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AndersHoveland
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Oxidation of Ammonium Perchlorate to Perchloric Acid
As ammonium perchlorate may be prepared from the fractional crystallization of sodium perchlorate and ammonium chloride, since ammonium perchlorate
has such a low solubility, the potential to obtain free perchloric acid from ammonium perchlorate could be useful. Even if this is not practical, the
oxidation of ammonium perchlorate is still an interesting and revealing subject.
It is not impossible for aqueous chlorine to oxidize ammonium perchlorate to free perchloric acid. However, the reaction exists in equilibrium, and
formation of perchloric acid is not very favorable. As perchloric acid begins to form, the equilibrium will become less and less favorable to the
generation of more acid. Essentially, only a small fraction of the beginning reactants will react. It is impossible to oxidize more than a small
fraction of ammonium ions using chlorine in a solution which is becoming acidified from the partial formation of perchloric acid. Small droplets of
oily nitrogen trichloride will appear, but it is not possible to obtain more than very dilute perchloric acid, which cannot be easily isolated from
the much larger quantity of ammonium perchlorate also dissolved. I had the idea of using chlorine to obtain perchloric acid before, but was told by
someone here that they had tried using ammonium sulfate and chlorine and it did not work. It has been observed that chlorine essentially does not
attack ammonium perchlorate, at least to any significant degree, but it should be noted that chlorine gas can react with a solution of ammonium
chloride, and especially ammonium sulfate, to form nitrogen trichloride, a dangerously sensitive explosive.
Interestingly, an alternate reaction is mentioned, one that utilizes aqua regia to oxidize the ammonia away from the ammonium salt. Apparently it is
intermediate nitrous acid that oxidizes the ammonium ions.
“reaction of ammonium perchlorate with nitric and hydrochloric acids, and then concentration at 198–200°C to eliminate the unreacted acids by
vacuum distillation:
34 NH4ClO4 +36 HNO3 + 8 HCl --> 34 HClO4 +4 Cl2 + 35 N2O + 73 H2O “
H. H. Willard,J. Am. Chem. Soc.34, 1480 (1912).
Chlorine gas may be bubbled into an aqueous solution of ammonium perchlorate for several hours with almost no observable reaction. (Any slight
oxidation may be due to dichlorine monoxide, Cl2O, which has a minute equilibrium in aqueous solutions of chlorine. Alternatively, the boiling may
have caused the traces of NCl3 that existed in equilibrium to silently decompose into nitrogen gas.)
(I also had the idea of "forcing" the reaction between ammonium perchlorate and chlorine, by subjecting the reaction to ultrasonic agitation (such as
from a common mystifier). This might cause decomposition of the small portion of NCl3, that exists in equilibrium, into N2 and Cl2, potentially
shifting the reaction forward.)
Neither does concentrated nitric acid oxidize ammonium perchlorate.
A mix of concentrated nitric (69% conc) and hydrochloric acids (35% conc) is capable of oxidizing ammonium perchlorate to perchloric acid. The
solution must be kept boiling or the reaction will be very slow. Less hydrochloric acid is consumed if it is gradually added over the course of the
reaction (20 minutes). The gases evolved from the reaction were passed through a solution of sodium hydroxide to remove the chlorine and nitrogen
dioxide gases which had formed. Surprisingly, the remaining gas contained 90% nitrous oxide (N2O), the rest apparently being nitrogen. Nitric oxide
was not observed, but may have been formed from the original reaction as it would have been oxidized and absorbed in the sodium hydroxide solution
because of the formation of hypochlorite from the chlorine. The gas above the boiling solution has a faint brownish color.
Procedure:
In a 2-L flask place 500g of ammonium perchlroate. Add 600 cm3 water, 410g of 68-70% nitric acid, heat to boiling. Place 105g hydrochloric acid of 37%
concentration in a dropping funnel that will gradually add its contents into the reaction flask so that the volume of the flask will remain fairly
constant despite some boiling out of the contents during the reaction. The hydrochloric acid is added more rapidly at first, then more slowly, over
the period of 25 minutes or longer. The boiling must be vigorous throughout this part of the procedure, which may last 45 minutes to an hour. After
the hydrochloric acid ceases to be added, water should be added to maintain the volume, as much water will boil out. After the reaction, the solution
is allowed to boil down, reducing the heat after the volume has decreased by half. Above 135°C, all the hydrochloric acid will have boiled out. The
heat is removed when fumes of perchloric acid appear, at which point the flask contains perchloric acid dihydrate, HClO4*(2)H2O. The acid should then
be free from ammonium salts, which can be tested by removing a small portion of the contents, and adding to an alkaline solution of potassium mercuric
iodide. If any ammonia is present a yellowish brown colored precipitate will form. The acid in the reaction flask will still contain some nitric
acid, and this can be avoided by using a somewhat larger quantity of hydrochloric acid in the procedure to react away all the nitric acid.
