Gold Pin Refining - Solid Gold? Unexpexted Results. Help?

[Crank]

All,
I should first say thank you to the members here. There really is some great info here for new hobbyist like myself.
I recently started processing some scrap connectors that have gold pins. To date, I've processed a few different materials all in the hopes of having a lot of foils ready to go. That way I can do batches of aqua regia all at the same time.
I've stripped some gold plated shields as well a handful of PCBs. They both had one thing in common- when placed in AP, there is a near immediate reaction.
Yesterday, I did a test by putting 20 or so pins in an AP solution. It was odd because nothing happened. I told myself to be patient and check it again 24 hrs later to see if there was a change. I checked the pins again this morning- again, no reaction at all. I've left those pins still in AP and will give them a week and will check once again.
Given what I found, I figured I would try melting some pins in a spare small crucible I bought and haven't used used. I took about 20 or so pins (shame on me for not documenting a measuring!) and I stated to apply some heat with a MAP torch. It took a bit, but the pins started to combine. Eventually, I had a red hot BB moving around in the crucible.
I dropped it into some water and found it came out more of a copper color than gold, so I put it back in the crucible and heated it again until it was a BB. I added a little flux and it seems like it separated impurities. I did this whole process 2 more times to try and see if I could get a more pure gold colored BB. It weighs .3g
I drenched it again and washed it with water. I decided to drop the nugget into some AP to see if anything happened. Again, nothing.
Now I'm baffled. I've attached a picture of what the pins look like next to the melted metal. It still looks a little dirty, but is it possible this is a nugget of gold?
I've not bought sulfuric yet because of what I noted below about wanting to have a lot of processed foils ready. I know that I could see if this is gold by trying to dissolve it into a solution. I also don't have what I need to do a stannous test.
I'd appreciate opinions

 

[efka]

I guess the PCBs had solder on them? The tin in the solder reacts strongly with AP/HCl, copper on the other hand reacts slowly. Another possibility is that your AP went bad from the PCB stripping. Only CuCl2 is reusable over and over, if you have a mix of metals in your AP solution, it can stop working

 

[Yggdrasil]

All,
I should first say thank you to the members here. There really is some great info here for new hobbyist like myself.
I recently started processing some scrap connectors that have gold pins. To date, I've processed a few different materials all in the hopes of having a lot of foils ready to go. That way I can do batches of aqua regia all at the same time.
I've stripped some gold plated shields as well a handful of PCBs. They both had one thing in common- when placed in AP, there is a near immediate reaction.
Yesterday, I did a test by putting 20 or so pins in an AP solution. It was odd because nothing happened. I told myself to be patient and check it again 24 hrs later to see if there was a change. I checked the pins again this morning- again, no reaction at all. I've left those pins still in AP and will give them a week and will check once again.
Given what I found, I figured I would try melting some pins in a spare small crucible I bought and haven't used used. I took about 20 or so pins (shame on me for not documenting a measuring!) and I stated to apply some heat with a MAP torch. It took a bit, but the pins started to combine. Eventually, I had a red hot BB moving around in the crucible.
I dropped it into some water and found it came out more of a copper color than gold, so I put it back in the crucible and heated it again until it was a BB. I added a little flux and it seems like it separated impurities. I did this whole process 2 more times to try and see if I could get a more pure gold colored BB. It weighs .3g
I drenched it again and washed it with water. I decided to drop the nugget into some AP to see if anything happened. Again, nothing.
Now I'm baffled. I've attached a picture of what the pins look like next to the melted metal. It still looks a little dirty, but is it possible this is a nugget of gold?
I've not bought sulfuric yet because of what I noted below about wanting to have a lot of processed foils ready. I know that I could see if this is gold by trying to dissolve it into a solution. I also don't have what I need to do a stannous test.
I'd appreciate opinions

The bead looks like copper.
Are you bubbling air through your AP?
Have you refreshed it with some HCl?

