Refining Pentium Pro with AR

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Metaphore

Well-known member
Joined
Sep 19, 2014
Messages
55
I've successfully used AR for recovery of gold foils as well as black powder from a sulfuric cell. This time, decided to try a few Pentium Pros. It all started out well but after several hours on the hot plate and several additions of nitric, the solution stopped reacting to more nitric. At this point, the solution was VERY dark green. I poured it off and found that there is still plenty of gold left on the chips. Put it back on the plate and added more HCL, nothing. More nitric, nothing.

Please direct me to some information that may help me out of this.

Thanks!
 
Metaphore said:
I've successfully used AR for recovery of gold foils as well as black powder from a sulfuric cell. This time, decided to try a few Pentium Pros. It all started out well but after several hours on the hot plate and several additions of nitric, the solution stopped reacting to more nitric. At this point, the solution was VERY dark green. I poured it off and found that there is still plenty of gold left on the chips. Put it back on the plate and added more HCL, nothing. More nitric, nothing.

Please direct me to some information that may help me out of this.

Thanks!

You may need to expand your solution.

Scott
 
Could the gold be covered by a coating? Since gold will dissolve in nitric and HCL (and reportedly you have both in solution), then it is either covered with a coating, maybe isn't gold, or maybe it is just dissolving very slow. I may be wrong, but if so, please correct me.

Why not remove a few chips with the "gold" on them, rinse and put the chips into a new container with some HCL and a small amount of nitric let sit for about 30 seconds after mixing well, then take a drop and test with SnCl, heat, and test another drop 5 minutes later. If test shows darker result, then gold may still be dissolving.

Just a thought anyway.
 
Took a much closer look and shined a flash light through it. Close enough to get a tiny whiff through the respirator. Sucked. But I did see that there is a reaction. It's very slow and very hard to see in the extremely dark liquid.

The gold isn't covered, it's all exposed. I took the ceramic plates off with a blow torch and the rest are the pins and the top cover. When I drained the AR, I saw the top covers flaking and about 10% of the pins intact. I could also see some gold inside the processor, where the ceramic cover used to be. It was all exposed.

@NobleMetalWorks, what does expanding the solution mean?

Should I be concerned about the color of the solution? With the foils and black powder, my solution was a nice deep gold color. This one seems like it has a ton of copper in it. Will I need to do anything different with the AR to drop the gold?

Thanks!
 
I would think that when you were dissolving the foils and black powders, you were refining. When you are dissolving the gold and base metals as in your current situation, you are reclaiming. Therefore, you would have more base metals in solution since you chose to dissolve everything.

so after everything is dissolved, you will first have to get rid of the extra nitric, then drop the gold (probably more contaminants in this batch than in prior ones), then refine the dropped gold.
 
Metaphore said:
Took a much closer look and shined a flash light through it. Close enough to get a tiny whiff through the respirator. Sucked. But I did see that there is a reaction. It's very slow and very hard to see in the extremely dark liquid.

The gold isn't covered, it's all exposed. I took the ceramic plates off with a blow torch and the rest are the pins and the top cover. When I drained the AR, I saw the top covers flaking and about 10% of the pins intact. I could also see some gold inside the processor, where the ceramic cover used to be. It was all exposed.

@NobleMetalWorks, what does expanding the solution mean?

Should I be concerned about the color of the solution? With the foils and black powder, my solution was a nice deep gold color. This one seems like it has a ton of copper in it. Will I need to do anything different with the AR to drop the gold?

Thanks!

Your solution can only hold so much dissolved metal before it becomes exhausted. Metal is dissolved into solution according to the reactivity series: https://en.wikipedia.org/wiki/Reactivity_series. It seems your solution is pregnant with dissolved metals. When you add acid, it is most likely attacking the exposed metals under the gold plating and thus making it seem like your solution is no longer dissolving gold.