If formic acid is slowly added into a boiling solution of ammonium perchlorate and nitric acid, all of the ammonium ions in solution can be
completely oxidized. Both of these reactions are thought to be due to the intermediate formation of nitrous acid, HNO2, which is capable of oxidizing
ammonium ions. If, however, hydroiodic acid is slowly added to the boiling solution of ammonium perchlorate and nitric acid, the ammonium perchlorate
is not decomposed to any significant extent. It appears that although the hydroiodic acid initially reduces the nitric acid to form nitrous acid as an
intermediate, the nitrous acid is reduced by the hydroiodic acid at a much faster rate than it is formed. The oxidation of ammonium salts using nitric
acid proceeds much more rapidly, and gives higher yields, when hydrochloric acid is used, rather than formic acid, although more concentrated nitric
acid is required when hydrochloric acid is employed. A mixture of nitric oxide (NO) and nitrogen dioxide (NO2), obtained from the action of sulfuric
acid on sodium nitrite, was bubbled into a boiling solution of ammonium perchlorate. Although the reaction was very slow, some of the ammonium ions
were oxidized, leaving free perchloric acid in solution.
It is my opinion that the other oxidizing intermediates may possibly be of importance in the reactions described above, rather than, or in addition to
nitrous acid. In the case of aqua regia, nitrosyl chloride, ONCl, is likely responsible, which is known to form according to the equation,
(2)HNO3 + (6)HCl --> (4)H2O + (2)NOCl + (4)Cl2.
With the formic acid/nitric acid mixture, or with the NO2/NO gas, the reactive intermediate oxidizer is probably dinitrogen trioxide, N2O3, which
exists in equilibrium with both gaseous mixtures of NO2/NO and aqueous solutions of nitrous acid. Both NOCl and N2O3 would be expected to be capable
of oxidizing ammonium ions because both compounds can serve as oxidizing "bases" toward ammonium ions. Despite NOCl and N2O3 actually being acidic in
solution, they could potentially act as tempory bases because all that is needed is a small equilibrium. The free NH3 will be oxidized as it is
formed, shifting the equilibrium towards the right.
H3NH[+] Cl--N=O <==> H3N Cl--H NΞO[+]
N2O3 may react much more readily than HNO3 because the free hydrogen ion that would need to temporarily form as an intermediate is actually less
favorable than formation of a nitrosonium ion. Of course, nitrosonium ions hydrolyze in water to form hydronium ions, H3O[+], which are less acidic
(HNO2 is also formed from the hydrolysis of NO[+] )
It was observed that pure nitrogen dioxide oxidized ammonium perchlorate such that free perchloric acid could be obtained. The addition of nitric
oxide, or if oxygen, to the nitrogen dioxide did not observably affect the reaction. Indeed, no reaction was observed when pure nitric oxide was
bubbled into ammonium perchlorate. It was also observed that more than two molecules of NO2 formed for every molecule of perchloric acid. Despite
nitric oxide (NO) appearing to be irrelevent in the reaction, the consumption of excess NO2 in the reaction relative to the HClO4 that formed
suggested the following as a reaction:
(3)NO2 + H2O <==> NO + (2)HNO3
(*comment by me: If this is the case, then it may nevertheless suggest that N2O3 may be the actual oxidizing intermediate, and that addition of nitric
oxide to the reaction is irrelevent because nitric oxide will still exist in equilibrium even in an aqueous solution of "pure" nitrogen dioxide)
A.W. Knight. Undergraduate Thesis at California Institute of Technology (1992). "Perchloric Acid from Ammonium Perchlorate and Oxides of
Nitrogen
97.5% of the NH4ClO4 could be converted to HClO4 in this way.
Procedure for preparing Nitric Oxide
Bubble pure nitric oxide into an aqueous solution of ammonium perchlorate and nitric acid. The nitric oxide is produced by reaction of sodium nitrite
with dilute hydrochloric acid, with ferrous sulfate, FeSO4, also present to react with, and prevent the escape of, the nitrogen dioxide. The reactions
are:
(2)NaNO2 + (2)H2SO4 + (2)FeSO4 --> Fe2(SO4)3 + Na2SO4 + (2)H2O + NO
NO + HNO3 <==> HNO2 + NO2
For more information about NCl3 interactions and chemistry, see the thread in this forum, "Toying with NCl3 idea tidbit" -
http://www.sciencemadness.org/talk/viewthread.php?tid=17235
[Edited on 22-12-2011 by AndersHoveland]
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woelen
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This procedure is much like the experiment I did with NH4ClO4, HNO3 and HCl. See the other thread on perchloric acid, to which I added my experimental
results. The method looks promising on paper, but in practice I was disappointed by the results. The acid simply is boiled off and NH4ClO4 remains
behind in solution and crystallizes when the total volume drops below a certain value.