 

[Crank]

The bead looks like copper.
Are you bubbling air through your AP?
Have you refreshed it with some HCl?

The AP hasn't been refreshed with HCL. I did add some hydrogen peroxide before i left it overnight, however.
I'll try a bubbler and give the pins a week to see if there is any noticeable reaction

 

[Crank]

Here is another picture. It looks more gold colored here.

 

[butcher]

I like to make nitric acid with thick gold-plated pins in a recovery process of gold...

You may need to cut thick gold plated pins into small pieces in order to better expose the copper core to the cupric chloride leach, the thick gold plating can make it hard for the leach to reach the copper.

 

[Alondro]

I like to make nitric acid with thick gold-plated pins in a recovery process of gold...

You may need to cut thick gold plated pins into small pieces in order to better expose the copper core to the cupric chloride leach, the thick gold plating can make it hard for the leach to reach the copper.

Need to be sure the pins are copper core and not brass. Brass ones will have tin, and lead to metastannic acid.

I use the CuCL2-HCl method. Just need to swirl it now and then, and in about a week, most of the base metals are dissolved, and the only solids are gold foils and Cu(I)Cl crystals, which can be easily dissolved with fresh HCl.

 

[Alondro]

Here is another picture. It looks more gold colored here.

You probably have a copper-gold alloy now which HCl-peroxide won't attack easily. Probably time for AR or HCl-bleach to dissolve the whole lump.

 

[FrugalRefiner]

Need to be sure the pins are copper core and not brass. Brass ones will have tin, and lead to metastannic acid.

Brass is an alloy of primarily copper and zinc. Bronze is an alloy of primarily copper and tin.

Dave

 

[BlackLabel]

I also think, the pins were high quality/thick plated (medical, military or very old).
The AP was unable to penetrate the plating.
Cutting the pins in three pieces would have opened the brass core for the AP.
Now you might have a gold-copper alloy of about 12k and the AP can't attack it.

You could try some kind of "poor mans inquartation":
Remelt your button with the same amount of copper, pour it into water in order to get pieces with larger surface and try it again with AP.
I guess, you will end up with something between 0.15 and 0.2 grams of gold.

Because of the small amount, you have to be very careful on decanting and filtering.
Keep all waste solutions in a stock pot.

Good luck!

 

[Crank]

I also think, the pins were high quality/thick plated (medical, military or very old).
The AP was unable to penetrate the plating.
Cutting the pins in three pieces would have opened the brass core for the AP.
Now you might have a gold-copper alloy of about 12k and the AP can't attack it.

You could try some kind of "poor mans inquartation":
Remelt your button with the same amount of copper, pour it into water in order to get pieces with larger surface and try it again with AP.
I guess, you will end up with something between 0.15 and 0.2 grams of gold.

Because of the small amount, you have to be very careful on decanting and filtering.
Keep all waste solutions in a stock pot.

Good luck!

I think I may just chalk up that button to a learning experience. I don't want to waste the time on trying to make something out of it when I still have other raw material to refine.
You are correct - the pins are all stripped down from scrapped mil components.
This evening I am trying to remove all of the pins from the epoxy thats holding them. I would like to dissolve them in AR instead of AP but I want to keep the epoxy away from that solution. I ordered some sulfuric today.
In the meantime, I am also still running the test noted above in one of my earlier posts. I have a small batch of pins still in epoxy that have been processing for 24 hours in fresh AP with a bubbler. I'm still seeing no noticeable reaction where gold is separating. I may throw in a couple pins that I've snipped into pieces.

 

[FrugalRefiner]

I think I may just chalk up that button to a learning experience. I don't want to waste the time on trying to make something out of it when I still have other raw material to refine.

Throw it in your stockpot. As you put your waste acids in, they will consume the base metals, and in the end, you'll recover the gold without any additional effort or expense.

