# Have I struck gold?



## bemate (Sep 28, 2016)

I came across an old switchboard of some kind that I was able to get pieces off, judging from the overall appearance, it's late 60's, early 70's. There were some old-style circuit boards and a generous amount of gold-coated pins.

The boards have a nice, thich layer of metals on the plated fingers, you can really feel the ridged structure indicating they have a fairly thick coating, consistent with the age. However, I'm more unsure about the covered conductors on the rest of the cards, they are more reddish, but scraping them shows a golden colour underneath a thin top layer (see photos). My question is: does the gold coating from the pins comtimue all across the boards or is that likely copper? If so, how to best test it, just drip HNO3 on and look for a reaction?


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## jason_recliner (Sep 28, 2016)

bemate,
The rest of the board is copper, as you suspected. If you wish you could confirm it with a drop of nitric, as you suspected.

Your hypotheses are running pretty well so far.


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## goldsilverpro (Sep 28, 2016)

Figure about $0.40 for every square inch covered by gold on the fingers.


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## FrugalRefiner (Sep 28, 2016)

bemate said:


> The boards have a nice, thich layer of metals on the plated fingers, you can really feel the ridged structure indicating they have a fairly thick coating, consistent with the age.


Most of the thickness you feel is the copper under the gold. Circuit boards start with a solid layer of copper over the whole board. The copper is etched away where it's not wanted, leaving the copper traces you see. The contact areas (fingers) are then plated with about 30 microinches of gold.

Dave


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## bemate (Sep 28, 2016)

Thanks for replying, pretty much as I expected then, better than modern-day RAM-fingers, but not too much value.

Anyway, I have a follow-up question: I saw that some of the cards had some transistors, pried one off and opened it. I pulled out one of the pins going into the transistor and looked at it through a stereo lens. While it looks as though it is fused from an outer part of base metal, or possibly silver, to a more or less solid gold part running through the transistor, I can't quite make myself believe that. Could anyone comment if they have seen anything like this before?


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## goldsilverpro (Sep 28, 2016)

The gold plating on fingers was no thicker in 1972 than it is today. I started in this business in 1966 and the thickness on wear surfaces (connector pins, fingers, etc.) was the same as today - 30 millionths of an inch.

The inside fingers on those DIP legs (last 3 photos) are plated as well, probably about the same thickness. No solid gold on any of this stuff. About the only solid gold on electronics scrap are the bonding wires. With those, there are either 2 miles or 4 miles of wire per troy oz of gold, depending on whether the diameter of the wire used was .001" or .0007",


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## anachronism (Sep 28, 2016)

goldsilverpro said:


> The gold plating on fingers was no thicker in 1972 than it is today. I started in this business in 1966 and the thickness on wear surfaces (connector pins, fingers, etc.) was the same as today - 30 millionths of an inch.



Chris - do you think from your experience that this is cast in stone regardless of manufacturer, country and application?


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## g_axelsson (Sep 28, 2016)

There have been some really thin plating on some cards, some is hardly gold toned. I used some PCI-cards like that to create thin golden films in water and captured it on a small copper grid. The films were then examined in a transmission electron microscope and you could see the individual crystal areas of the gold film. At least that one was transparent to electrons and that indicated 100-150 nm thickness. Any thicker and it becomes opaque.

So maybe any plating worth using as a contact surface is the same today as for 30 years ago, but some manufacturers have cut corners and ended up with inferior plating that actually can fail in a short time.

I know that as a fact, as the last card I designed used gold flash (ENIG) instead of fully plated fingers. On the other hand I'm using the cards for a private project so I'm not intending to sell it to a customer. :mrgreen: 

Göran


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## goldsilverpro (Sep 28, 2016)

anachronism said:


> goldsilverpro said:
> 
> 
> > The gold plating on fingers was no thicker in 1972 than it is today. I started in this business in 1966 and the thickness on wear surfaces (connector pins, fingers, etc.) was the same as today - 30 millionths of an inch.
> ...


Nothing is cast in stone when it comes to plating and all 3 of those variables can exhibit large thickness differences. When I speak about thickness, I'm talking averages. It's only a guide and an educated guess. We must start someplace. There is no simple way of determining thickness. 

We know that Russian electronics are often plated thicker than the Western counterparts. The US manufacturers probably have variations in their thicknesses. Parts used in a rocket are probably plated thicker than those same parts used in a TV.

