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Author: Subject: Perchloric acid preparation
plasma
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[*] posted on 20-5-2002 at 18:43
Perchloric acid preparation


Perchloric acid How can I make perchloric acid (HClO4) from hydrochloric acid (HCl) ?

I think the reaction would be like this:
HCl + H2SO4 -> HClO4 + 2H + S

Is this equation right (I don't really think so) ?
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[*] posted on 20-5-2002 at 18:43


Unfortunately, production of chlorine oxides is far more complex than that. It is possible to easily make perchloric acid from a perchlorate salt and sulfuric acid.



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[*] posted on 20-5-2002 at 18:44


You should see that this reaction is thermodynamically not right already.

You can also make HClO4 using a chlorate + H2SO4 and then heating it in the air. Partially oxidized to HClO4 then.
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[*] posted on 20-5-2002 at 18:44


What about this ?

36% 64% 32% 35% 33%
3NaOH + 3Cl2 -> NaClO3 + 2NaCl + 3HCl
warm

70% 30% 56% 44%
2NaClO3 + (COOH)2 -> 2NaHCO3 + 2ClO2
90-100 C

94% 6% 70% 24% 6%
4ClO2 + H2O -> 2HClO4 + Cl2 + O

Is there any easier way to get chlorine gas than by electrolysis ?
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[*] posted on 20-5-2002 at 18:45


Yes, there are much easier ways. Hydrochloric acid will react with various strong oxidizers to liberate chlorine gas. I recommend using either hydrogen peroxide, potassium permanganate, or manganese dioxide.

A good way to prepare sodium chlorate is the electrolysis of a hot aqueous solution of sodium chloride. Electrolysis of a cold solution of sodium chloride will yield sodium hypochlorite. Electrolysis of a cold solution of sodium chlorate will yield sodium perchlorate.

Chlorine gas will hydrolize to form hydrochloric acid and hypochlorous acid (HOCl).

Cl2 + H2O --> HCl + HOCl

Therefore, you could prepare an equamolar mixture of sodium chloride and sodium hypochlorite by bubbling chlorine gas through an aqueous solution of sodium hydroxide.

I believe the following reaction would occur:

2NaClO3 + (COOH)2 --> (COONa)2 + 2ClO2 + O2

DO NOT mix sodium chlorate with concentrated sulfuric acid, the reaction is explosive (just a general warning to any readers).

I believe the following reaction would occur:

2ClO2 + H2O --> HClO3 + HClO2

Both of those acids are unstable; I believe both of them have never been isolated in pure form.

8HClO2 --> 4H2O + 4ClO2 + 2Cl2O + O2
4HClO3 --> 2H2O + 4ClO2 + O2




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[*] posted on 20-5-2002 at 18:45


Thank you for your response
I will have to disagree with you :); chlorine dioxide mixed with hot water decomposes to perchloric acid and gives if chlorine and oxygen like this.

4ClO2 + H20 -> 2HClO4 + Cl2 + O

I got the theory confirmed by this site http://www.xrefer.com/entry.jsp?xrefid=486546&secid=.-
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[*] posted on 20-5-2002 at 18:46


Intriguing, thanks for that link!

I still think this reaction would occur:

2ClO2 + H2O --> HClO3 + HClO2

But, only in cold water. Clearly you are correct that ClO2 reacts with hot water to form HClO4 while liberating chlorine and oxygen gas; makes sense now that I think about it. This is what I think is occuring (I'll try to do some research on this tonight):

2ClO2 + H2O --> HClO3 + HClO2

(when the solution of HClO3 and HClO2 is heated, the HClO2, which is an unstable, powerful oxidizing agent, decomposes, oxidizing the HClO3 to HClO4)
2HClO3 + 2HClO2 --> 2HClO4 + H2O + Cl2 + O2

Therefore bubbling ClO2 through hot water should yield HClO4 while liberating chlorine and oxygen gas.

I'm thinking this is the equation for the reaction of moist (COOH)2 and NaClO3 at fairly high temperatures (90C-100C):

2NaClO3 + (COOH)2 --> Na2CO3 + 2ClO2 + H2O + CO2




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[*] posted on 20-5-2002 at 18:46


Oh, by the way, you can produce chlorates by heating an aqueous solution of hypochlorites.