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AJKOER
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Here is an old Sciencemadness thread on shortcuts to perchloric acid.
http://www.sciencemadness.org/talk/viewthread.php?action=pri...
A must read on what not to do.
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Pulverulescent
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| Quote: | hissingnoise - 26-12-2002 at 15:48
Does anyone know if hcl can be electrooxidised to hclo3 and hclo4 without using alkali metal salts.
I know from ex. that nh4cl cannot be oxidised electrolytically; the positive ammonium ion isn't a metal.
It shouldn't be tried because poisonous cloramines(vapour) are formed.
Thanks |
That, BTW, was my first post . . .
P
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vulture
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I fail to see how ammoniumperchlorate can be "oxidized" to perchloric acid. There is no oxidation taking place.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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weiming1998
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Instead of overcomplicating the production of perchloric acid from a perchlorate salt, how about : 2NH4ClO4+H2SO4====>(NH4)2SO4+2HClO4. There's your
perchloric acid. If you are scared of anhydrous perchloric acid exploding, you can always use <60% sulfuric acid and a perchlorate salt.
[Edited on 7-2-2012 by weiming1998]
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AndersHoveland
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There are, of course, several other ways to prepare perchloric acid, but this thread was meant to specifically discuss the feasibility of oxidizing
the ammonia away from NH4ClO4 to leave perchloric acid.
Quote: Originally posted by vulture  | | I fail to see how ammoniumperchlorate can be "oxidized" to perchloric acid. There is no oxidation taking place. |
Sorry if my post was unnecessarily confusing. I wanted to provide all the reaction details and convey all my relevant thoughts. To summarise, NH4ClO4
can be oxidized to perchloric acid by either distilling with aqua regia, in the presence of the oxidation of formic acid by nitric acid, or by nitrous
acid or nitrogen dioxide . But NH4ClO4 is not oxidized by concentrated nitric acid alone, and is essentially unaffected by chlorine.
| Quote: Originally posted by weiming1998 | | Instead of overcomplicating the production of perchloric acid from a perchlorate salt, how about : 2NH4ClO4+H2SO4====>(NH4)2SO4+2HClO4. There's your
perchloric acid. |
Unfortunately, ammonium perchlorate is much less soluble than ammonium sulfate. So it would not be possible to separate out the ammonium sulfate by
fractional crystallisation. Perhaps you mean distillation at reduced pressure? It would need reduced pressure, because hot acidified perchlorate would
just oxidize (and be decomposed by) the ammonium ions.
This leads to an interesting thought. Could careful decomposition and distillation of NH4ClO4 lead to perchloric acid?
6 NH4ClO4 --> 8 H2O + Cl2 + 3 N2 + 4 HClO4 ?
This is probably unlikely, however. Ammonium perchlorate is apparently decomposed by heat into ammonium chloride, oxygen and chlorine (P.
Groth), or into water, oxygen, nitrogen, and chlorine (M. Bertnelot).
[Edited on 7-2-2012 by AndersHoveland]
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Pulverulescent
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KClO<sub>4</sub> is the least soluble of the perchlorates!
Metathesis to KClO<sub>4</sub> of the ammonium salt is straightforward and although KCl is fairly soluble @ O°C, chilling to -20°C or
below might precipitate most, if not all of the KCl!
P
"I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones"
A Einstein
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AndersHoveland
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I did find one interesting piece of information:
| Quote: |
"During the the concentration of an aqueous solution of ammonium perchlorate some ammonia is lost, and the solution becomes acid."