Were I to set up a refinery, the 1st investment I would make would be in a fire assay setup. If everyone had fire assay, discussions such as this wouldn't exist. As a refiner, I don't ever remember plating thicknesses ever being discussed. The question was always, "What was the assay?"


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## bemate (Sep 29, 2016)

An update for those interested:

I also removed the connector board the cards were slotted into:


While not looking forward to the task of removing them all only to find they were not gold plated, the colour looked slightly too much coppery, I decided to do a small test.

I snipped off a piece of one pin and made a small setup in a fume hood:




I added 1 ml MQ-water (18,2 MOhm) and 1 ml 65% HNO3. The reaction was immediate and a clear blue colour emerged:


(Edit: The test tube on the right is the transistor legs from my previous post in the same solution, note the lack of blue colour...)
After about an hour I was left with a bright blue solution and tiny gold flakes, disproving my fear that the pins were solid copper rather than plated:



Happy that my pins contain gold, I started quantifying the board, and after prying out a single pin, i weighed it and found a single pin to be 353mg, with 30 pins per connector, some of them double rows, I calculated there are a bit more than 600 grams of cleaned pins. But, as can be seen in the first picture, there are wires all over the place, luckily only a few are soldered, the rest are wound around the pins, but still a mammoth task to clean them.

So, the question is then: any useful ideas on how to free the pins before further processing? Burning the plastics away is probably the easiest solution, that would likely take care of a good portion of the solder as well, but are there any other creative ideas? I thought maybe sticking a piece in the freezer to try and make the plastic brittle would help a bit, then I could just hammer away and sort through the debris for the pins...

Edited to add picture comment about test tube No.2.


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## bemate (Sep 29, 2016)

There was not room for all the pictures in my last post, just some details on the connectors and pins:


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## Barren Realms 007 (Sep 29, 2016)

Try putting them in the freezer overnight then take out one or two and see if they become brittle enough to break apart when hitting them with a hammer.


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## Topher_osAUrus (Sep 29, 2016)

Those kindof look like ones i had, where i could fit a screwdriver under the bottom part and pry it so it split open.

Some were troublesome and didnt split well... So i left them outside on a cold winter night, then the next morning beat them to death with a hammer, as Barren suggested. Worked well (to remove the pins AND relieve stress 8) )

Edit to fix where to were..grammar matters!


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## bemate (Sep 29, 2016)

I'll give the freezer a go then, might be even better in the -80 freezer. Hopefully that will work. I've only cleared a quarter of the pins so far, but I'll post an update next week when I can try it out.

Thanks a lot for the input guys, I really appreciate you taking the time to help a newbie out.


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## g_axelsson (Sep 29, 2016)

bemate said:


> I'll give the freezer a go then, might be even better in the -80 freezer. Hopefully that will work. I've only cleared a quarter of the pins so far, but I'll post an update next week when I can try it out.
> 
> Thanks a lot for the input guys, I really appreciate you taking the time to help a newbie out.


Nope, the -80 freezer is a bad idea, you would freeze the nitric acid too.
http://nitrogen.atomistry.com/physical_properties_nitric_acid.html
The idea is to lower the solubility of the sulfate and then to pour off a nitric acid low in dissolved sulfate salt.

Göran


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## bemate (Sep 29, 2016)

You misunderstood my intent Gøran, I'm talking about freezing the unprocessed connectors to make the plastic brittle. Then I can (hopefully) smash them with a hammer to break apart the connectors and free the pins. No chemicals at this stage, the setup I tried was just the snipped ends off of two pins to look for gold foils. :wink:


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## g_axelsson (Sep 29, 2016)

My bad, must have read a post about making nitric acid by the cold method from nitrates and sulfuric acid and then read your post and mixing the threads together.  

For smashing plastic it will probably work like a charm... and I think protective goggles and well isolated gloves is a must, but coming from Norway I know the cold won't be a problem for you.  

Göran


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## bemate (Sep 29, 2016)

g_axelsson said:


> My bad, must have read a post about making nitric acid by the cold method from nitrates and sulfuric acid and then read your post and mixing the threads together.
> 
> For smashing plastic it will probably work like a charm... and I think protective goggles and well isolated gloves is a must, but coming from Norway I know the cold won't be a problem for you.
> 
> Göran



Haha, no that won't be a problem. I'll grab my skiing goggles and wool mittens... :lol: 

Or i could just wait a few months and leave them outside, that should work just as well.


