# Caro acid



## OMG (Jun 17, 2008)

Does anyone know if Caro acid would be strong enough to oxidize sulfides into the metal and SO2? I tried using hot concentrated sulfuric, but that didn't work as well as I'd hoped.


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## OMG (Jun 17, 2008)

Also, if caro acid can oxidize carbon, would it be able to oxidize gold?


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## Noxx (Jun 17, 2008)

Caro acid ?? What is it ?

What's the chemical formula ?


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## Oz (Jun 17, 2008)

H2SO5 = Caro’s Acid

If you have H2S2O8 (persulfuric acid) and add water you will get Caro’s Acid like this…
H2S2O8 + H2O = H2SO5 + H2SO4 

This is not something I am sure of but I was recently reading about it. Please someone correct me if my information is wrong.


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## OMG (Jun 17, 2008)

Add H202 to H2SO4.
Be very careful. Its very oxidizing. And adding the h2o2 usually involves adding water, so if the sulfuric is concentrated, it heats up very quickly.
If you spill this on organics, it may start them on fire. So it would really suck if you spilt it on yourself.
I was reading it is strong enough to dissolve carbon!

I read another way to make it is add O3 to concentrated sulfuric. That way you aren't adding water to the acid, and it won't heat up as much.


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## OMG (Jul 25, 2008)

I've also found it does dissolve pyrites, and is supposed to dissolve all sulfides.


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## arthur kierski (Jul 26, 2008)

omg--this is a very interesting information
could you give us some more information on dissolution of pyrites and carbon with caros acid? 
thanks arthur


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## OMG (Jul 26, 2008)

There was a google book I saw the chemical reaction in (for sulfides to sulfates), but I don't remember how much information was there. I tried to find the book again, but couldn't. I will keep searching. Let me know if you find any good info as well.
Search:
Caro's acid
Piranha solution
Peroxymonosulfuric acid
Persulfuric acid
Peroxysulfuric acid

All I can say for dissolving pyrites is from what I've done. I made up a small amount of caro's acid using 500ml of 80% H2SO4, and maybe 100ml of 3% H2O2, (heated to about 75 C) and put in some pyrite and chalcopyrite riddled rocks and it reacted vigorously, and dissolved and broke apart one of the rocks. It took most of the color out of the rocks as well.
Other than saying that it seems to work quickly, that's all I can say.


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## Anonymous (Jul 28, 2008)

OMG said:


> Also, if caro acid can oxidize carbon, would it be able to oxidize gold?



Sounds like there are "cheaper" and "safer" alternatives to this flash flesh fire compound your talking about.

on the level of hobbyist why would you want that type of risk?


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## OMG (Jul 28, 2008)

jdwisnie,
I'm experimenting and gathering data mainly.

Caro's acid/Sulfuric acid mix is attractive because it will dissolve most base metals as well as sulfides. Sulfuric acid is the cheapest usable acid I know about, as well, the caro's part of it can be (re)generated by electrolysis of the solution. Also... I think it would be easier to regenerate the spent acid as well.
Caro's acid is very powerful, but if I decide to use it, I will be only making enough of it to do its job (possibly even making it using electrolysis right in the tank where it will be used), at which point it is used up and is no longer caro's acid, just metal sulfates.

Also, on another note, I'm looking into it as a method to produce ozone in enough quantity so I can try to oxidize ammonia to make my own nitrates.

All this experimenting and stuff is my hobby, I've found that I enjoy learning chemistry quite a bit. (much more than back in high school). Once I learn enough I will start refining (maybe even as a source of income).


BTW,
Reading says that gold is not oxidized by caro's acid. But I would definitely have to test that out because H2O2 oxidizes gold enough to dissolve it, and caro's acid is just sulfuric and h2o2.


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## jsargent (Nov 1, 2008)

OMG said:


> jdwisnie,
> I'm experimenting and gathering data mainly.
> 
> Caro's acid/Sulfuric acid mix is attractive because it will dissolve most base metals as well as sulfides. Sulfuric acid is the cheapest usable acid I know about, as well, the caro's part of it can be (re)generated by electrolysis of the solution. Also... I think it would be easier to regenerate the spent acid as well.
> ...



Caro's acid,(or peroxy monopersulfate, the potassium salt of it) WILL dissolve gold if your leach solution has sodium chloride or sodium bromide in it. Copious amounts of chlorine/bromine is produced forming gold halide. According to the literature, however if your ORP is too high (too oxidizing) then a layer of gold oxide will passivate the gold and prevent further dissolution. Shoot for 850mv and a pH of <3.8 
Also, forget about using stainless steel anywhere in this. Eats it right up.


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## DaniH (Nov 29, 2021)

jsargent said:


> Caro's acid,(or peroxy monopersulfate, the potassium salt of it) WILL dissolve gold if your leach solution has sodium chloride or sodium bromide in it. Copious amounts of chlorine/bromine is produced forming gold halide. According to the literature, however if your ORP is too high (too oxidizing) then a layer of gold oxide will passivate the gold and prevent further dissolution. Shoot for 850mv and a pH of <3.8
> Also, forget about using stainless steel anywhere in this. Eats it right up.


How you stable ph at 3+ while having orp more than 800mv?


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## Lino1406 (Nov 30, 2021)

To convert sulfide to sulphate, H2O2 20% does that, no need for H2SO5


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