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A comprehensive treatise on inorganic and theoretical chemistry, Volume 2, p397, Joseph William Mellor
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weiming1998
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| Quote: Originally posted by AndersHoveland | There are, of course, several other ways to prepare perchloric acid, but this thread was meant to specifically discuss the feasibility of oxidizing
the ammonia away from NH4ClO4 to leave perchloric acid.
| Quote: Originally posted by vulture | | I fail to see how ammoniumperchlorate can be "oxidized" to perchloric acid. There is no oxidation taking place. |
Sorry if my post was unnecessarily confusing. I wanted to provide all the reaction details and convey all my relevant thoughts. To summarise, NH4ClO4
can be oxidized to perchloric acid by either distilling with aqua regia, in the presence of the oxidation of formic acid by nitric acid, or by nitrous
acid or nitrogen dioxide . But NH4ClO4 is not oxidized by concentrated nitric acid alone, and is essentially unaffected by chlorine.
| Quote: Originally posted by weiming1998 | | Instead of overcomplicating the production of perchloric acid from a perchlorate salt, how about : 2NH4ClO4+H2SO4====>(NH4)2SO4+2HClO4. There's your
perchloric acid. |
Unfortunately, ammonium perchlorate is much less soluble than ammonium sulfate. So it would not be possible to separate out the ammonium sulfate by
fractional crystallisation. Perhaps you mean distillation at reduced pressure? It would need reduced pressure, because hot acidified perchlorate would
just oxidize (and be decomposed by) the ammonium ions.
This leads to an interesting thought. Could careful decomposition and distillation of NH4ClO4 lead to perchloric acid?
6 NH4ClO4 --> 8 H2O + Cl2 + 3 N2 + 4 HClO4 ?
[Edited on 7-2-2012 by AndersHoveland] |
This? 2NH4ClO4+Na2CO3==heat===>2NH3+CO2+H2O+NaClO4
2NaClO4+H2SO4=====> 2HClO4+Na2SO4. Na2SO4 is relatively insoluble even in cold, pure water(4g/100ml water at 0 degrees celsius), let alone
perchloric acid/water solution. Should be pretty easy to separate. No need for those (unverified) NOCl oxidations of the NH4 ion and the like.
34 NH4ClO4 +36 HNO3 + 8 HCl --> 34 HClO4 +4 Cl2 + 35 N2O + 73 H2O
Your molecules don't match up. Taking away the H+ from the NH4 for perchloric acid and the N2O, you actually have 138 hydrogens and 72 oxygens left.
Add on the hydrogen from 8HCl and you have 146 hydrogens and 72 oxygens. Now, double 72 is 144, so there are still two hydrogens left in your
equation.
[Edited on 7-2-2012 by weiming1998]
Sorry, my mistake. Too tired today. The NH4 is oxidized to N2O, not reduced. But still, the N in NH4 is oxidized from -3 to +1, one oxidation state
compensating for HClO4, so 3 oxidation states oxidized by nitric acid. But the N in nitric acid is reduced from +5 to +1, and even if the nitric acid
is also reduced by the Cl-, there are still some nitric acid reduced by nothing. So your equation is incorrect
[Edited on 7-2-2012 by weiming1998]
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AndersHoveland
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"THE PREPARATION OF PERCHLORIC ACID", H. H. Willard,
J. Am. Chem. Soc., 1912, 34 (11), pp 1480–1485
http://pubs.acs.org/doi/abs/10.1021/ja02212a006
Willard decomposed ammonium perchlorate by boiling a solution of it with aqua regia, evaporating off the excess of the latter, to obtain perchloric
acid. The perchloric acid takes no part in the destruction of the ammonia. Distillation at a pressure of about 100 mmHg is recommended. The acid
obtained either by evaporation, or subsequent distillation, corresponded to the formula HClO4·2H2O. He found that chlorine gas alone passed into the
boiling solution of NH4ClO4 had little effect.
Can one of the moderators save this to the library?
http://thesis.library.caltech.edu/4743/1/Adams_hc_1925.pdf
| Quote: |
A mix of concentrated nitric (69% conc) and hydrochloric acids (35% conc) oxidized ammonium perchlorate to perchloric acid. The solution was kept
continuously boiling. Less hydrochloric acid is consumed if it is gradually added over the course of the reaction (20 minutes). The gases evolved from
the reaction were passed through a solution of sodium hydroxide to remove the chlorine and nitrogen dioxide gases which had formed. The remaining gas
contained 90% nitrous oxide (N2O), the rest apparently being nitrogen. The gas above the boiling solution had a faint brownish color.
