Some advice on removing base metals?

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Z

zorba

Active member
Joined
Feb 5, 2010
Messages
33
Location
Sweden
I have all these old CPU:s, pins e.t.c laying around in my basement.
I am familiar with most of the precipitation methods, separations and so forth.
Now my question is what is the best method when removing the base metals, primarly copper ? Would it be soaking them in some nitric?
I appreciate some advice on this. And is it possible to have the collection of gold and copper sand together when burning it into a dot and during the process heating it over the coppers evaporation degree so that the copper evaporates leaving the gold behind?
 
Suggested reading, Hokes, Refining Precious Metals Wastes - you will find it on the forum.
 
gustavus said:
Suggested reading, Hokes, Refining Precious Metals Wastes - you will find it on the forum.
Click to expand...

Thanks for the reply, i have read a bit of her master piece but i cant find her instructions on separatating the copper from the gold.
What page was it if you recall?
 
The Hoke book is mainly involved with jewelry scrap and wastes. The reason it is recommended is that she provides the best basic (but, detailed) information on the reactions of the various chemicals on various metals. If you are doing jewelry scrap, the info is step-by-step, in detail. The Hoke book is written very simply and she writes in such a way that is very easy for the layman to understand.

You will find that there is almost no information on electronic scrap (after all, the book was written in 1940). The best info on the planet in dealing with electronic scrap is found on this forum. However, the Hoke book will give you a better understanding of most all the processes on the forum. No matter what you want to do, the Hoke book is the best place to start.

As far as separating gold from copper goes, you basically have 3 options:

(1) Selectively dissolve the copper without dissolving the gold. This can be done with nitric acid or by using the muriatic acid/hydrogen peroxide method as developed by Lazersteve. There are tons of very detailed information on the forum for both processes.

(2) Selectively remove the gold without dissolving the copper. This can be done by using the electrolytic sulfuric acid stripper. Here again, there is tons of information on the forum about this.

(3) Dissolve everything and selectively precipitate the gold. This can be done with aqua regia (a combination of muriatic and nitric acids) but, unless the gold makes up a major portion of the material, this is not the way to go, for a number of reasons. With most gold plated electronic materials, such as fingers, this is almost never the way to go. With certain types of old CPUs that contain gold brazes, however, this may be the best method.

Read Hoke, search and read the forum, and watch the videos on Lazersteve's website.
http://goldrecovery.us/
 
goldsilverpro said:
The Hoke book is mainly involved with jewelry scrap and wastes. The reason it is recommended is that she provides the best basic (but, detailed) information on the reactions of the various chemicals on various metals. If you are doing jewelry scrap, the info is step-by-step, in detail. The Hoke book is written very simply and she writes in such a way that is very easy for the layman to understand.

You will find that there is almost no information on electronic scrap (after all, the book was written in 1940). The best info on the planet in dealing with electronic scrap is found on this forum. However, the Hoke book will give you a better understanding of most all the processes on the forum. No matter what you want to do, the Hoke book is the best place to start.

As far as separating gold from copper goes, you basically have 3 options:

(1) Selectively dissolve the copper without dissolving the gold. This can be done with nitric acid or by using the muriatic acid/hydrogen peroxide method as developed by Lazersteve. There are tons of very detailed information on the forum for both processes.

(2) Selectively remove the gold without dissolving the copper. This can be done by using the electrolytic sulfuric acid stripper. Here again, there is tons of information on the forum about this.

(3) Dissolve everything and selectively precipitate the gold. This can be done with aqua regia (a combination of muriatic and nitric acids) but, unless the gold makes up a major portion of the material, this is not the way to go, for a number of reasons. With most gold plated electronic materials, such as fingers, this is almost never the way to go. With certain types of old CPUs that contain gold brazes, however, this may be the best method.

Read Hoke, search and read the forum, and watch the videos on Lazersteve's website.
http://goldrecovery.us/
Click to expand...


Very well put goldsilverpro, i am actually acquainted with many of the above mentioned processes. I have been reading a lot on this and have tried some myself, but i have not yet reached the meaningful points and because of the fact that i am a newbie to this i have done many faults while working.
If it werent for this excellent forum and books by Hoke and Ammen i would have given up on the refining business a long time ago.

So just one quick question, if i have my gold and copper assay (containing some other base metals aswell) in the form of sand, were i have precipitated it through electrolysis, is it possible that i could now treat it with some nitric to dissolve the base metals and the gold will then be left as a brown powder? (And later on maybe dissolve the gold itself in AR to purify the gold).

The reason why i am asking and not trying it myself is the knowledge which i do not have on this subject and you surely have. And also the fact that i must think cheap and not waste the little nitric i make for myself.. Moreover, Hoke only indicates how to treat the assay when it is in the form of a button, so i doubt it myself but is there any difference when it is not in that form?
 
So just one quick question, if i have my gold and copper assay (containing some other base metals aswell) in the form of sand, were i have precipitated it through electrolysis, is it possible that i could now treat it with some nitric to dissolve the base metals and the gold will then be left as a brown powder? (And later on maybe dissolve the gold itself in AR to purify the gold).
Click to expand...
Sure. Just make sure that all the chlorides (if that's what you used in the electrolysis) have been rinsed out very well before using the nitric. Otherwise, you could form some aqua regia and dissolve some of the gold. I would probably use hot distilled water for the final rinse or two.