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## bemate (Sep 30, 2016)

I did a rough estimate on the surface area of the pins, measuring them to 45mm in length, about 1,7mm wide and between 0,5 and 1mm in thickness. Rounding down to err on the side of caution, I estimate each pin to have a surface area of about 200mm2.

With 58 rows of 30 pins, that gives me a total surface area of about 3500 cm2. Calculating for 30 microinches, or 0,76 micrometers, that gives a total volume of about 0,27cm3, with gold at 19,3gm per cm3 should give about 5 grams of gold.

Does that sound reasonable for 600 grams of pure pins, not counting in the weight of wires, solder etc?

Also, I tried putting a couple of connectors in the -80 freezer for a couple of hours. It did make the plastic brittle, but the connectors are very thick plastic, so smashing them with a hammer did not help too much. I'll keep looking at possible ways, just trying small scale until I settle upon a method I like.


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## jason_recliner (Sep 30, 2016)

5g in 600g = 120:1 = 0.8%, and sounds conceivable for plated pins.
I expect that one's processing method would affect the final yield as much as would the originating material. If you would be so kind, share with us your own final result.


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## bemate (Sep 30, 2016)

jason_recliner said:


> 5g in 600g = 120:1 = 0.8%, and sounds conceivable for plated pins.
> I expect that one's processing method would affect the final yield as much as would the originating material. If you would be so kind, share with us your own final result.



Will do, but I'm just starting out at the middle of the learning curve, so I estimate it will be a good while before I do any actual wet work. The tests I have performed so far are just qualitative tests to get a feel for the material. Unfortunately I have neither time nor facilities to process any kind of amounts, yet...

I will, however, keep that particular batch of pins separate from my other materials as I slowly build my stockpile. And let's not forget I still have no idea how to separate the pins from the plastic in a reasonable way, I'd rather not have to burn that much plastic...


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## Barren Realms 007 (Sep 30, 2016)

Well to make a long post short if they were mine I would just remove the wires from the pins and process them still in the connectors in poor mans AR and drop out the gold. But that is just me. You are not at the point in your processing experience that you should feel comfortable doing them this way and I'm not advising you to do them this way.

I did mention to leave the connectors in the freezer overnight. Leaving them in the freezer for just a couple of hours is not a long enough time for them to become cold enough to shatter when hit with the hammer.

Your success in this field of endevour with depend on how well you follow instructions given to you.


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## Topher_osAUrus (Sep 30, 2016)

To add to Barren's post.

Patience is what makes or breaks you (and the cases in this, er, case..)

I do believe that i got impatient and threw a couple into AR, which went horribly, as the plastic turned to mush and covered everything. They went fine in AP, it was just tedious to spray out every flake of gold from inside the connectors.

But, those are green, mine were black. Color might not be the only different (composition of the plastic, may be as well)

But, you should let them freeze for a day or two, maybe even throw them in the freezer wet, so the water expands inside the plastic. Then beat them like nobody's business.... Or find a good old blender that can do the beating for you.


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## bemate (Sep 30, 2016)

Topher_osAUrus said:


> But, you should let them freeze for a day or two, maybe even throw them in the freezer wet, so the water expands inside the plastic. Then beat them like nobody's business.... Or find a good old blender that can do the beating for you.



Now that might just do the trick, the water should permeate the connectors and help with the breaking. That's exactly the kind of thinking I like.  

As for rushing the freezing: (and not to be defensive) It was a lab freezer at -80 degrees celcius, not a standard -20, and it was only 2 connectors so they were completely frozen through. Maybe not all the way to -80, but well below -20. Though I will concede that time also plays a role.

I have also looked at what makes plastic brittle under normal circumstances, and apart from age, it seems heat and UV radiation might be alternatives.

I'll try baking one at a low heat for a while and put one under a UV-lamp in addition to freezing with water. If it works out, I'll probably make a separate post in the techniques-forum about it.

Again, thanks for the input guys, I really appreciate it.

B


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## anachronism (Sep 30, 2016)

I've had those green things before. Now assuming they are the same, and we can't be sure of that but a week in HCl dissolved the plastic on mine.


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## bemate (Oct 5, 2016)

As it turns out, the answer was simple: Acetone. I left a sample over night in Acetone, and lo and behold: the plastic crumbled like cheese curds. I am now in the process of extracting the pins, and for most of the connectors it's more or less a question of pulling them apart by hand.










