4 starts to decompose noticeably, use clean good reagents, and no organics at all! Soaking your glassware in 70% HNO3 seems like a good idea. Distilling anhydrous perchloric calls for greasing your glass joints with a KClO4/95% H2SO4 mixture but for the dihydrate (the azeotrope of about 70% HClO4) that distills over here I had no noticeable reactivity at all with teflon tape.




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[*] posted on 9-10-2004 at 13:44


chlorine peroxide will explode on contact with light. do not make it unless you have a death wish. if you breathe it in you will get pulmonary edema, also



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[*] posted on 9-10-2004 at 14:35


Where does Cl2O2 come into this?

The purpose of my post was to illustrate the relative safety of distilling HClO4 under reduced pressure. Significant decomposition only occurs above 150 C and I was distilling about 80 C which is well below the boiling point. People have distilled at atmospheric 210 C and lived to tell about it, it's just that decomposition occurs in upwards of 15% of the substance and there is a chance of explosion, usually chlorine dioxide is generated in this case, never heard of chlorine peroxide being formed.

However, what worried me more then the temperature or awkward byproducts was the inclusion of small pieces of organic matter in my reaction system, that would have probably given me a somewhat bad day.




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[*] posted on 10-10-2004 at 07:47


Quote:

I had no noticeable reactivity at all with teflon tape


Why should teflon not be compatible with perchloric acid?




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[*] posted on 10-10-2004 at 08:12


Although logically I didn't think it, there was a part of me that said perchloric acid would react with almost anything. Therefore it wasn't a surprize, just a sort of relief when the teflon tape didn't start bubbling and turning black, although I was worried about impurities.



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[*] posted on 11-10-2004 at 06:58


You could react ammonium perchlorate with nitrous acid to destroy the ammonium ion and leave perchloric acid behind.
Although the rising acidity may start to force the nitrous acid out of solution, this can be solved by slowly distilling N2O3 into the solution, which reversibly dissolves to form HNO2, which then reacts, as much is made as can be dissolved. In this way, I think a 100% yield can be achieved
The nitric/hydrochloric acid procedure in the PDF seems very nice, especially as you use 34 moles of NH4ClO4 and get 36 moles of HClO4 (with 99% yield, so still more than "possible";).
Another procedure is to take NH4ClO4 (the poor thing :D) and bubble chlorine through it. This will make HClO4, HCl and NCl3. On the bottom of the vessel there should be a catalyst that decomposes NCl3 preferably rapidly, but non-explosively. This will make chlorine, which will react with more NH4ClO4, and N2. When you're done with bubbling chlorine and decomposing NCl3, boil to remove the HCl. Though hazardous, I think this is a procedure that's at least as good as the others.




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[*] posted on 11-10-2004 at 07:15


Quote:
Where does Cl2O2 come into this?

Cl2O2 has nothing to do with this, but chlorine peroxide (ClO2) has everything to do with this, as it is incredibly unstable




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[*] posted on 11-10-2004 at 07:25


ClO2 is chlorine dioxide, Cl2O2 is chlorine peroxide.



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[*] posted on 12-10-2004 at 06:47


Also, aqua regia could be reacted with NH4ClO4 (this one is different from the oxidation mentioned in the PDF). The hydrochloric acid actually serves as a catalyst:

NH4ClO4 <=> NH4+ + ClO4-
HNO3 + 3HCl <=> Cl2 + NOCl + 2H2O
NH4+ + Cl2 <=> NH2Cl + HCl + H+
H+ + ClO4 <=> HClO4
NOCl <=> NO+ + Cl-
NH2Cl + NO+ <=> NONHCl + H+
NONHCl <=>NONCl- + H+
NONCl- => N2O + Cl-
2H+ + 2Cl- <=> 2HCl

Thus all your hydrochloric returns to you, so it functions as a catalyst.




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smile.gif posted on 21-11-2004 at 13:20
Perchloric acid preparation


I was wondering how I could hclo4 from naclo4 with out using hcl

If h2so4 works how could I react it safely with no explosions

and if it forms nahso4 will that decompose with heat to make a sulfur oxside
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[*] posted on 22-11-2004 at 00:55


Is it possible that chlorine dioxide be contained in a gel? You see, the supermarkets near my place sell a type of stuff that removes odour and dehumidifies the place. I have container of such stuff at home. It claims to contain ClO2, and besides the gel appears green in colour.

Is this possible? Isn't ClO2 dangerous?




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[*] posted on 22-11-2004 at 18:37


ClO2 is very unstable, and in concentration, explodes on contact with light.

You might have a hypochlorite perhaps? I have never smelled ClO2, but hypochlorites smell utterly foul, like chlorine bleach.




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[*] posted on 23-7-2005 at 14:35


I just came back from my first attempt to distill dilute perchloric acid. A scary experience.

In the boiling flask, there were placed 14g finely ground KClO4 and 5,6ml 96% H2SO4 diluted with 10ml water (more water than needed to make azeotropic HClO4). The joints of the apparatus were greased with conc. H2SO4.
It was distilled at atmospheric pressure first. About 7ml of distillate came over at 100°C, which was assumed to be water and was discarded. Then the temperature went up a lot, to about 180°C, where white fumes were produced in the distillation flask. However, I saw that noticeable evolution of incondensable gas started (presumably oxygen from decomposition of the HClO4), so I let it cool and connected my aspirator to the apparatus.
I turned on the water for the aspirator and heated the mixture slightly, more white fumes were produced which condensed nicely into the receiver. Then I took a look at the condenser- and saw a deposit of white material which could not possibly be KClO4 because the solution didnt splash.

I remembered that HClO4 forms a crystalline monohydrate. "If the condenser contains the monohydrate, what is the boiling flask going to contain?" I asked myself.

I pulled away the burner at once and backed away from the apparatus to let it cool down. I disconnected the aspirator hose very carefully and turned off the water. After cooling down, I very carefully dismantled the apparatus, wearing heavy gloves and face protection.
The liquid which wetted the stillhead from the inside fumed strongly in air, even though it was at room temperature! 72% HClO4 doesn't fume in air.

I let the apparatus air out until it didn't fume any more and thoroughly washed it.

However, I don't know what to do with the fuming boiling flask which contains anhydrous HClO4 with NaHSO4. Anhydrous HClO4 explodes from the heat of dilution when water is added.
I'm letting it stand open overnight, in hope that air humidity will dilute it safely until tomorrow.

I have no idea why the monohydrate and then anhydrous HClO4 was formed. Maybe the NaHSO4 retained the water?
Perhaps I should use an excess of KClO4?

BTW, the 3ml of distillate which came over in vacuum was HClO4 of quite a high concentration. It was not oily like the 72% HClO4, but it precipitated large amounts of KClO4 when a few drops of it were added to dilute KCl solution.

Now, what should I do? I want to make HClO4 from KClO4 without having to deal with the anhydrous acid. Are there really no procedures for this?
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[*] posted on 23-7-2005 at 16:03


Would Bromic's method (upthread) be feasible here?
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[*] posted on 23-7-2005 at 16:10


Garage chemist, "Brauer" has a good prep. for HClO4. Maybe by adding Anhydrouse Calcium chloride (CaCl2) you will be able to dilute your distilation flask content, for it will attract moisture from the air. You then can easily sepperate CaSO4 and solution of HCl, CaCl2 and Ca(ClO4)2. By adding KCl solution to the glasswool filtrate, you will be able to recover KClO4 by precipitation.
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