Think of it like this. You introduced many different types of metals into a solution of AR. The metals that are exposed are the first to dissolve into solution. Since you have gold plating that was covering base metals, the gold plating goes into solution until the base metal is exposed, then the AR solution attacks the base metals instead of the gold, you can refer to the reactivity series so that you might understand what I mean. The metals at the top of the scale I posted the link for, will dissolve into solution before the metals at the bottom. Once enough gold has been dissolved to expose the base metals to AR, the AR no longer attacks the gold, but rather the base metals. Until the base metals are completely dissolved, or you remove them, your AR solution will only slowly dissolve gold into solution.

This is one of the many reasons why it's better to remove the pieces that contain gold, from the ones that do not. As well, we try not to dissolve metals into solution that might cause issues in precipitation of the metals we are after. If for example the heat spreader of the CPU is made of Kovar, you are metals into your solution that you don't really want to deal with.

When a solution becomes saturated with base metals, it no longer can dissolve or hold in solution anymore metals. I would suggest removing those parts of the CPUs that still have gold on them, and dissolve in a new AR solution.

The heat spreader also has solder that might contain lead solder which could also cause problems and should be removed prior to precipitating gold.

When I made the suggestion to expand your solution, what I am meaning is to provide more room for metals to be dissolved into solution. You can expand a solution by adding more acids, or water or? All dependent upon what type of solution you have, and what your intent is. You expanded your solution when you added more acid, but as the acid was attacking the base metals instead of the gold, it seemed that your AR solution was not working, or working on slowly.

Hope this helps...

Scott

Scott
 
"Expand your solution"

This is just an extreme example and not meant as a method to follow by any means.

I may be wrong but I think he means you don't have enough total solution (AR) to hold all the metals you are trying to break down. An extreme example would be trying to process 100 of your Pentium Pros in an ounce of AR. We know that isn't likely to happen so you would need to expand your solution to a point that all 100 processors could be fully taken into the AR solution. This could mean that you may need 5 gallon of AR for the 100 processors instead of an ounce.

I see NobleMetalWorks beat me to it, but I will leave it anyway.
 
I think NobelMetalWorks is also saying that you could use the reactivity series in your favour. Initially some gold and base metals will go in solution and if you don't add nitric or hydrochloric acid the gold will be cemented out by the base metals, test with stannous chloride and if you don't have gold in solution you could use fresh AR. Basically it would remove most base metals first letting you reduce the gold from a cleaner solution.

Marco
 
I've had some experience with this.

I used nitric to try to dissolve the base metals in some gold filled eye glass springs, the pieces that loop around the back of your ear to hold the glasses on your face.

What I didn't know is that nitric acid is a bad choice for dissolving steel, it doesn't do it very well.

I should have used hydrochloric acid instead, it will dissolve iron (steel) much better than nitric acid will. In fact, concentrated nitric acid can be stored in stainless steel containers.

The spring steel had iron in it - you can test your dark green solution with ammonium or potassium thiocyanate, it will turn blood red if dissolved iron is present.

I knew I had gold foils, I could see them (what I didn't see, or recognize was that because dilute nitric doesn't dissolve steel very well, there were many pieces of steel in with the gold foils).

Not knowing any better, I drained off the dark green solution, added hydrochloric acid to the foils and then small amounts of nitric acid to form Aqua regia. The foils dissolved as expected.

I filtered the solids out of the solution and got a few pieces of spring steel with a bunch of brown powder I thought was dirt.

Then I did a stannous check of the filtered solution to verify that I had Gold in solution before I precipitated the gold with SMB.

I got real confused - the stannous test was NEGATIVE.

How could this be? The Gold foils were gone, dissolved by the Aqua regia, yet there was no gold in solution?

It turns out that the iron from the spring steel was cementing the gold out of solution as fast as it dissolved.

That brown powder in the filter that I THOUGHT was dirt was really the gold that had been cemented out by the pieces of steel! Good thing I save all my filters.