So, that cleared up that well enough, next step now is to burn off the rest of the plastic from the small wires and try to get rid of the solder at the same time. I was thinking I'd roast them with a simple propane torch designed to burn weeds. If I do this on a stainless steel mesh the solde should mostly just drop off provided I get it hot enough.


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## upcyclist (Oct 5, 2016)

As an aside, don't forget to first run your pins through HCl to dissolve any tin in the solder. You'll read lots here about the metastannic acid mess you'll create if you go straight to nitric or AR 

Speaking of things you'll read about here, also roast your solids after the HCl soak to remove any chlorides, lest a follow-on nitric soak becomes AR before you're ready for it. Always roast between acids until you're ready for AR.


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## bemate (Oct 6, 2016)

upcyclist said:


> As an aside, don't forget to first run your pins through HCl to dissolve any tin in the solder. You'll read lots here about the metastannic acid mess you'll create if you go straight to nitric or AR
> 
> Speaking of things you'll read about here, also roast your solids after the HCl soak to remove any chlorides, lest a follow-on nitric soak becomes AR before you're ready for it. Always roast between acids until you're ready for AR.



Good points, will keep it in mind.
Actually, since the pins appear to be pure copper without any nickel as far as I can see, I was thinking about doing a slow AP leach which would give me a fairly pure copper chloride solution to use on future AP leaches. I want to make sure I remove as much other metal as possible beforehand.
My internal struggle now is whether to invest some time to sort my pins to educate myself with them, or keep them collected to calculate yield on the batch as a whole...

Mind you, for now I'm just reading, thinking and doing micro-scale reactions in test tubes at the lab where I work to familiarize myself with the sources and chemicals.

I'm looking at the possibility of making a closed AP-setup with fumes directed through a scrubber. That way I can set it up outside my garage without being an eyesore.
But it's still a theoretical project so far.


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## upcyclist (Oct 6, 2016)

bemate said:


> upcyclist said:
> 
> 
> > As an aside, don't forget to first run your pins through HCl to dissolve any tin in the solder. You'll read lots here about the metastannic acid mess you'll create if you go straight to nitric or AR
> ...


AP, since it's an acidic chloride solution, will do the trick too. Realize that afterwards, then, your solution won't actually be "fairly pure copper chloride"--it'll be a mix of copper & tin chlorides (as well as nickel, lead, etc.--whatever it ate), so it might lose power after a while until you refresh it with HCl. 

Lots of ways to skin a cat, you find the one that works best for you.


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## jason_recliner (Oct 8, 2016)

bemate said:


> My internal struggle now is whether to invest some time to sort my pins to educate myself with them, or keep them collected to calculate yield on the batch as a whole...


On the subject of investing time, one of the most significant characteristics of plated pins is their notoriously low yield. The precious metal value is so low that they are rarely worth any great deal of human time. For this reason it is not uncommon practice to toss them in a bucket and forget about them for a few months. This way one wastes the least oxidiser, electricity and human interaction.

If I were to do pins or equivalent these days, I would also dilute the HCl concentration from ~30% to just under 20%; this is HCl's azeotrope. My remedial-level chemistry comprehension is that any higher concentration than this will only evaporate off to that value anyway, but I welcome any correction on this point.


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## upcyclist (Oct 8, 2016)

Doh. I thought the azeotrope of HCl was about 35%. Now I know better, and wait to see what people say about your idea.

Sent from my SAMSUNG-SM-G891A using Tapatalk


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## bemate (Oct 13, 2016)

I will go out on a limb and assume that some of you find this thread somewhat interesting.

Having soaked the plastic parts and extracted the pins over a few days, I took the time to sort them as well. Some would probably argue that is wasted time, but then again, you don't calculate the price per kg for fish you catch when you go fishing for recreation (I hope...)

I sorted the pins into three piles; clean ones, soldered ones and the vast majority that is with wires wound around, though not soldered.



I also weighed several of the clean ones and found the average weight to be 324mg, making it 633g total weight without solder and wires.

And so comes a small question: if I take the soldered ones and soak in HCL, the solder should dissolve nicely. That would give me a tin/lead-solution, possibly with some other contaminations. If I then treat this solution with a bit of sulphuric acid, the lead should drop out as sulphate. Would the remaining (mostly)tin solution then be usable as a stannous chloride test solution?