Dave

 

[Crank]

I wanted to follow up on this to report my findings. I've left the pins in AP for about a week now with no observable change. I do see that some of the pins now feel a little 'soft', but I am not seeing a discoloration of the AP which would indicate that there is a high level of copper present.
Rather than just hitting some pins with a torch, I'm considering putting some pins right onto AR. Would anyone advise against this?
On page 41 and 42 of Hoke, she speaks to a treatment using only Sulfuric. Should I do this first?

 

[orvi]

I wanted to follow up on this to report my findings. I've left the pins in AP for about a week now with no observable change. I do see that some of the pins now feel a little 'soft', but I am not seeing a discoloration of the AP which would indicate that there is a high level of copper present.
Rather than just hitting some pins with a torch, I'm considering putting some pins right onto AR. Would anyone advise against this?
On page 41 and 42 of Hoke, she speaks to a treatment using only Sulfuric. Should I do this first?

I never had the luxury of using nitric to eat BM from pins and either time to run AP bucket. So to this day, I only use AR for digestion of any metal based gold materials (that is suitable). You need to get familiar with very dark coloured solutions, which are hard to see through. I regularly do pins in AR... no problem. It isn´t the nicest method, gold drop is many times very light and require whole day to settle properly, and of course need second refine. But recovery rate is practically the same as with other methods.
Take a test batch and dissolve it in AR, few pcs. Ammount of gold you can also judge from the colour of the solution.
And don´t be fooled by golden colour of the alloy - either brass or bronze can be that coloured. And also hard silver alloys (AgCusomething).

 

[orvi]

All,
I should first say thank you to the members here. There really is some great info here for new hobbyist like myself.
I recently started processing some scrap connectors that have gold pins. To date, I've processed a few different materials all in the hopes of having a lot of foils ready to go. That way I can do batches of aqua regia all at the same time.
I've stripped some gold plated shields as well a handful of PCBs. They both had one thing in common- when placed in AP, there is a near immediate reaction.
Yesterday, I did a test by putting 20 or so pins in an AP solution. It was odd because nothing happened. I told myself to be patient and check it again 24 hrs later to see if there was a change. I checked the pins again this morning- again, no reaction at all. I've left those pins still in AP and will give them a week and will check once again.
Given what I found, I figured I would try melting some pins in a spare small crucible I bought and haven't used used. I took about 20 or so pins (shame on me for not documenting a measuring!) and I stated to apply some heat with a MAP torch. It took a bit, but the pins started to combine. Eventually, I had a red hot BB moving around in the crucible.
I dropped it into some water and found it came out more of a copper color than gold, so I put it back in the crucible and heated it again until it was a BB. I added a little flux and it seems like it separated impurities. I did this whole process 2 more times to try and see if I could get a more pure gold colored BB. It weighs .3g
I drenched it again and washed it with water. I decided to drop the nugget into some AP to see if anything happened. Again, nothing.
Now I'm baffled. I've attached a picture of what the pins look like next to the melted metal. It still looks a little dirty, but is it possible this is a nugget of gold?
I've not bought sulfuric yet because of what I noted below about wanting to have a lot of processed foils ready. I know that I could see if this is gold by trying to dissolve it into a solution. I also don't have what I need to do a stannous test.
I'd appreciate opinions

Stannous test can get you rough idea of how much gold is in the sample judging by the colour. I would advise to dissolve that melted blob in AR and test with stannous. If they run over 1% Au (10g/kg), it would be clearly visible and stannous will be plain black colour. Very deep. With signs of individual particles separating from the colloid.
If it is serious % AuCu alloy, you will clearly see the colour of the AR solution - much more yellowish/orange-y tinge. Stannous would be plain black, opaque. Altough, I never encountered AuCu alloy in electronics (also MIL, old Soviet, any), but I stumbled across Au75Ag, Au95Ni and Au70Ag25Ni5 several times.
Very easy to spot the difference with plating as gold has notorious gold colour ( ) but these alloys are pale in colour, many times with greenish tinge, and some does not resemble gold at all (Au70Ag25Ni5). Very rare to find them, almost exclusively found as material of contact points in high-end relays, switches, sliders in potentiometers and rotary switches.