I Retrieved the filter with the brown powder and pieces of spring steel and put it into a beaker and dissolved it again with AR. This time everything went into solution. I did a stannous check and there was gold in solution, I precipitated and all went well from there.

The point is that if you have iron present in with your pregnant gold solution then the iron will cement out the gold as fast as the gold dissolves. AR will dissolve gold faster than it will dissolve iron so the iron will just sit there, immediately cementing out the gold as a brown powder just about as fast as the gold dissolves.

Another confusing aspect is that the iron will consume the acids so no more fumes will evolve. It looks like the reaction is done because the foils are gone and there are no more fumes. But what happens is the iron consumed the acids and cemented out the gold while being masked by the dark green solution so you can't tell what's going on inside the beaker!

If you keep adding fresh acids then the gold will finally go into solution and stay in solution once all the iron is dissolved.

This is why it is so important to understand the reactivity series of metals chart.

kadriver
 
Hi Can we get some perspective on this please as it would help with the answers?

How many Pentium Pro processors are you recovering from and what is the total volume of liquid in the original AR solution?
 
spaceships said:
Hi Can we get some perspective on this please as it would help with the answers?

How many Pentium Pro processors are you recovering from and what is the total volume of liquid in the original AR solution?

So long as the OP is adding Nitric acid, only as needed in order to dissolve all the gold into solution, I'm not sure that the quantity of CPUs matters so much. The only difference in quantity is the amount of acids required to dissolve the gold properly. This being said, the OP did say that it was "a few" Pentium Pros. I would wager this means around 2, but may mean a few more. I think after the OP reads what has been posted, he will be well on his way to resolving any issues.

Kadriver,

I wish there was a like button on this forum. Your posts are some of the best, not only because of the information you impart, but also your willingness to be utterly honest even to the point you express your own mistakes. You add value to the forum. I appreciate your posts!

Scott
 
I hear you Scott.

However - if the guy is trying to recover from 2 Pentium Pro chips and he has literally covered them with HCl and added Nitric that's far too small a solution to dissolve the metals involved, as I'm sure you'd agree. We all do have a tendency to offer advice based upon a small portion of the relevant information, and then often end up having to amend said advice when the true facts emerge.

I was just thinking that in many cases we'd be able to help better and cut down on the "ifs buts and maybes" by just getting the proper facts to start with. It would save a lot of time and confusion in many of the cases we deal with.

Does that sound reasonable or just daft?

Regards

Jon
 
spaceships said:
Hi Can we get some perspective on this please as it would help with the answers?

How many Pentium Pro processors are you recovering from and what is the total volume of liquid in the original AR solution?

15 Pentium Pros in a 2L beaker with 500ml HCL and 500ml water. Nitric added 3ml at a time.

Here is what it looks like now: https://www.dropbox.com/s/8nznh75wnvx6gb3/2015-10-20 20.38.25.jpg?dl=0

There is still quite a bit of gold left on the chips. I think I'll crush the rest and run them through a fresh solution.

https://www.dropbox.com/s/l0v6iwizrkz3qpz/2015-10-20 20.23.26.jpg?dl=0
https://www.dropbox.com/s/fdk894ob6depzvn/2015-10-20 21.02.34.jpg?dl=0
 
Thanks that puts some better perspective on it I appreciate that. Would anyone care to amend their advice?
 
geedigity said:
I would think that when you were dissolving the foils and black powders, you were refining. When you are dissolving the gold and base metals as in your current situation, you are reclaiming. Therefore, you would have more base metals in solution since you chose to dissolve everything.

so after everything is dissolved, you will first have to get rid of the extra nitric, then drop the gold (probably more contaminants in this batch than in prior ones), then refine the dropped gold.

Reclaiming vs refining - that was an epiphany moment for me. Thanks!!

kadriver said:
I've had some experience with this.

This is why it is so important to understand the reactivity series of metals chart.

kadriver

I see your point. Thank you very much for a very educational post!