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## upcyclist (Oct 13, 2016)

I would use known, clean ingredients for a test solution like that. I would not go with 'I think it's mostly tin chloride'. Get yourself some lead free sinkers or something like that, and use those.

Sent from my SAMSUNG-SM-G891A using Tapatalk


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## bemate (Oct 13, 2016)

upcyclist said:


> I would use known, clean ingredients for a test solution like that. I would not go with 'I think it's mostly tin chloride'. Get yourself some lead free sinkers or something like that, and use those.
> 
> Sent from my SAMSUNG-SM-G891A using Tapatalk



I had an inkling that would be the first answer... :wink: I'll look for some of those singers, or I might just buy some tin bars online. For some reason, pure tin is very hard to find in less than several kilogram batches here... It's almost as if no one casts their own tin soldiers anymore. But that's a minor inconvenience, I don't plan on having any solutions I need to test for quite some time anyway.


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## g_axelsson (Oct 13, 2016)

Check in a second hand store for banged up pewter objects and buy a cheap one, it will last a lifetime.

Göran


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## anachronism (Oct 13, 2016)

One reel of tin solder will also last a lifetime. It's the blue stuff in the UK. Readily available online or in your local DIY store.


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## bemate (Oct 14, 2016)

anachronism said:


> One reel of tin solder will also last a lifetime. It's the blue stuff in the UK. Readily available online or in your local DIY store.



The closest I've found so far is 99,3% Tin and 0,7% Copper. Will that do? I assume I want the clean type without solder incorporated in the thread?


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## jason_recliner (Oct 14, 2016)

Yes, that's spot on and is what I use.
A little (or even much) copper or lead (i.e., Göran's pewter) will not throw off your tests at all.


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## anachronism (Oct 14, 2016)

As Jason said- it's perfect. 

It's also cheap, effective and you'll never have problems. Keep a small jar (literally a few ml) of weak gold chloride to one side when you've made some. You can regularly put a drop of it with a drop of your stannous to provide a base line test to make sure your stannous is working.


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## upcyclist (Oct 14, 2016)

Exactly--I hope you didn't think I meant your source material had to be 100% tin, just mostly tin and a known saturated solution. You'll see when you search on how to make your own solution, but basically you use full-strength muriatic and keep an excess of tin in the solution (that not only keeps it saturated, but gives you a visual indicator of that as well). A full-strength stannous chloride solution is very good at detecting very small amounts of gold in solution. 

My 'standard' gold chloride solution is a lot stronger than it needs to be, so I occasionally top it off with muriatic to thin it out bit by bit. I should just throw half the bottle (a wee 0.5 fluid ounce dropper) in my next refine and top it off again. I don't use much of it anyway--you really only need to confirm your stannous when you get a negative result and you suspect otherwise.


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## bemate (Oct 15, 2016)

Well, I'll admit I was under the impression that I needed pure tin to get the best results, but pure tin is difficult to find in reasonable amounts for a test solution. But 99,3% Tin solder is a lot easier to find, so that goes on my shopping list for my next trip to the hardware store.


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## bemate (Oct 31, 2016)

A quick follow-up question if anyone takes the time to read and answer: I realize my pins are best suited for a sulphuric cell since they are entirely covered, however, that is not an option for the time being as I have no way of setting up a cell and running it in a safe way. Cyanide is also not an option, both because of the inherent danger, but also due to the legal issues of using it. That leaves me with AP, which is looking to be my most viable option for most of my material. I don't particularly care if it takes a long time, I am not in a hurry, but will the AP be able to get to the base metal of my pins at all? From my small-scale tests, it looks like my pins are copper all the way through, but the gold covers them entirely. From my understanding, that means the CuCl2 will have problems getting to the base metals underneath.

Is it an option to start off the process with an overdose of peroxide to intentionally dissolve some gold to expose copper, and then count on the gold to cement out as the process continues?


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## patnor1011 (Oct 31, 2016)

Use only small bit of peroxide. Get yourself fish tank bubblier that is all you need and patience. Pins will look coppery or dark first but just wait till they completely dissolve. If you want to speed things up little bit search forum for crock pot method.


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## bemate (Oct 31, 2016)

patnor1011 said:


> Use only small bit of peroxide. Get yourself fish tank bubblier that is all you need and patience. Pins will look coppery or dark first but just wait till they completely dissolve. If you want to speed things up little bit search forum for crock pot method.



