peroxysulfuric acid - Archive File

[megalomania]

-¥§ ßØ(V)ßZ §¥-
New Member
Posts: 2
From:
Registered: JUL 2001
posted 07-09-2001 04:31 AM
--------------------------------------------------------------------------------
Hello all! I know that you frown on having new members post new topics, but I feel this is interesting enough to merit it, and I wasn't able to find any mentions of this compound earlier.
Do any of you here have any knowledge relating to peroxysulfuric acid, also known as caro's acid or pirahna fluid? I originally came across this in the explosives newsgroups. It was described as being one of the very strongest acids that you can get, and 'it can remove skin as fast as a knife' according to the member posting information on it. In addition to that, it can also dissolve glass and diamond [!]. This sounds very fascinating, as you could wreak some serious damage with a chem this dangerous. However, very little info can be found out there on it via google. About all i could find is that it is used in etching metals and glass as a dilute agent. Basically, what it is is H2SO5, formed by adding concentrated H2O2 to H2SO4.
H2SO4 + H2O2 -->H2SO5 + H2O

So in that regards it would be very easy to make, but I have no idea if you could concentrate it by boiling, if that would even be possible as it will dissolve glass. I couldn't find any info saying whether or not it could dissolve ceramic or teflon tho. If anyone out there cares to try to make it, go right ahead. Or even better, if you have some info on caro's acid, any help would be appreciated!


deezs
Frequent Poster
Posts: 113
From: Hungary
Registered: MAY 2001
posted 07-09-2001 01:05 PM
--------------------------------------------------------------------------------
As far as I know, the strongest acid is a mixture of HF and Sb(F)x. A well known hungarian chemist kills his time playing with this stuff. It dissolves wax too!
Caro's acid is a very strong oxidizing agent. Perhaps too strong. I belive, that it reacts wit diamond. Diamond is just carbon, it can be lighted with a special mirror. I think caro's acid is so strong, that it has no practical use. You can not mix it with any reducting agent.
Dissollving glass? I think glass can not be oxidized.
I have found a few words about it's manufacture:
- H2O2 + ccH2SO4
- H2O2 + HSO3Cl
- hydrolisis of H2S2O6 with H2SO4
Before you try to make it, search for detailed recipe.
------------------
"Don't belive anything, just because there is a good proverb for it."



a_bab
Frequent Poster
Posts: 55
From: doesn't matter
Registered: MAY 2001
posted 07-09-2001 03:46 PM
--------------------------------------------------------------------------------
I readed once about this strange acid, and all I remember is that it is a VERY corosive substance, obtained from 98% sulfuric acid and 30 % (minimum) hydrogen peroxide, and a little experiment with it : if you drop a match (wood type), or a piece of wood (a splinter) in it, it will vanish is seconds !
The pyranha solution is obtained from
K2Cr2O7 and sulfuric acid, and is used for cleaning the lab vessels (glass). It is werred off when the colour is changed from orange to green (the Cr ions are reduced)

Your H2O2/H2SO4 mix won't corrode glass (at normal temperature only HF, some F compounds and some hydroxides can).

P.S. For God sake, change your username !
________________________
http://move.to/pyromania




simply RED
Frequent Poster
Posts: 242
From: HELL
Registered: OCT 2000
posted 07-09-2001 08:26 PM
--------------------------------------------------------------------------------
Is its formula : H-O-O-(SO2)-O-H?
I read aboutthe existance of HClO5...which is also a peroxyacid. I don't have info on these acids...



-¥§ ßØ(V)ßZ §¥-
New Member
Posts: 2
From:
Registered: JUL 2001
posted 07-10-2001 03:45 AM
--------------------------------------------------------------------------------
Next off, thx for your info about caro's acid. I was not able to locate any decent info on it anywhere, so what I know only comes secondhand from a chemist on the alt.engr.explosives newsgroup, so I do trust his imput. I'm going to get some h2o2 tomorrow, so I'll boil that down and try to make some caro's acid, and i'll report back the results.
BTW, does anyone know the temperature that h2o2 decomposes? the best that I could find last nite was the heat of decomposition, how much energy it releases. But it appears that you can at least heat it to the boiling temp at 1atm before it will decompose. And lastly, if anyone knows what concentration you can reach by boiling h2o2, that would be very appreciated. I was under the impression it was around 60ish, but I couldn't tell you the source of this info.

Thx all!

------------------
-----
oh shit, you mean it's lit?



Rhadon
Frequent Poster
Posts: 95
From: Germany
Registered: OCT 2000
posted 07-13-2001 07:39 PM
--------------------------------------------------------------------------------
Deezs: As far as I know HClO4 is the strongest acid that exists.
-¥§ ßØ(V)ßZ §¥-: To mention a way how to synthesize Caro's acid: KHSO5 und K2SO4 are added to H2SO4. Another method: Adding H2O2 to chlorosulfuric acid. I doubt that adding H2O2 to H2SO4 will work, but just try it out and tell us what you found out. If you're well-equipped you can try if the resulting acid oxidizes aniline to nitrobenzene (H2SO5 does so).
Though, boiling down hydrogen peroxide will not work, most of it will just decompose.

[Marvin]

Deezs was describing a 'super acid' far superior to perchloric in terms of [H+], though I dont know if they have any uses.

Adding sulphuric acid to barium peroxide to produce dilute hydrogen peroxide, and then boilng gently in a scratch free container until it starts to decompose is supposed to produce approx a 40% solution. The stabilisers in commertial stuff may or may not help. Ive produced something over 30% by heating 9% to a little below boiling and directing a fan onto the surface. The fumes were more than a little unpleasent but I got what I wanted somewhere between a 3:1 and a 4:1 reduction in volume.

Pure 40% can be furthur concentrated up to 99+% as is needed by leaving the solution over sulphuric acid in a vacuum dessicator at RT. More peroxide will be lost per amount of water as the concentration rises, and all impurities remain to contaminate the product. Much more of a problem with stabilised dilute solutions. There is aparently no eutectic for this method.

[drednort]

Caro's acid (H2SO5) is pretty aggressive and is a better oxidiser than H2SO4 from which it is derived. Not enough to dissolve glass, but maybe to damage the surface upon long exposure (HF although not a strong acid corrodes glass very easily). I use it sometimes (in small amounts) for cleaning up particularly dirty glassware. Either use Caro or fuming nitric. I've never heard or read of anyone concentrating it. I would guess that it is not so stable in pure form so concentration would probably give degradation.
K2Cr2O7 and sulfuric acid (i.e. "Chromic Acid") is also a good oxidising acid. This acid is stable but I've seen an accident with this, in which it was being stored in a sealed container. It developed pressure (somehow) and the guy who tried to open it took a hit from the shattering vessel.