NobleMetalWorks said:
When I made the suggestion to expand your solution, what I am meaning is to provide more room for metals to be dissolved into solution. You can expand a solution by adding more acids, or water or? All dependent upon what type of solution you have, and what your intent is. You expanded your solution when you added more acid, but as the acid was attacking the base metals instead of the gold, it seemed that your AR solution was not working, or working on slowly.

Scott

Thank you for that explanation!

spaceships said:
Thanks that puts some better perspective on it I appreciate that. Would anyone care to amend their advice?

I should have included this information from the start. Will make sure I do so in the future.

Thank you everyone for your help. You are all awesome!
 
I've got some pentium pro CPUs on the way - about 10. When they get here I'll make a detailed video showing how to recover the gold, then how to refine it to high purity.

The ferrous metals MUST be removed first with straight hydrochloric acid boils. The foils can then be easily dissolved with AR with the ceramic still in the beaker. Hydrochloric acid by itself should not dissolve the gold, but hot hydrochloric acid will dissolve the ferrous metals.

I believe that it is the presence of any ferrous metals that is causing the problem here. Hot hydrochloric acid should be the remedy.

This will be my first attemp at recovering and refining gold from Pentium Pro CPUs. Should be interesting!

kadriver
 
kadriver said:
I've got some pentium pro CPUs on the way - about 10. When they get here I'll make a detailed video showing how to recover the gold, then how to refine it to high purity.

The ferrous metals MUST be removed first with straight hydrochloric acid boils. The foils can then be easily dissolved with AR with the ceramic still in the beaker. Hydrochloric acid by itself should not dissolve the gold, but hot hydrochloric acid will dissolve the ferrous metals.

I believe that it is the presence of any ferrous metals that is causing the problem here. Hot hydrochloric acid should be the remedy.

This will be my first attemp at recovering and refining gold from Pentium Pro CPUs. Should be interesting!

kadriver

I feel you should do some more research and refine your process.
 
You have too many steps in your process Kadriver.

Smash the thin black ceramic caps off the base of the chips and remove the waste. Then simply break up the whole processor with a hammer (the gold plated lids do actually break) and process the whole lot at once in AR.

I can't agree with your suggestion of ferrous metals causing a problem I am afraid because I have processed many of these and never had that issue.

Regards

Jon
 
kadriver said:
I've got some pentium pro CPUs on the way - about 10. When they get here I'll make a detailed video showing how to recover the gold, then how to refine it to high purity.

The ferrous metals MUST be removed first with straight hydrochloric acid boils. The foils can then be easily dissolved with AR with the ceramic still in the beaker. Hydrochloric acid by itself should not dissolve the gold, but hot hydrochloric acid will dissolve the ferrous metals.

kadriver

I did the hot HCL rinse with the leftovers. The bath ended up a deep purple, almost black. I guess it dissolved lots of impurities.

They've been in hot AR for the past 3 days. Had to add HCL a couple of times and add about 10ml nitric a couple of times a day. This morning the reaction was still going.

Not sure if the hot HCL will improve the yield or not, but it certainly improved the color of the AR solution. It's amber instead of green.
 
Processed the solution, got a few grams - less than 5 - of dirty gold powder and started again with the processors.

This time, I crushed them to an average of about 6 fragments each and lots of dust. Boiled them in HCL until that got too dark to see if the color was changing. Added that to the stock bucket and repeated the HCL boil. After the color stopped changing, put that in the stock too. Added clean HCL, heated it and started adding nitric. Added about 50ml over 2 days. Added more HCL, added more water, keep adding nitric and the reaction is still going after 4 days. There is also a yellowish film forming on the beaker.

AR 4 days.PNG
Should the reaction be going this long or is it having a Ground Hog's Day complex? Like something pushing the gold out of the solution and it getting re-dissolved over and over? And what is that film on the glass?
 
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