Sciencemadness Discussion Board

KClO3 and H2SO4 reaction

condennnsa - 22-8-2010 at 08:52



Hello, i'm a little puzzled about this reaction.

I added 4 ml 95% sulfuric acid to a small beaker, and 1 gram of KClO3.


It reacted coloring the liquid to a red/brown color (just like NO2 color), which i suppose is chloric acid.
But to my surprise there was also a gas being produced. It smelled strongly of chlorine, but was more yellow in color. I would guess it's either Cl2 , or ClO2.

I found different references saying that this reaction makes chloric acid, and others saying it makes perchloric acid. Which one is true?

Or is it possible that the red/brown liquid i saw was Cl2O7, considering there was excess sulfuric acid?

What does this reaction look like?

The resulting solution was phenomenally reactive, on contact with any piece of paper or sugar granules, it popped violently, more like the sound of a detonation rather than simply burning.

thanks

DJF90 - 22-8-2010 at 09:56

The yellow gas is indeed chlorine dioxide. I did this as a kid and ended up with a purple gushing flame about a foot and half long! Quite spectacular...

woelen - 22-8-2010 at 11:48

First a word of warning! Please don't use such large quantities for this experiment. You were lucky that the whole mess did not explode. An explosion of 4 ml of concentrated sulphuric acid with 1 gram of potassium chlorate can give NASTY burns, sprayed all over your body, not to speak of the glass shrapnel that will penetrate your body!

The reaction which occurs first is formation of HClO3, which immediately disproportionates into HClO4 and ClO2 (and also some Cl2, O2 and H2O). The ClO2 gives the red/brown color in the liquid and also is the intense yellow gas above the liquid. It is extremely unstable and easily explodes. The HClO4 also is very dangerous, because here, it is more or less anhydrous and this is a very reactive and dangerous compound, which ignites and frequently explodes in contact with organics like paper, sugar, cotton, human skin and human hair.

Please don't do this again with these quantities. If you really want to try again, then take a small spatula of KClO3 and add 2 or 3 drops of concentrated sulphuric acid to this. With that small quantity you also can study the properties of this mix. An do not forget to have goggles in front of your eyes!

[Edited on 22-8-10 by woelen]

Formatik - 22-8-2010 at 16:53

The interaction of sulfuric acid and potassium chlorate was described here and in the hypergolics thread a bit. Explosions occurring from mixing these two is not untypical, being due to the highly explosive nature of ClO2. The perchlorate you can not obtain readily, other than as the perchlorate salt (KClO4) which is what results. Though this acid is too hazardous to use for that purpose.

The WiZard is In - 24-8-2010 at 08:08

Quote: Originally posted by Formatik  
The interaction of sulfuric acid and potassium chlorate was described here and in the hypergolics thread a bit. Explosions occurring from mixing these two is not untypical, being due to the highly explosive nature of ClO2. The perchlorate you can not obtain readily, other than as the perchlorate salt (KClO4) which is what results. Though this acid is too hazardous to use for that purpose.


Noted in passing :—

Gilbert Gordon & et al
The Chemistry of Chlorine Dioxide
Edgewood Arsenal Special Publication
EASP 1200-7
AD 743384
June 1972
286 pages


I do not find this available for download at the usual place,
however, you could get a copy from the NTIS, or if you are
truly driven (assuming I can find it) you can have my
micro fiche copy.

I would not spend a lot of money for a copy.

Chlorine dioxide

The WiZard is In - 25-8-2010 at 07:37

On Effn' Science [G4tv] last night they demonstrated the
energetic reaction between sodium chlorite and formaldehyde.
A reaction used to produce chlorine dioxide for industrial bleaching.

Their science needs a little work. I doubt the attraction
between atoms in a molecule is magnetic, and magnets are
not positive and negative.

A few years ago I made magnets with only north or south
poles, however, there was no market for them so I stopped.

watson.fawkes - 25-8-2010 at 15:55

Quote: Originally posted by The WiZard is In  
A few years ago I made magnets with only north or south poles, however, there was no market for them so I stopped.
You should have offered a monopoly on these to some theoretical physicist.

Formatik - 29-8-2010 at 10:41

Quote: Originally posted by The WiZard is In  

Noted in passing :—

Gilbert Gordon & et al
The Chemistry of Chlorine Dioxide
Edgewood Arsenal Special Publication
EASP 1200-7
AD 743384
June 1972
286 pages


I do not find this available for download at the usual place,
however, you could get a copy from the NTIS, or if you are
truly driven (assuming I can find it) you can have my
micro fiche copy.

I would not spend a lot of money for a copy.


There is quite a bit of info on ClO2 in Gmelin's Handbuch. This is the most convenient resource for me. It's very condensed and gives me usually what I'm are looking for. In concentrated form, ClO2 is extremely dangerous to handle. In dilute form (like around 10%), it is fairly harmless. ClO2 has triggers, especially relevant to concentrated forms. Triggers like heat, light (diffused daylight or sunlight), shock, and oxidizables (organics, cork, rubber, etc). Also been mentioned a bit on this forum before.

blogfast25 - 29-8-2010 at 12:14

Quote: Originally posted by watson.fawkes  
Quote: Originally posted by The WiZard is In  
A few years ago I made magnets with only north or south poles, however, there was no market for them so I stopped.
You should have offered a monopoly on these to some theoretical physicist.