Procedure:
In a 2-L flask place 500g of ammonium perchlroate. Add 600 cm3 water, 410g of 68-70% nitric acid, heat to boiling. Place 105g hydrochloric acid of 37%
concentration in a dropping funnel that will gradually add its contents into the reaction flask so that the volume of the flask will remain fairly
constant despite some boiling out of the contents during the reaction. The hydrochloric acid is added more rapidly at first, then more slowly, over
the period of 25 minutes or longer. The boiling must be vigorous throughout this part of the procedure, which may last 45 minutes to an hour. After
the hydrochloric acid ceases to be added, water should be added to maintain the volume, as much water will boil out. After the reaction, the solution
is allowed to boil down, reducing the heat after the volume has decreased by half. Above 135°C, all the hydrochloric acid will have boiled out. The
heat is removed when fumes of perchloric acid appear, at which point the flask contains perchloric acid dihydrate, HClO4*(2)H2O. The acid should then
be free from ammonium salts, which can be tested by removing a small portion of the contents, and adding to an alkaline solution of potassium mercuric
iodide. If any ammonia is present a yellowish brown colored precipitate will form. The acid in the reaction flask will still contain some nitric acid,
and this can be avoided by using a somewhat larger quantity of hydrochloric acid in the procedure to react away all the nitric acid.
If formic acid is slowly added into a boiling solution of ammonium perchlorate and nitric acid, all of the ammonium ions in solution can be completely
oxidized. Both of these reactions are thought to be due to the intermediate formation of nitrous acid, HNO2, which is capable of oxidizing ammonium
ions. If, however, hydroiodic acid is slowly added to the boiling solution of ammonium perchlorate and nitric acid, the ammonium perchlorate is not
decomposed to any significant extent. It appears that although the hydroiodic acid initially reduces the nitric acid to form nitrous acid as an
intermediate, the nitrous acid is reduced by the hydroiodic acid at a much faster rate than it is formed. The oxidation of ammonium salts using nitric
acid proceeds much more rapidly, and gives higher yields, when hydrochloric acid is used, rather than formic acid, although more concentrated nitric
acid is required when hydrochloric acid is employed. A mixture of nitric oxide (NO) and nitrogen dioxide (NO2), was bubbled into a boiling solution of
ammonium perchlorate, leaving free perchloric acid |
[Edited on 7-2-2012 by AndersHoveland]
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vulture
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I don't want to rain on your parade, but don't you think using aqua regia to produce perchloric acid from ammonium perchlorate is both a waste of aqua
regia (and thus nitric acid) and ammonium perchlorate? It's not like ammonium perchlorate is OTC and anybody here producing it is likely making it
from sodium or potassium perchlorate, which would provide more convenient avenues for producing perchloric acid.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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dann2
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Believe it or not Ammonium Perchlorate seem to be more easy to come by than Sodium Perchlorate in Europe.
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AndersHoveland
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Reacting nitrogen dioxide with a boiling solution of NH4ClO4 is a potential route to obtain perchloric acid.
Nitrogen dioxide can easily be prepared by acidifying a mix of NaNO3 and NaNO3 with bisulfate or dilute sulfuric acid.
Yes, the fractional crystallization of NH4ClO4 from NaClO4 is extra trouble, but the advantage of this route would be that the resulting perchloric
acid will be of higher purity, free from traces of NaCl that result from the NaClO4 + HCl route. The oxidation of NH4ClO4 route may also be less
demanding and somewhat safer than the distillation of KClO4 with sulfuric acid. The distillation for the NH4ClO4 route operates at a lower
temperature, and has the advantage that the final perchloric acid product remains in the original flask rather than being collected in the distillate.
So the NH4ClO4+NO2 route could potentially be more practical depending on personal preference, the regents and equipment available, and the required
purity of the end product.
But even if it was less practical, it is still an interesting reaction that some members might want to try.
NH4ClO4 can sometimes be purchased as hobby rocket fuel oxidizer.
http://www.highqualitychems.com/servlet/StoreFront
[Edited on 7-2-2012 by AndersHoveland]
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weiming1998
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| Quote: Originally posted by AndersHoveland | Reacting nitrogen dioxide with a boiling solution of NH4ClO4 is a potential route to obtain perchloric acid.
Nitrogen dioxide can easily be prepared by acidifying a mix of NaNO3 and NaNO3 with bisulfate or dilute sulfuric acid.
Yes, the fractional crystallization of NH4ClO4 from NaClO4 is extra trouble, but the advantage of this route would be that the resulting perchloric
acid will be of higher purity, free from traces of NaCl that result from the NaClO4 + HCl route. The oxidation of NH4ClO4 route may also be less
demanding and somewhat safer than the distillation of KClO4 with sulfuric acid. The distillation for the NH4ClO4 route operates at a lower
temperature, and has the advantage that the final perchloric acid product remains in the original flask rather than being collected in the distillate.
So the NH4ClO4+NO2 route could potentially be more practical depending on personal preference, the regents and equipment available, and the required
purity of the end product.
But even if it was less practical, it is still an interesting reaction that some members might want to try.
