Question concerning the History of the AP process,..

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Anonymous

Guest
Hello All,

I have been reading Hoke and lurking the forum, learning so much!
Many thanks to everyone! :)
Does anyone know the history of the Acid-Peroxide process, when it was invented and by whom?
Hoke doesn't mention it,...anyone know?

Thanks so much,
FB
 
Hoke doesn't mention it because, in her day, just as in my day, nitric acid was readily available, so there was no need.

Steve may well be the one that can answer your question about who "invented" the idea, but it's just fundamental chemistry for those that understand it well.

Harold
 
Freaky,

My experience with using the AP process came about from a personal quest to find a suitable replacement for dissolving base metals without the need for nitric acid. I did not 'invent' the process more as Harold points out, it was a matter of Chemistry for me.

Since my discovery of the usefulness of the AP process I guess I can claim that I have contributed to the popularization of the process here on the forum.

Some time after I had experimentally determined the correct ratios for the mix I happened across documents which supported my find. I have also run upon mention of similar processes in several literary works printed prior to my work. Come to find out the AP process is actually claimed to be used at some large scale refineries.

As with any chemical process, they have all been around since chemicals came into existence, it's just a matter of who stumbles across them and formulates an application for a given reaction and then utilizes what they have discovered.

I'm 100% sure there are many 'undiscovered' processes of base and precious metal dissolutions. Most guys and girls just don't have the creative drive or chemical background to calculate and test their calculations with real life experiments to find these processes. It's much easier for most folks to wait around for someone else to do the ground work for them.

Steve
 
Although the basics have been known, I think Steve deserves about 95% of the credit for advancing both the AP and AC processes to a point that no one else in history has.

Come to find out the AP process is actually claimed to be used at some large scale refineries

Steve, do you have more data on this - or, your original source for your statement? Seems iffy, to me, but there could have been some isolated usage, I guess. Have you yet thought of an economical, efficient, fast way to use either of them on a grand scale? You could very well be on that threshold.
 
I've been trying out a hybrid process that starts as AP, then Hypochlorite is added to use up the HCl, generating Chlorine and also begins raising the Ph of the solution. The finished liquor is mildly acidic with HCl.
 
Noxx said:
And it work ?

The thing is, it seems to used a lot of chemicals...

But it's interesting...

AP works best when the HCl is concentrated, but as the HCl is used up and diluted by additions of Peroxide, the reaction rate slows down. Adding Hypochlorite generates chlorine which is more agressive than AP and only uses up the residual HCl that's already in solution.

HCl/Cl works best in dilute solution because of the limited ability of water to absorb Chlorine. I found that using con HCl with Hypochlorite tends to react vigorously, especially when warm and much of the Chlorine is lost. This is ok if all you want to do is generate Chlorine to precipitate Palladium, but for digestion, it works better cool and dilute.

It's a work in progress. I can't see where it would cause any problems.
 
Acid with strong enough peroxide will liberate chlorine itself. That is why to a certain extent, bleach with acid is relatively similar, as it also liberates chlorine since hypochlorite is unstable in acidic conditions.


HCl-peroxide has long been known as an effective method for dissolutions and etching, particularly with the refractory metals.
 
You're right about the similarity of the process. I think the HCl/Cl via Hypochlorite is a bit cheaper than using peroxide.

I'm just trying to use everything but the squeal. There's nothing wrong with Acid/Peroxide.

A penny saved is a penny earned.
 
GSP said:
Steve, do you have more data on this - or, your original source for your statement? Seems iffy, to me, but there could have been some isolated usage, I guess. Have you yet thought of an economical, efficient, fast way to use either of them on a grand scale? You could very well be on that threshold.

Chris,

I was using AP and HCl-Cl long before I realized it was used in bigger refineries as I have mentioned.

Here's the reference for my statement:

Small Scale Refining of Jewelers Wastes by Roland Loewen pg.175-176 C1995 said:
Hydrogen Peroxide and hydrochloric acid will dissolve gold. This is used in several refineries. One refiner reported that the recovery of PGMs was much improved when hydrogen peroxide rather than nitric acid was the oxidizer. The known affinity of platinum and palladium for nitrogen compounds make this a believable conclusion. Unless extended boiling of solutions to remove nitrogen compounds is done it is quite possible that some forms of nitrogen could combine and hold PGMs.