3NaOCl ---(heat)---> NaClO3 + 2NaCl

Therefore bubbling Cl2 through a hot aqueous solution of NaOH would be a working method of preparing NaClO3.




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[*] posted on 20-5-2002 at 18:46


The hypochlorite method.
NaClO3 could be extracted by filtering, but I wonder; If 209g NaClO3 and 36g NaCl is mixed with 100ml water, does the NaCl solve at all ? If it doesn't, aquos sodiumhypochlorite could then be boiled to the salts formed. The right amount of water could then be added to the salts (NaClO3 & NaCl), NaCl would not solve and could easily be filtered out. Is any of this correct ?

Soulability :
NaClO3 -> 209g/100ml @ 20 C
NaCl -> 36g/100ml @ 20 C
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[*] posted on 20-5-2002 at 18:47


I really can't think of a simple solution to the inert-gas problem. Most of the time, the gas is going to get heated to autoignition temperature; however it will not combust if there is no oxygen present. Try boiling hexane and using the hexane vapors as an inert gas; higher autoignition temperature. I have produced CS2 which has an autoignition temperature of around 90C by heating sulfur and carbon in a pyrex flask at temperatures more like 500C; never have had any trouble. Mostly, just make sure you're using a flask, and do it outside (it case the gas being used does ignite). If it ignites while outside, it really doesn't matter.

I just looked up the solubility of sodium chlorate here: http://www.jtbaker.com/msds/S3314.htm according to them, 100g NaClO3 dissolves in 100g H2O at 20C.

If you placed 100g NaClO3 and 36g NaCl in 100mL of water, I believe about 73.5g NaClO3 and about 9.5g NaCl would be dissolved.

Therefore, the best method for preparing high-purity NaClO3 is the electrolysis method. However, if you just plan on using the NaClO3 for preparing ClO2, then high levels of contamination with NaCl is not to be worried about.




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[*] posted on 19-9-2002 at 01:21
A little accident


I tried making perchloric acid with my "professional" ;) equipment.
I used a three necked flask, a 70 degree adapter and a allin condenser. I measured out the right amount of oxalic acid and put it in the threee- necked flask. I heated the oxalic acid to it melted (90 - 80 degrees celsius). Then i added portions of Sodium chlorate (wich was made from NaClO decomp. and was very polluted). A yellowish-green gas developed at a great speed. I bubbled the gas trough cold water, and after five min. the water had turned yellow. Just as I leaved the lab to get some food, a explosion occured. I heard a farly high report, but no damage was done.

What could have been the reason for the explosion, ClO2 explosion or to high HClO4 conc. ?

Thanks
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[*] posted on 19-9-2002 at 04:33


Explosive decomposition of ClO2....



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[*] posted on 19-9-2002 at 09:53


What is the decomposition temp. of ClO2
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[*] posted on 19-9-2002 at 10:25


Chlorine oxides decompose violently in contact with organic matter. Since you used oxalic acid....



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[*] posted on 19-9-2002 at 10:26
Forgot something


To add, there is no temperature listed at which it explodes but it is very unpredictable. Treat like gaseous NI3.NH3



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[*] posted on 19-9-2002 at 10:58


I doubt it was the contact with oxalic acid that made the chlorine dioxide explode. This is where I got the facts

Maybe the collecting flask was a bit dirty ?




Respect Explosives
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[*] posted on 19-9-2002 at 16:57