NH4ClO4 can sometimes be purchased as hobby rocket fuel oxidizer.
http://www.highqualitychems.com/servlet/StoreFront
[Edited on 7-2-2012 by AndersHoveland] |
No.
1, NO2 is almost impossible to dissolve in boiling water
2, The reaction still doesn't make sense, http://en.wikipedia.org/wiki/Ammonium_perchlorate
You see the solubility? 57grams per 100ml of water. Ammonium nitrate has a solubility of something like 1000 grams/100ml. Nitric acid is a borderline
strong acid, while perchloric acid is a strong acid that is as strong/stronger than sulfuric acid. Nothing should form. Plus, even the equilibrium of
ions doesn't favour the reaction. You could think of it as NH4ClO4+HNO3<===>NH4NO3+HClO4. Both the differing strengths of the acid, plus
precipation (NH4ClO4 is about 20 times less soluble than NH4NO3 in the conditions you described), will drive the reaction strongly to the left. Even
if you have traces of HClO4 when you first started, it will change into HNO3 when you try to heat up the solution.
[Edited on 8-2-2012 by weiming1998]
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AndersHoveland
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| Quote: Originally posted by weiming1998 |
1, NO2 is almost impossible to dissolve in boiling water
2, The reaction still doesn't make sense, http://en.wikipedia.org/wiki/Ammonium_perchlorate
You see the solubility? 57grams per 100ml of water. Ammonium nitrate has a solubility of something like 1000 grams/100ml. Nitric acid is a borderline
strong acid, while perchloric acid is a strong acid that is as strong/stronger than sulfuric acid. Nothing should form. Plus, even the equilibrium of
ions doesn't favour the reaction. You could think of it as NH4ClO4+HNO3<===>NH4NO3+HClO4. Both the differing strengths of the acid, plus
precipation (NH4ClO4 is about 20 times less soluble than NH4NO3 in the conditions you described), will drive the reaction strongly to the left. Even
if you have traces of HClO4 when you first started, it will change into HNO3 when you try to heat up the solution.
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I do not understand what you are trying to say.
The NO2 needs to be continuously passed into the boiling solution. Which reaction are you referring to?
| Quote: |
It was observed that pure nitrogen dioxide oxidized ammonium perchlorate such that free perchloric acid could be obtained. The addition of nitric
oxide, or if oxygen, to the nitrogen dioxide did not observably affect the reaction.
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I specifically stated that nitric acid alone has no effect on NH4NO3. Read the paper in that link, there was only a reaction when nitric oxide was
passed into the NH4ClO4 and HNO3. The nitric oxide reduces the dilute nitric acid to nitrogen dioxide (actually there is an equilibrium), or further
to nitrous acid. It is the nitrous acid that presumably oxidizes the ammonium cations.
[Edited on 8-2-2012 by AndersHoveland]
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weiming1998
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| Quote: Originally posted by AndersHoveland | | Quote: Originally posted by weiming1998 |
1, NO2 is almost impossible to dissolve in boiling water
2, The reaction still doesn't make sense, http://en.wikipedia.org/wiki/Ammonium_perchlorate
You see the solubility? 57grams per 100ml of water. Ammonium nitrate has a solubility of something like 1000 grams/100ml. Nitric acid is a borderline
strong acid, while perchloric acid is a strong acid that is as strong/stronger than sulfuric acid. Nothing should form. Plus, even the equilibrium of
ions doesn't favour the reaction. You could think of it as NH4ClO4+HNO3<===>NH4NO3+HClO4. Both the differing strengths of the acid, plus
precipation (NH4ClO4 is about 20 times less soluble than NH4NO3 in the conditions you described), will drive the reaction strongly to the left. Even
if you have traces of HClO4 when you first started, it will change into HNO3 when you try to heat up the solution.
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I do not understand what you are trying to say.
The NO2 needs to be continuously passed into the boiling solution. Which reaction are you referring to?
I specifically stated that nitric acid alone has no effect on NH4NO3. Read the paper in that link, there was only a reaction when nitric oxide was
passed into the NH4ClO4 and HNO3. The nitric oxide reduces the dilute nitric acid to nitrogen dioxide (actually there is an equilibrium), or further
to nitrous acid. It is the nitrous acid that presumably oxidizes the ammonium cations.
[Edited on 8-2-2012 by AndersHoveland] |
So nitrous acid. http://en.wikipedia.org/wiki/Nitrous_acid
it decomposes extremely quickly, even when the water is warm or when it is even slightly concentrated, and you are talking about it in boiling water?
Sorry, it wouldn't work.