We have no experience with hydrogen peroxide oxidation. The use of the 50% grade is reported. We speculate that the metal is in hydrochloric acid solution and is treated by adding the H2O2. Because hydrogen peroxide is an unstable material considerable care in its use is needed. The stream of peroxide should not be introduced under the solution because of the chance of draw back to the supply tank. There the metals present will likely catalyze peroxide decomposition which can be explosive.

Hydrogen peroxide is a very reactive chemical. It also decomposes and a product of decomposition is a gas (oxygen). In low concentration and with a stabilizer this decomposition is slow. At high concentrations and/or in the presence of a catalyst (many metals are such catalyst) this decomposition goes at explosive rates. Damage can be severe.

A through education in the characteristics of hydrogen peroxide must proceed any work with this material. The manufacturers of hydrogen peroxide can usually give considerable information and advice.

The dissolution reaction is probably :

2Au + 3H2O2 + 6HCl = 2AuCl3 + 6H2O

I have also found this same formula in several texts.

What is odd to me about his mention of the use of peroxide is his lack of references cited on the source of the material. He has references throughout the book (just about every paragraph) on many subjects, but not this one. Just above this section he mentions HCl and Chlorine gas without reference also.

I experimentally stumbled across the use of AP for stripping base metals around three years ago. I've owned this book for less than a year. I used AP to dissolve my first batch of monolithic capacitors around two years ago. The 3% stuff is super slow, but it works very well on Palaldium. I reallly dislike evaporating nitric acid based PGM solutions. With AP this problem is solved.

As for up scaling the reaction, yes. I have penciled out a contraption to use AP in a continuous configuration which works with circulating pumps, filters, and electrolytic reactions. Theoretically you can electrolytically rejuvenate the AP as it's saturated and recover the copper moss, returning the rejuvenated solution to the reaction vessel. In essence you can dissolve pounds of copper based pins in a very short time and retrieve the gold foils when the copper is gone. The copper ends up in a separate bucket in mossy form.

I built a prototype and turned it on, but the spent AP I used was too saturated when I first started the device :oops: . Huge amounts of chlorine gas were evolved in just a few seconds of operation. Ideally you would start with a fresh solution and turn on the electrolytic cell to maintain the proper CuCl2 concentration to affect rapid dissolution while plating out the dissolved copper.


Steve
 
I use that in the lab for cleaning. Ammonium persulfate and concentrated sulfuric acid form something like a milder version of Caro's acid/peroxymonosulfuric acid.
 
Check out this free pdf download: 'Applications of Hydrogen Peroxide and Derivatives' which I came across yesterday in my travels. It just may answer everyone's questions....or not.

http://tinyurl.com/2fdw5w

Shaul
 
Hello Lou,
I can think of Perulphate + Sulphuric + H2O2
as a cleaner of course, but what I meant is a
replacement for the other AP process
with (possibly) the following advantages:
1)Less gold dissolution with the absence of Cl- ion
2)Should work on nickel too
3)No smell of chlorine
3)In comparison to another "bathroom process" -
FeCl3/H2O2, quicker and not giving the
nasty Fe sludge
 
Lino1406 said:
Hello Lou,
I can think of Perulphate + Sulphuric + H2O2
as a cleaner of course, but what I meant is a
replacement for the other AP process
with (possibly) the following advantages:
1)Less gold dissolution with the absence of Cl- ion
2)Should work on nickel too
3)No smell of chlorine
3)In comparison to another "bathroom process" -
FeCl3/H2O2, quicker and not giving the
nasty Fe sludge

I've been using H2SO4/H2O2 for a while and I prefer it for stripping base metals because it doesn't fume and the H2O2 can be rejuvinated through electrolysis. In th old days, H2O2 was manufactured by the electrolysis of dilute H2SO4.
It's very agressive, I've even made Rhodium Sulfate with it (from the hydroxide).
 
I have tried Irons suggestion of washing my Gold precip with dilute sulfuric acid, several times, instead of HCl.

It works very well in removing the last traces of tin and copper salts, but most of all I`ve noticed it also reduces the electro-static repulsion of the
Gold particles of the precip, so that the precip becomes more cohesive and collects easily in a corner of the beaker.

It then is very easy to move it where you want, with a wash bottle.

Al
 
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