What do you mean when you use the term "assay"?
 
zorba said:
And is it possible to have the collection of gold and copper sand together when burning it into a dot and during the process heating it over the coppers evaporation degree so that the copper evaporates leaving the gold behind?
Click to expand...
What you propose is not viable. When you heat gold to the point of melting, any base metals contained within tend to oxidize. While you may drive some, at least partially, from the gold, the net result is gold of poor quality due to entrapped oxidized base metals. An exception to that concept is if chlorine is introduced to the molten mass, which systematically expels elements. The process is well documented (Miller chlorine process) and beyond the scope of the home refiner.

Harold
 
Maybe a bit off the topic, i just wonder if there is anything wrong with my concentrated sulphuric acid which has a yellowish almoust orange colour?
I took the acid from a car battery and boiled the water in 150-200 celsius for about 30 minutes. Now it has taken this colour, is that normal ?
 
Harold_V said:
zorba said:
And is it possible to have the collection of gold and copper sand together when burning it into a dot and during the process heating it over the coppers evaporation degree so that the copper evaporates leaving the gold behind?
Click to expand...
What you propose is not viable. When you heat gold to the point of melting, any base metals contained within tend to oxidize. While you may drive some, at least partially, from the gold, the net result is gold of poor quality due to entrapped oxidized base metals. An exception to that concept is if chlorine is introduced to the molten mass, which systematically expels elements. The process is well documented (Miller chlorine process) and beyond the scope of the home refiner.

Harold
Click to expand...


Right, as i thought it is almoust impossible for a home refiner to do such.
Great explanation thanks.
 
zorba said:
Maybe a bit off the topic, i just wonder if there is anything wrong with my concentrated sulphuric acid which has a yellowish almoust orange colour?
I took the acid from a car battery and boiled the water in 150-200 celsius for about 30 minutes. Now it has taken this colour, is that normal ?
Click to expand...

Crystal clear new battery acid can turn an amber color when concentrated.
 
When removing base metals with nitric acid, is it essential for the nitric to be diluted with one part water (according to Steves recipe in the GRF Handbook) if the nitric is approximately ~50 % due to being homemade ? Or should it only be diluted when having the 70 % nitric?
 
Diluting 70% nitric plus an equal volume of water makes twice the volume of 35% nitric.

Considering the expense of store bought nitric acid, and the time required to make your own, be sure to dilute the acid to 35% (or even less will work, but slower). The water acts as a medium for the metal nitrates to dissolve into. This is also another reason to add your nitric in controlled doses, and to know how much nitric to use in advance of performing the reaction.

Imagine it like 70% HNO3 is a room nearly packed full with 70 people in it, while 70% HNO3 with an equal volume of water added to it is the same number of people, but the room is now twice the size of the first room. The first room will hold only a few more people, but the second room will hold more than 70 additional people. Of course, those people must be soluble in water to fit in the additional space provided by the added water! :mrgreen:

Steve
 
Unless you get nitric very cheaply it is also of benefit diluting it to 35% because some of the red nitric gases are re-absorbed into the water to perform a repeat performance in digesting your metals.

A bit more bang for your buck.
 
I've never tried to hide my lack of education, especially where chemistry is concerned, but one of the things I did when I refined is take a quarter of chemistry at the community college, near my home at the time. In it there was discussion of the hydronium ion-----which raises my question. How much does it enter in to the equation where nitric acid is concerned? I was lead to believe that the addition of water provided an extended amount of work by a given lot of acid. It's clear that water should be added to concentrated nitric when silver is dissolved----the question is, does it actually do more work? If so, what, exactly, is the mechanism by which the additional work is provided. Regenerating from the fumes sounds like part of the process. Is there more?

Harold
 
As you know Harold, I am no chemist. What I speak of is predominately empirical in nature. One thing going for dilution with water is also the solubility curve of some base metals we are trying to remove. Most have witnessed driving a reaction with heat to get the most out of an acid only to find a crystalline mass upon cooling. How do we fix that? We add water, and perhaps some heat to speed things along. When was the last time anyone found that the best way to solve that problem was to add more acid instead of water.

When I am digesting platinum I usually use an erlenmeyer flask with a glass funnel in the mouth. Due to the long digestion times with platinum I find it advantageous to reduce evaporation while under heat as well as the added benefit of condensing the NOX fumes back into solution.
 
lazersteve said:
Considering the expense of store bought nitric acid, and the time required to make your own, be sure to dilute the acid to 35% (or even less will work, but slower). The water acts as a medium for the metal nitrates to dissolve into. This is also another reason to add your nitric in controlled doses, and to know how much nitric to use in advance of performing the reaction.
Click to expand...

Alright, that cleared my foggy mind up a bit... Apparently, the water also helps as a solvent to the base metals.
So lats say that i have a ~50% nitric which i dilute one part down to 25%, will it still have an effect when dissolving
copper and silver from the already precipitated brown gold sand?

Imagine it like 70% HNO3 is a room nearly packed full with 70 people in it, while 70% HNO3 with an equal volume of water added to it is the same number of people, but the room is now twice the size of the first room. The first room will hold only a few more people, but the second room will hold more than 70 additional people. Of course, those people must be soluble in water to fit in the additional space provided by the added water! :mrgreen:

Steve
Click to expand...

Nice metaphor when explaining. :lol:
Thanks Steve !
 
Harold, I have read a little bit on H20 and acids or bases, and how water is such a strange chemical, can be acidic or basic easily, and about the Hydronium ion, Hydrogen positive, and hydroxide negative.

reading this has confused me also, but I think you have a point about its effect on the acids ability to consume metals into solution.




I would also be interested to learn more about this subject.
 

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