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AndersHoveland
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Perhaps you did not read the links in the previous post.
http://pubs.acs.org/doi/abs/10.1021/ja02212a006
http://thesis.library.caltech.edu/4743/1/Adams_hc_1925.pdf
I have summarised the information found in both these links.
| Quote: |
Willard decomposed ammonium perchlorate by boiling a solution of it with aqua regia, evaporating off the excess of the latter, to obtain perchloric
acid. The perchloric acid takes no part in the destruction of the ammonia. Distillation at a pressure of about 100 mmHg is recommended. The acid
obtained either by evaporation, or subsequent distillation, corresponded to the formula HClO4·2H2O. He found that chlorine gas alone passed into the
boiling solution of NH4ClO4 had little effect.
reaction of ammonium perchlorate with nitric and hydrochloric acids, and then concentration at 198–200°C to eliminate the unreacted acids by vacuum
distillation.
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| Quote: Originally posted by weiming1998 | 34 NH4ClO4 +36 HNO3 + 8 HCl --> 34 HClO4 +4 Cl2 + 35 N2O + 73 H2O
Your molecules don't match up. Taking away the H+ from the NH4 for perchloric acid and the N2O, you actually have 138 hydrogens and 72 oxygens left.
Add on the hydrogen from 8HCl and you have 146 hydrogens and 72 oxygens. Now, double 72 is 144, so there are still two hydrogens left in your
equation.
Edit:
Sorry, my mistake. Too tired today. The NH4 is oxidized to N2O, not reduced. But still, the N in NH4 is oxidized from -3 to +1, one oxidation state
compensating for HClO4, so 3 oxidation states oxidized by nitric acid. But the N in nitric acid is reduced from +5 to +1, and even if the nitric acid
is also reduced by the Cl-, there are still some nitric acid reduced by nothing. So your equation is incorrect
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34 NH4ClO4 +36 HNO3 + 8 HCl --> 34 HClO4 +4 Cl2 + 35 N2O + 73 H2O
The equation balances. An unbalanced form of this equation is found in the original source. The formation of the indicated products were supported by
experimental evidence. I just later did the math to make it a balanced equation.
As the equation does balance, I do not know what you mean by "there are still some nitric acid reduced by nothing". If it was reduced by "nothing",
there would have to also be some reducing atoms appearing out of nothing, which there is not. In other words, try to write any type of false equation
reaction where something is reduced from nothing where the equation still balances. I do not think this is even possible.
I do not know what you mean when you say it would not work. I have presented the experimental results from the literature, and added my own
commentary.
Aqua regia was shown to oxidize ammonium perchlorate, yet neither concentrated nitric acid alone, nor chlorine showed any significant reaction. The
literature sites nitrous acid as the most likely intermediate mechanism of oxidation, but you can speculate about other potential mechanisms if you
are not satisfied with that explanation.
[Edited on 8-2-2012 by AndersHoveland]
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woelen
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I also think that aqua regia may be capable of oxidizing some of the ammonium ions of ammonium perchlorate, but as I stated before in a few posts, in
practice this reaction does not work as nice as the paper suggests. At best a small part of the ammonium ions are oxidized to N2 or N2O. I found this
method of preparing HClO4 from NH4ClO4 rather disappointing. When the aqua regia is boiled, then a lot of gas is driven off (ONCl and Cl2) and even
with a long reflux condenser this simply escapes from the liquid (because ONCl and Cl2 are gases).
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weiming1998
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| Quote: Originally posted by AndersHoveland | Perhaps you did not read the links in the previous post.
http://pubs.acs.org/doi/abs/10.1021/ja02212a006
http://thesis.library.caltech.edu/4743/1/Adams_hc_1925.pdf
I have summarised the information found in both these links.
| Quote: |
Willard decomposed ammonium perchlorate by boiling a solution of it with aqua regia, evaporating off the excess of the latter, to obtain perchloric
acid. The perchloric acid takes no part in the destruction of the ammonia. Distillation at a pressure of about 100 mmHg is recommended. The acid
obtained either by evaporation, or subsequent distillation, corresponded to the formula HClO4·2H2O. He found that chlorine gas alone passed into the
boiling solution of NH4ClO4 had little effect.
reaction of ammonium perchlorate with nitric and hydrochloric acids, and then concentration at 198–200°C to eliminate the unreacted acids by vacuum
distillation.
|
| Quote: Originally posted by weiming1998 | 34 NH4ClO4 +36 HNO3 + 8 HCl --> 34 HClO4 +4 Cl2 + 35 N2O + 73 H2O
Your molecules don't match up. Taking away the H+ from the NH4 for perchloric acid and the N2O, you actually have 138 hydrogens and 72 oxygens left.