What do you mean? So he discovered magnetic monopoles, that's nothing to the Wizard, you should see his collection of G-d particles! :D

condennnsa - 2-9-2010 at 02:54

Quote: Originally posted by woelen  
The reaction which occurs first is formation of HClO3, which immediately disproportionates into HClO4 and ClO2 (and also some Cl2, O2 and H2O).


Would this reaction be a viable route to perchloric acid, provided that I don't have a perchlorate salt?

For example, would it be safe to mix stoichiometric H2SO4 and KClO3 in a remote place, then leave it a couple of days to allow the ClO2 gas to escape, then distill the perchloric acid, like in the nitric acid synthesis from nitrate + H2SO4?

Quieraña - 25-6-2020 at 20:51

There's this Channel on YouTube called 'be rainbowed' and The person talks about using beta lasers on a very long magnet that gets cut you got to watch the video it's it's very it's not I'm not opposed as how it how to strengthen American something about Aurora blades using the name from Ready Player one and a couple other things for movies but referencing science is all there please check it out lasers are all about that to Jama lasers for me on memes. Powered ridiculous quantum what is stuff

Tsjerk - 26-6-2020 at 00:45

Quote: Originally posted by condennnsa  
Quote: Originally posted by woelen  
The reaction which occurs first is formation of HClO3, which immediately disproportionates into HClO4 and ClO2 (and also some Cl2, O2 and H2O).


Would this reaction be a viable route to perchloric acid, provided that I don't have a perchlorate salt?

For example, would it be safe to mix stoichiometric H2SO4 and KClO3 in a remote place, then leave it a couple of days to allow the ClO2 gas to escape, then distill the perchloric acid, like in the nitric acid synthesis from nitrate + H2SO4?



If you're skilled in micro distillations and are happy with 100 mg, of course. If you want to make more... you will really want to do this remotely. Don't spend too much on the remote control though as you will blow it up.

woelen - 28-6-2020 at 11:34

The reaction, I described 10 years ago is NOT a viable route to perchlorates!

What can be done is very carefully heating KClO3 to just over its melding point in an absolutely clean glass test tube.Keep heating gently and keep the mix just molten. There will be slow production of oxygen and after a while, the mix solidifies. You should NOT make the heating stronger, just let it solidify while heating gently in the same way. When the mix is completely solid, then stop heating.

Your solid is a mix of KClO4 and KCl and a little remaining KClO3. Dissolve this mix in as little as possible of 10% HCl and boil for a while. The liquid will turn yellow (Cl2 and dilute ClO2, no need to worry about explosions here). On cooling down you will get crystals of KClO4. KClO4 can be purified very easily, because it dissolves only very sparingly in cold water, while it dissolves quite well in hot water.

The most dangerous part of this synthesis is the heating of the KClO3 and keeping it just molten. It is easy to overheat the mix. That may lead to violent decomposition, with production of a lot of oxygen and possible eruption of the molten mass from the test tube! Also, when you do this reaction, use absolutely clean glass and use KClO3 which is known to be totally free of organic impurities, such as dust, paper fibers and that kind of things. A good heat-resistant beaker is safer than a test tube, but it may be harder to have this heated evenly.

chornedsnorkack - 1-7-2020 at 03:22

Quote: Originally posted by woelen  

The reaction which occurs first is formation of HClO3, which immediately disproportionates into HClO4 and ClO2 (and also some Cl2, O2 and H2O). The ClO2 gives the red/brown color in the liquid and also is the intense yellow gas above the liquid. It is extremely unstable and easily explodes. The HClO4 also is very dangerous, because here, it is more or less anhydrous and this is a very reactive and dangerous compound, which ignites and frequently explodes in contact with organics like paper, sugar, cotton, human skin and human hair.

HClO4 in concentrated H2SO4 is anhydrous and reactive, but it is not concentrated, because the concentrated H2SO4 is a non-explosive diluent. Unlike HMnO4, HClO4 seems to be miscible in concentrated H2SO4 and not liable to separate and explode. You would need to distil off HClO4 from the H2SO4 to get concentrated/explosive concentrations. Or add organics to produce immiscible/explosive perchlorates.

woelen - 1-7-2020 at 05:01

My experience is different. I once did the experiment and added a little piece of paper to the orange/red liquid, which I obtained from the H2SO4/KClO3-mix. The paper ignited, as soon as it touched the liquid and immediately after that, the mix exploded. It was only a little amount (a small spatula of solid KClO3 to which two or three drops of conc. H2SO4 were added), so there was only limited damage, just many tiny droplets sprayed around, which made tiny black spots on the wall and in my clothes.

chornedsnorkack - 1-7-2020 at 07:11

Quote: Originally posted by woelen  
My experience is different. I once did the experiment and added a little piece of paper to the orange/red liquid, which I obtained from the H2SO4/KClO3-mix. The paper ignited, as soon as it touched the liquid and immediately after that, the mix exploded. It was only a little amount (a small spatula of solid KClO3 to which two or three drops of conc. H2SO4 were added), so there was only limited damage, just many tiny droplets sprayed around, which made tiny black spots on the wall and in my clothes.