Some Accidents Involving Perchloric Acid

1. Explosions may occur when 72% perchloric acid is used to determine chromium in steel, apparently due to the
formation of mixtures of perchloric acid vapor and hydrogen. These vapor mixtures can be exploded by the catalytic
action of steelparticles.2
2. Two workers are reported to have dried 11,000 samples of alkali-washed hydro-carbon gas with magnesium
Perchlorate over a period of 7 years without accident. However, one sample containing butyl fluoride caused a
purplediscoloration of the magnesium Perchlorate, with the subsequent explosion of the latter.2
3 . A worker using magnesium Perchlorate to dry argon reported an explosion andwarned that warming and
contact with oxidizable substances should be avoided.2
4. An explosion was reported when anhydrous magnesium Perchlorate used indrying unsaturated hydrocarbons was
heated to 220'C.2
5 . An explosive reaction takes place between perchloric acid and bismuth or certainof its alloys, especially during
electrolytic polishing.2,5
6. Several explosions reported as having occurred during the determination ofpotassium as the Perchlorate are
probably attributable to heating in the presenceof concentrated perchloric acid and traces of alcohol. An incident
in a French laboratory is typical: an experienced worker in the course of a separation ofsodium and potassium
removed a platinum crucible containing a few decigramsof material and continued the heating on a small gas flame.
An explosion pulverized the crucible, a piece of platinum entering the eye of the chemist.7
7. A violent explosion took place in an exhaust duct from a laboratory hood inwhich perchloric acid solution was being
fumed over a gas plate. It blew outwindows, bulged the exterior walls, lifted the roof, and extensively
damagedequipment and supplies. Some time prior to the explosion, the hood had beenused for the analysis of
miscellaneous materials. The explosion apparentlyoriginated in deposits of perchloric acid and organic material in the
hood andduct.8
8. A chemist was drying alcohol off a small anode over a Bunsen burner in a hoodreserved for tests involving
perchloric acid. An explosion tore the exhaust ductfrom the hood, bent a portion of the ductwork near the fan,
and blew out many panes of window glass.8
9. An employee dropped a 7-pound (3.2 kg) bottle of perchloric acid solution ona concrete floor. The liquid was
taken up with sawdust and placed in a covered, metal waste can. Four hours later, a light explosion blew open
the hinged cover of the can. A flash fire opened three sprinklers which promptly extinguished the fire.8
10. A 7-pound bottle of perchloric acid solution broke while an employee wasunpacking a case containing three bottles.
The spilled acid instantly set the wood floor on fire, but it was put out quickly with a soda-acid extinguisher.8
11. At a malleable iron foundry, perchloric acid had been used for about 4 years inthe laboratory for the determination
of the silicon contents of iron samples. Acast iron, wash-sink drain at the bench used for this purpose had
corroded and the leaking acid had soaked into the wood flooring, which was later ignited whilea lead joint was
being poured. This fire was extinguished and part of the woodflooring was removed. Later in the day, at a point
slightly removed from the location of the first fire, a similar fire occurred when hot lead was again spilled.This time
the fire flashed with explosive violence into the exhaust hood and stackabove the workbench. Laboratory
equipment and records were wetted downextensively and damaged.
12. A stone table of a fume hood was patched with a glycerin cement and severalyears later, when the hood was being
removed, the table exploded when a worker struck the stone with a chisel. The hood had been used for digestions
with perchloric acid and, presumably, acid spills had not been properly cleaned up.9
13. A conventional chemical hood normally used for other chemical reactions, including distillation and ashing of organic
materials, was also used during the same time for perchloric acid digestion. During a routine ashing procedure, the
hot gases went up the 12-inch tubular transit exhaust duct and one of a series of explosions occurred that tore the
duct apart at several angles and on the horizontal runs.9
14. During routine maintenance involving partial dismantling of the exhaust blower on a perchloric acid ventilating
system, a detonation followed a light blow with a hammer on a chisel held against the fan at or near the seal
between the rear cover plate and the fan casing. The intensity of the explosion was such that it was heard 4 miles
away. Of the three employees in the vicinity, one sustained face lacerations and slight eye injury; the second
suffered loss of four fingers on one hand and possible loss of sight in one eye; the third was fatally injured with the
6-inch chisel entering below his left nostril and embedded in the brain.9
15. A 6-pound (2.7 kilograms) bottle of perchloric acid broke and ran over a fairly large area of a wooden laboratory
floor. It was cleaned up, but some ran down over wooden joists. Several years later a bottle of sulfuric acid was
spilled in this same location and fire broke out immediately in the floor and the joists.9
16. A chemist reached for a body of perchloric acid stored on a window sill above a steam radiator. The bottle struck
the radiator, broke, and the acid flowed over the hot coils. Within a few minutes the wooden floor beneath the
radiator burst into flame.9
17. An explosion occurred when an attempt was made to destroy benzyl celluloses by boiling with perchloric acid.11
18. An explosion occurred as anhydrous perchloric acid was being prepared via sulfuric acid dehydration and extraction
with methylene chloride when a stopper was removed from the separatory flask.14
19. A rat carcass was dissolved in nitric acid, the fat skimmed off, and perchloric acid added. The mixture was
heated to dryness and touched, setting off an explosion that cracked the fume hood and nearly blew out the sash.16
20. A perchlorate-doped polyacetylene film was prepared and stored under argon in a seated vessel. Two weeks later,
the film detonated when the vessel top was being removed. Earlier safety testing failed to show any reaction to flame
or impact.17
21. Perchlorate-doped polyacetylene samples combusted violently in the oxygen atmosphere of a Schoniger flask.18
22. An explosion occurred in a fume hood upon ether drying of a second crop of crystals of hexaminechromium (111)
perchloratethatwere washed with absolute ethanol and anhydrous diethylether. Following aspiration of the ether
wash, the ether damp filter cake was agitated with a glass stirring rod and the mass detonated.19
23. Perchlorate-doped, highly conducting polythiophene Pt-CIO, exhibits excellent ambient stability, but the film should
not be heated above 1000C. Touching an extremely dry Pt-CIO, film (kept in a desiccator over P20,) with
tweezers might cause an explosion of the film.20
24. Some samples of rare earth organic fluoride were re-ashed with perchloric, sulfuric, and nitric acid in I -liter
beakers. One of the beakers started foaming, turned yellow, and then exploded. The surface of the hot plate
was bent downward, and the imprint of the beaker was left in the metal surface of the hot plate by the force of the
explosion.1
25. Drying an acetonitrile adduct of neodymium Perchlorate at SO'C in vacuumapparently produces a compound that
can detonate on mechanical contact