Add on the hydrogen from 8HCl and you have 146 hydrogens and 72 oxygens. Now, double 72 is 144, so there are still two hydrogens left in your
equation.
Edit:
Sorry, my mistake. Too tired today. The NH4 is oxidized to N2O, not reduced. But still, the N in NH4 is oxidized from -3 to +1, one oxidation state
compensating for HClO4, so 3 oxidation states oxidized by nitric acid. But the N in nitric acid is reduced from +5 to +1, and even if the nitric acid
is also reduced by the Cl-, there are still some nitric acid reduced by nothing. So your equation is incorrect
|
34 NH4ClO4 +36 HNO3 + 8 HCl --> 34 HClO4 +4 Cl2 + 35 N2O + 73 H2O
The equation balances. An unbalanced form of this equation is found in the original source. The formation of the indicated products were supported by
experimental evidence. I just later did the math to make it a balanced equation.
As the equation does balance, I do not know what you mean by "there are still some nitric acid reduced by nothing". If it was reduced by "nothing",
there would have to also be some reducing atoms appearing out of nothing, which there is not. In other words, try to write any type of false equation
reaction where something is reduced from nothing where the equation still balances. I do not think this is even possible.
I do not know what you mean when you say it would not work. I have presented the experimental results from the literature, and added my own
commentary.
Aqua regia was shown to oxidize ammonium perchlorate, yet neither concentrated nitric acid alone, nor chlorine showed any significant reaction. The
literature sites nitrous acid as the most likely intermediate mechanism of oxidation, but you can speculate about other potential mechanisms if you
are not satisfied with that explanation.
[Edited on 8-2-2012 by AndersHoveland] |
Ok, that works now. Another mistake by me. I would think that the reaction mechanism is oxidation of the NH4+ ion by NOCl instead of HNO2. Something
like this: 2NH4ClO4+ HNO3+2NOCl===>2N2O+Cl2+2H2O+NO. Would this equation work?
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Rosco Bodine
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| Quote: Originally posted by woelen | | I also think that aqua regia may be capable of oxidizing some of the ammonium ions of ammonium perchlorate, but as I stated before in a few posts, in
practice this reaction does not work as nice as the paper suggests. At best a small part of the ammonium ions are oxidized to N2 or N2O. I found this
method of preparing HClO4 from NH4ClO4 rather disappointing. When the aqua regia is boiled, then a lot of gas is driven off (ONCl and Cl2) and even
with a long reflux condenser this simply escapes from the liquid (because ONCl and Cl2 are gases). |
It could very likely be that when you scaled down the experiment which was reported by Willard it was not convenient at the smaller scale to reproduce
the dropwise addition rate of HCl at 2% unless you were using a metering pump injection like a stepper driven hypodermic syringe and capillary tubing.
Of course this could have been managed under the contingency of using more acids for adjustment to the condition where everything is added in a lump
at the beginnning, as reported by Willard. I am thinking the Willard synthesis is probably scale sensitive, since scale would have definite bearing
on this type of reaction where a boiling liquid is contacting a gaseous reactant and the reaction may be occurring in the film of sheeting return
liquid phase flowing across the glass as well as the bubble film interface of the bubbling liquid. Indeed such a scheme could have a physical
dimension criticality which makes the experiment highly scale sensitive. If this is true, then what Willard reported could be absolutely true for the
precise scale reaction as Willard reported, while changing that scale could monkey wrench the entire reaction which may have to be reoptimized
considerably for a differing scale.
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mr.crow
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I don't want to sidetrack the thread, but does anyone have a procedure for perchloric acid from barium perchlorate and H2SO4?
Double, double toil and trouble; Fire burn, and caldron bubble
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Pulverulescent
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Adding sulphuric acid slowly and with stirring to a cold, saturated soln of the perchlorate should work quite well . . .
How concentrated the HClO<sub>4</sub> would be is not something I know, but at least, if the stoichiometry is good, the acid should be of
reasonable purity!
Chilling the soln before filtering is always a good idea, BTW!
P
"I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones"
A Einstein
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mr.crow
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Thanks. Also, what is the best way to distill it? Just a small amount. Or maybe the trace amounts of excess barium or H2SO4 won't be a problem
Double, double toil and trouble; Fire burn, and caldron bubble
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dann2
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Hope this was not posted before:
Also some reading on Perk. acid:
http://yarchive.net/chem/perchloric_acid.html
Attachment: Stenzel_rw_1921[1].pdf (441kB)
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