That was my original plan, I'll just stick with that then. I'll add some premixed CuCl2 -solution as well, I have some pure salt.

Thanks!


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## FrugalRefiner (Oct 31, 2016)

bemate said:


> That was my original plan, I'll just stick with that then. I'll add some premixed CuCl2 -solution as well, I have some pure salt.


If you're going to add some CuCl2, you don't need any peroxide. The purpose of adding peroxide at the beginning is to oxidize a bit of the copper to get the process started. HCl won't dissolve copper, but it will dissolve copper oxide, so the peroxide oxidizes a bit of the copper, the HCl dissolves the copper oxide and creates CuCl2. The CuCl2 then oxidizes more copper and the process continues.

Dave


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## johnny309 (Nov 1, 2016)

Old pins like that?
Deep colour..... no sign of Ni......layer barier is often Pd/Ag......95/5....or 90/10.....
Be aware of Be..... is added to ensure the "elasticity" of those pins .
I use a flat screw driver ....just in the middle of the connector....is fast for me.
P.S.:the windup wire in the connection is copper plated with Ag.


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## jason_recliner (Nov 1, 2016)

bemate said:


> ...will the AP be able to get to the base metal of my pins at all?


Yes.



> Is it an option to start off the process with an overdose of peroxide to intentionally dissolve some gold to expose copper, and then count on the gold to cement out as the process continues?


I can see what you're thinking. And while it would occur as you say, it's not necessary.
CuCl2 will penetrate and undermine the gold layer. If you have plenty of time, don't let apparent inactivity undermine your patience. And for obvious reasons, once it eventually starts visibly, it will accelerate.


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## bemate (Nov 1, 2016)

johnny309 said:


> Old pins like that?
> Deep colour..... no sign of Ni......layer barier is often Pd/Ag......95/5....or 90/10.....
> Be aware of Be..... is added to ensure the "elasticity" of those pins .
> I use a flat screw driver ....just in the middle of the connector....is fast for me.
> P.S.:the windup wire in the connection is copper plated with Ag.



I'll keep that in mind, not done reading yet, so I'll make sure to look up the hazards of beryllium (which I would do anyway as I work my way through the safety section...). As for using a screwdriver, I assume you mean to score the surface to expose the copper? With 1800 pins that is not a very appealing prospect... ;P

Judging from outside temperatures and so on, I will probably not start this up until late April anyway.


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## nickton (Nov 7, 2016)

wouldn't reverse electroplating be the best method for these? Oops I just noticed you posted you can't do a sulfuric cell for some reason. Sorry.
:mrgreen: 
:?:


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## jason_recliner (Nov 7, 2016)

bemate said:


> Judging from outside temperatures and so on, I will probably not start this up until late April anyway.


Do yourself a favour. Throw them in a bucket now, covered with with 2 parts HCl to 1 part water. Regardless of the Norwegian weather of which a Melburnian like myself has utterly no comprehension, they'll likely be ready (or close to ready) by April. Even if they're not entirely decomposed, the outer layer of base metal will be so rotten that the gold plating will flake off when you rattle it around.

Ensure that you have a loose fitting lid, to impede dirt ingress and to prevent pressure build-up. I use a tight fitting lid that I pierced in three places (I like redundancy).

Which brings me to my tip to the frugal: My local Dairy Bell (ice-cream shop) sells empty 11 litre buckets with tight (but soft and stabbable) lids for around 40c each. Actually I paid $1.70 for four. Last time was $1.10 for three. How they calculate it I cannot fathom and I have I little confidence that the 16 year old kids running the shop know what they're doing. But in any case, it's a good deal.


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## bemate (Nov 7, 2016)

jason_recliner said:


> bemate said:
> 
> 
> > Judging from outside temperatures and so on, I will probably not start this up until late April anyway.
> ...



I see your point, but the idea of digging the container out of the snow every few days to check that it has not frozen solid and cracked does not appeal very much to me...  Typically, we will have somewhere from 30cm to 1,5 meters of snow building up through the winter, and having a can of strong acids somewhere inside a pile of snow is not within my idea of safe handling, especially with my kids playing in the snow.

But I will start it earlier than April if we have a spring thaw, so even early March might be viable, but we'll see.