Any of those explain the explosion
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[*] posted on 19-9-2002 at 17:05


I hope this helps:

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
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[*] posted on 19-9-2002 at 22:05


still, ClO2 is the most widely used bleaching chemical in the pulp and paperindustry. In sweden alone several tens of thousands of tonnes of NaClO3 is manufacured everyyear for the sole purpose of making ClO2.

www.ekachemicals.com

so it can be handled safely in conctact with organic material, it is just that it is probably very difficult to do this in a lab.

/rickard
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[*] posted on 21-9-2002 at 14:30


I was recently researching perchloric acid, it appears to be a bastard of a chemical. Not only does it dissolve experimenters, it can spill onto wooden floorboards and either catch fire right now or wait for a few months/years and form a coating that is friction sensitive and burn/explode later. It also seems to create merry hell with fume cupboards.

I would like to hear from a person who regularly uses perchloric acid in their normal work.

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[*] posted on 1-10-2002 at 16:29


How about reacting a stoichemical amount of potassium perchlorate and conc. sulfuric acid, and distilling the resulting perchloric acid to tilt the equilibrium in the favorable direction? HClO4 boils at 39 degrees; concentrated H2SO4 boils at 290 degrees. Little bit of a difference there. :P

Although, I don't know if perchloric acid would enjoy being distilled... :o

David Hansen
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[*] posted on 1-10-2002 at 22:31


mmmmm,

ever heared somebody a big booom
by heating HClO4 on the open air or by
contact with draining chemicals?

Higher a concentration 50%, it`s a bad thing to cooking a soup with >75 C.

You can prepare >70% HClO4 by dropping up H2SO4 to KClO4 in a vacuum distillation-device and following all reakting, distil very careful with waterbad under vacuum !




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[*] posted on 2-10-2002 at 08:00


The boiling point of perchloric acid is 120,5C.



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[*] posted on 2-10-2002 at 08:01


HClO4 formes a aezotrope with water at 71 %, BP = 203 C.

Conentrated (> 90 %) can not be heated to its boiling point at atmospheric pressure, decompostion starts at 100 c or so.
decomposition starts with the acid changing colour to the redish , and very soon after that explodes.

If handling there must be a possibility to dump everything into water without a second of delay!!!!

Even at room temperature this can happen.

Less than 71 % it is generally considered safe, given standard precautions for a strong oxidizing acid forming explosive mixture with most organic materials..

It is a excellent reagence for wet-ashing filters , but needs much care in the process.

Industrially it is made by excess HCl and NaClO4 , NaCl preciptates and is filtered off, whereafter the HCl is removed by distillation. Left is NaClO4 dissolved in concentrated HClO4 wich is separated by vacuum distillation.

/rickard
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[*] posted on 3-10-2002 at 02:40


I`d read any time ago,
the bp of HClO4 is a this densitys:

1,53 g/cm3 =~ 160 C
1,68 g/cm3 => 198 C
?




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