Yes, but what you did was add "a few" drops of H2SO4 to excess of KClO3. Which exactly gives you concentrated HClO4, explosive itself and especially with the dissolved ClO2.
What the OP did, using also small amount of KClO3 but rather more H2SO4, could precisely make the resulting mix more dilute and less explosive.
Another idea proposed above that sounds sensible is allow the orange liquid to stand to evaporate the most explosive chlorine dioxide. Or maybe blow through air, to speed up?
As for forcing chloric acid to dismute: chloric acid is described as stable to concentration of 30 %, but unstable above - can be brougt to 40 % with vacuum evaporation in cold, but not more.
If so, then chlorates should dismute not only in 95% sulphuric acid, but also in 50...80 % sulphuric acid. Giving dilute and therefore safe perchloric acid... though mixed with H2SO4 and K2SO4.

Bezaleel - 3-7-2020 at 06:36

Quote: Originally posted by chornedsnorkack  
Quote: Originally posted by woelen  
My experience is different. I once did the experiment and added a little piece of paper to the orange/red liquid, which I obtained from the H2SO4/KClO3-mix. The paper ignited, as soon as it touched the liquid and immediately after that, the mix exploded. It was only a little amount (a small spatula of solid KClO3 to which two or three drops of conc. H2SO4 were added), so there was only limited damage, just many tiny droplets sprayed around, which made tiny black spots on the wall and in my clothes.


Yes, but what you did was add "a few" drops of H2SO4 to excess of KClO3. Which exactly gives you concentrated HClO4, explosive itself and especially with the dissolved ClO2.
What the OP did, using also small amount of KClO3 but rather more H2SO4, could precisely make the resulting mix more dilute and less explosive.
Another idea proposed above that sounds sensible is allow the orange liquid to stand to evaporate the most explosive chlorine dioxide. Or maybe blow through air, to speed up?
As for forcing chloric acid to dismute: chloric acid is described as stable to concentration of 30 %, but unstable above - can be brougt to 40 % with vacuum evaporation in cold, but not more.
If so, then chlorates should dismute not only in 95% sulphuric acid, but also in 50...80 % sulphuric acid. Giving dilute and therefore safe perchloric acid... though mixed with H2SO4 and K2SO4.

Brauer statues that a "safer" way to generate ClO2 is by addding oxalic acid to the chlorate mixture. This generates CO2, which reduces the explosiveness of concentrated ClO2.
Quote: Originally posted by Formatik  
(...)
There is quite a bit of info on ClO2 in Gmelin's Handbuch. This is the most convenient resource for me. It's very condensed and gives me usually what I'm are looking for. In concentrated form, ClO2 is extremely dangerous to handle. In dilute form (like around 10%), it is fairly harmless. ClO2 has triggers, especially relevant to concentrated forms. Triggers like heat, light (diffused daylight or sunlight), shock, and oxidizables (organics, cork, rubber, etc). Also been mentioned a bit on this forum before.

Formatik, I'm looking for the text on ClO2 in Gmelin's, but the libraries are not accessible due the the Corona crisis. Do you maybe have it available?

woelen - 3-7-2020 at 13:41

It might be that dilution in a lot of sulfuric acid makes the mix less explosive. The OP used 1 gram of KClO4 in 4 ml of acid. I still think this is quite concentrated.

HClO3 is stable up to appr. 30% in water. In H2SO4 I expect it to be less stable. Stability of HClO3 in water is because it is a strong acid and it ionizes as H(+) and ClO3(-). The ClO3(-) ion is stable, while the covalent HClO3 is unstable. This effect also exists for HClO4. The undissociated acid is very unstable and reactive, while the dissociated acid, which forms ClO4(-) ions is remarkably inert. In water, HClO4 is completely ionized up to appr. 70% concentration (it is a very strong acid), and hence up to that concentration, the acid is quite inert. Again, in conc. H2SO4 I expect it to be much less stable, even at low concentrations.

What I found in another experiment, is that the cationic species ClO2(+) is more stable than HClO3:

https://woelen.homescience.net/science/chem/exps/chloryl/

The cationic species ClO2(+) is bright red, the decomposing HClO3 gives a more orange/brown color. The latter is due to ClO2 in solution. The brown/orange liquid gives off intense yellow ClO2 gas.

All in all interesting stuff and good to investigate it, but one must always be very careful with this kind of energetic compounds. An accident never is far away!

chornedsnorkack - 4-7-2020 at 02:32

When you consider using strong sulphuric acid, look at its Hammett acidity function:
https://macsphere.mcmaster.ca/bitstream/11375/19972/1/Peel_T...
Under 100 % is in Table X, page 80:
-10,02 at 96,0 %
-11,05 at 99,4 %
-11,93 at 100,0 %
Oleum is in Table XIX, page 97 (in mole %):
-13,02 at 10 %
-13,99 at 35 %
-14,96 at 75 %