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## jason_recliner (Nov 7, 2016)

Well my friend, you know your area and I do not. So advice is only that.
I thought HDPE could withstand -40°C (or -40°F, if you prefer) continuously. Just how cold does it get where you are?!
(I ask this from a zone that sometimes reaches the despairing depths of -2°C in July)


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## bemate (Nov 7, 2016)

jason_recliner said:


> Well my friend, you know your area and I do not. So advice is only that.
> I thought HDPE could withstand -40°C (or -40°F, if you prefer) continuously. Just how cold does it get where you are?!
> (I ask this from a zone that sometimes reaches the despairing depths of -2°C in July)



Usually we have nighttime temperatures ranging from -5 to -15 from mid-December through to mid-March, with occasional warm weather around 0 and cold spells down to maybe -25 in the extreme. I have no doubt the plastic will hold up, I was referring to the risk of ice expanding and cracking the container, not to mention the risk of puncturing it with my snow shovel... But just as much it comes down to me not wanting to spend more time outside to check my air bubbler or anything more than I need to. I plan to use the cold months to collect gold-bearing scrap and educate myself, building the equipment and planning, and then starting up the chemical processing once it's getting warmer and more pleasant outside, at least for my first few runs.

I only do this for fun, and frotbitten fingers are not on my list of fun things.


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## macfixer01 (Nov 11, 2016)

upcyclist said:


> I would use known, clean ingredients for a test solution like that. I would not go with 'I think it's mostly tin chloride'. Get yourself some lead free sinkers or something like that, and use those.
> 
> Sent from my SAMSUNG-SM-G891A using Tapatalk




Lead free sinkers are likely mostly bismuth, and very little tin if any?


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## upcyclist (Nov 11, 2016)

macfixer01 said:


> upcyclist said:
> 
> 
> > I would use known, clean ingredients for a test solution like that. I would not go with 'I think it's mostly tin chloride'. Get yourself some lead free sinkers or something like that, and use those.
> ...


Around here (US), they're tin. I bought some lead-free sinkers from Walmart and they work like a charm. 

Sent from my SAMSUNG-SM-G891A using Tapatalk


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## bemate (Nov 24, 2016)

Brief update:

I have processed the small batch of pins with solder in HCl/H2O2, partly because I got impatient, and partly to look at some related issues, see: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=39&t=22918

The process worked quicker than expected, and it took only a few days for the acid to eat through the pins, leaving the expected mix of Gold foils, solid AgCl and whatever else came out of the solution and stuck in the filter.

Testing with Stannous showed me I have not dissolved any Gold, so that is the first hurdle safely navigated, now my filters are sitting in a beaker waiting for AR tomorrow.

This should give me a rough idea of the gold content in my pins, though I forgot to count the pins beforehand, so I don't know the exact amount of pins to calculate yield from, and the solder throws my figures off if just going by weight, but it will give me some ballpark numbers.

Will be back tomorrow with some pictures.


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## bemate (Nov 30, 2016)

Well, my gold is now safely in a filter, though not quite the purity I'd hoped for, it's a rather dark brown. Not that it matters terribly much, I think I'll group my various filters with dropped gold at some point and do a re-refining to make sure my first button is nice and shiny...

So, the numbers. My first batch of pins consisted of the 67 or so grams of pins with solder and wire. While I have no accurate number of pins, I would estimate about 25% of that weight to be solder and wire, so about 50 grams of pure pins. That comes down to about 150 pins, that gave me around 250mg of gold in the filter. Rounding down to err on the side of caution, that means in the region of 3 grams of pure gold in my total batch of 1800 pins, slightly below my estimate of 5 grams calculated from surface area and an assumption of 30 microinches plating thickness, but not too bad.

Of course, there are numerous (non)educated guesses in these numbers, but the proof will be in the pudding/button/filter when I get to scale up and do my large batch of pins come spring.

My Auric Chloride after filtering:



And after adding SMB:


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## jason_recliner (Nov 30, 2016)

Good job. The clarity of the solution and the in-progress precipitation look appropriate for a first refine off pins.

If it appears too brown to you, it's to your credit. I say that because some have melted their dark brown powders only to achieve a dark brown splat... and wonder why. You will be amazed the colour that will wash off your powder with HCl rinses, and then a second refine should return you an encouragingly paler result.

Finally, and this is not intended to be condescending, but as you gain experience strive to do this using less and less solution. Remember how much acid Ms Hoke wrote is required to dissolve an ounce.

Hooked yet?