 

[Findm-Keepm]

Another possibility: Au-plated Beryllium Copper pins. They are even more common these days, especially in wire-to-board applications where flex may be an issue. Also, most spring "fingers" in card-edge connectors are likely plated BeCu.

I had to go the H2SO4 cell to strip the gold from a bunch of (known) Gold-plated BeCu pins.

 

[Alondro]

Another possibility: Au-plated Beryllium Copper pins. They are even more common these days, especially in wire-to-board applications where flex may be an issue. Also, most spring "fingers" in card-edge connectors are likely plated BeCu.

I had to go the H2SO4 cell to strip the gold from a bunch of (known) Gold-plated BeCu pins.

Gotta be REAL careful with beryllium salts. They're extremely toxic, similar in toxicity to arsenic! 4mg is enough to be considered an immediate health danger!

 

[orvi]

Another possibility: Au-plated Beryllium Copper pins. They are even more common these days, especially in wire-to-board applications where flex may be an issue. Also, most spring "fingers" in card-edge connectors are likely plated BeCu.

I had to go the H2SO4 cell to strip the gold from a bunch of (known) Gold-plated BeCu pins.

With typical pins, there are practically four major possibilities of what they can be made of:
Brass (CuZn)
Bronze (CuSn)
Magnetic alloys (kovar etc.)
Beryllium copper (CuBe)
Other alloys are rare, saying from my personal experience. Counting hard silver (AgCu) or other strange copper alloys.

Convenient is to zapp them with XRF, altough I know that majority of people does not have access to one. If it is brass or bronze, you will clearly see by presence of either zinc or tin. Kovar is easily distinguished as it is slightly magnetic or magnetic. And if the XRF is showing only copper - no Sn or Zn - you can be quite sure it is beryllium copper, since XRF does not see beryllium.
And yeah, you need to cut off the tinned parts with solder - they will mess up whole "assay". XRF will conveniently see through gold plating and show also the material of the pin, but ratios may be skewed due to gold "shielding". You will regularly see nickel, as it is used as underplating on copper based materials.

By experience with certain type of machine, you can guesstimate the gold content of the pins by % of gold shown - in my case with Olympus Vanta, I empirically learned that to 10g/kg Au it goes with order of 3. 3% Au = 1g/kg. VERY VERY ROUGHLY. You also need to account for the material thickness. I just use it as convenient and very quick tool to distinguish good and poor pins, nothing else. Melting "assay" gives you +-5% result when button is properly melted, sanded and zapped with XRF.

Don´t forget to account for melting loss - thus weighing raw pins and also melted flattened button. You need just something like 1,5g of pins to perform this conveniently. Melting in quartz dish with oxy/propane is done under 3-4 minutes, additional ca 3 mins for cleaning, flattening, weighing and sanding. 2 minutes for zapping with XRF and doing the math. If you are well setup, you can do this pseudo-assay in less than 10 minutes whole.
When I hadn´t regular access, I done like 5-10 these pseudo-assays in advance, then paid few bucks for the machine time in one shop and during 10 minutes zapped all buttons and had results in my hand

 

[orvi]

Gotta be REAL careful with beryllium salts. They're extremely toxic, similar in toxicity to arsenic! 4mg is enough to be considered an immediate health danger!

I would say worse, because arsenic is somewhat excreted from body, altough it is very cumulative. Be is very small and has insane charge to radius ratio. It binds everywhere where magnesium does, and bond is permanent. At least this is what I said in textbooks. Due to very small ionic radius, it penetrate skin and membranes like nothing

 

[Daniel0007a]

A video on strips if they are gold plated may contain 1-2 percent gold. This is from strips. Interesting but you will prob not get a lot of gold. Streeps took 4760 g of gold pins and got 23 g gold out of it.