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## Tzoax (Nov 30, 2016)

bemate said:


> Brief update:
> The process worked quicker than expected, and it took only a few days for the acid to eat through the pins, leaving the expected mix of Gold foils, solid AgCl and whatever else came out of the solution and stuck in the filter.


I would suggest incineration of remaining solids in filter paper/HCl simmer boil for removing tin because of possible gold particles trapped with tin oxide.


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## bemate (Nov 30, 2016)

jason_recliner said:


> Good job. The clarity of the solution and the in-progress precipitation look appropriate for a first refine off pins.
> 
> If it appears too brown to you, it's to your credit. I say that because some have melted their dark brown powders only to achieve a dark brown splat... and wonder why. You will be amazed the colour that will wash off your powder with HCl rinses, and then a second refine should return you an encouragingly paler result.
> 
> ...



Thank you, and no, I don't find any of this condescending, while I'm pretty confident in my lab chemistry skills, I realize I'm still a more or less complete novice in this game.

As for the powder, I have a reference sample of dropped gold from some chemically pure gold salts (see my profile pic), and they are a very light brown, and I assume that is gold in the order 4-5 nines since it originally was sold to be used for making gold nanoparticles used in electron microscopy of cell organelles. That serves as my reference as to how the gold 'should' look before attempting a melt. And in any case, I only have about one gram of precipitated gold in total so far, so I'll store them and collect them to a bigger button first.

The volume is very large, I'm aware of that. This is mostly due to two facts: when I started off with my filters from the first drop, I just poured in enough HCl to cover them, I didn't think about them dissolving and making more room in the beaker, and then, when I was filtering, I washed with a lot of water to get all the yellow colour out of the filter with the pulped filters from the AR, effectively tripling my volume after adding ice to cool the solution to precipitate out any AgCl or PbSO4. The filters are safely tucked away in a box with some other filters containing the precipitated AgCl and any gold remains. I will build up that stockpile a bit before I burn and process them, I don't see the point in doing a recovery from just one or two filter papers.


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## Tzoax (Nov 30, 2016)

bemate said:


> The filters are safely tucked away in a box with some other filters containing the precipitated AgCl and any gold remains. I will build up that stockpile a bit before I burn and process them, I don't see the point in doing a recovery from just one or two filter papers.



I suggest that when processing copper/brass based pins with A/P method, always incinerate all that was left in filter paper along with gold foils , simmer boil with HCl, filter, BEFORE processing with AR. Of course, it works on many ways, but this way several things are accomplished:
- your result will be more accurate
- you will get rid of almost all of the tin. When processing pins (that contains tin) with A/P method not all of the tin goes in solution (stannic chloride), some of the tin will form tin oxides (like in this picture) that will trap the gold. When you incinerate the tin oxide, it will go to metal form, and then you can get rid of tin by simmer boiling it in HCl - the tin will go into solution as stannic chloride and it will free the gold so the AR could react with it.
- by incinerating you will get rid of all organic impurities before AR
- you will avoid possible formation of colloidal gold
- your AR solution will be smaller volume
- the gold will drop faster

If i am wrong, please someone correct me.


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## bemate (Nov 30, 2016)

Tzoax said:


> I suggest that when processing copper/brass based pins with A/P method, always incinerate all that was left in filter paper along with gold foils , simmer boil with HCl, filter, BEFORE processing with AR. Of course, it works on many ways, but this way several things are accomplished:
> - your result will be more accurate
> - you will get rid of almost all of the tin. When processing pins (that contains tin) with A/P method not all of the tin goes in solution (stannic chloride), some of the tin will form tin oxides (like in this picture) that will trap the gold. When you incinerate the tin oxide, it will go to metal form, and then you can get rid of tin by simmer boiling it in HCl - the tin will go into solution as stannic chloride and it will free the gold so the AR could react with it.
> - by incinerating you will get rid of all organic impurities before AR
> ...



Thanks for the advice, I'll keep it in mind when I do the bigger lot later on. It will be easier to take care of the incineration when the temperature outside is better as well. I'm thinking of just building my stockpile through the winter and then have an incineration-day come spring, to do all my various filters, chips and contacts in one go, then go back to the chemistry and recover/refine my gold.

As an aside, here is the difference in color from my pure gold and the latest drop from the pins as described above:



As you can see, the one on the left appears almost black because of the flash, but it's a dark chocolate brown in reality.

Edited to fix typo


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