"Gold" plated pins - no gold/plated with different metal ?

[orvi]

Hi
today, I experienced something very strange. Batch of male pins from old (at least late 80´s) connectors (TESLA brand, made in Czechoslovakia). WK type. Looking very good, nicely golden. As they were mounted in connectors, they have copper "skirt" which fits the pin into the hole.
I had no doubt that it would be great recovery, pins from that factory never ran below 4-5g/kg. I had 285 g prepared. Routine, as usual, dissolving in AR, denoxing with sulfamic, cooling, filtering and precipitation with sulfite. No big deal... As I done it like hundred times before.
Pins started to dissolve nicely, near the end, lots of the "empty" foils floated to the top, everything as usual. Retaining golden colour and luster even they were in AR.

But, 1 hour after the "drop", no gold, no signs of precipitate nor cloudiness in the solution. Just transition from green to classically brown-yellowish, very dark liquid. Shining the light from under revealed no speck of precipitate after first additions. Testing with stannous negative (to everything, not only gold) - but that could one expect after pouring like 7 teaspoons of sulfite (in panic over the missing gold ) to the 2 liters of denoxed AR solution After 3 more hours sitting, no cloudiness at all, just bunch of white junk precipitated - from excess use of sulfite. I let it covered and sitting overnight. We will see if there would be something in the morning.

My question is:
Is there any possibility that completely ordinary "golden looking pins" are plated with some other metal ? Because it wasn´t brass, I am sure. I added pictures below. Material was manufactured likely between 60´s and 80´s. Now I am not only concerned about missing gold, but possibly some unknown stuff containing some toxic junk, like beryllium.
From modern stuff, I know that there could be nickel plating. But it will definitely not survive in warm AR while retaining the golden luster.

Now, I am clueless. If I did something wrong, or the pins contained no gold at all... Everything should be in the solution, I even have the filter paper from filtration, but only a trace of white residue (probably Pb/Ag salts).

 

[Martijn]

Did you do a stannous test before the drop?

And maybe try to cement anything out of solution on copper.
The cloudyness may settle after a few days.
How much solution do you have? You're expecting about one gram of gold, right?
It might be still floating around.

 

[orvi]

Did you do a stannous test before the drop?

And maybe try to cement anything out of solution on copper.
The cloudyness may settle after a few days.
How much solution do you have? You're expecting about one gram of gold, right?
It might be still floating around.

No. I do this numerous times a week. Everything gone into the solution, I worked it up as I regularly do. I should be more strict on testing, but I have done this process so many times, that in rush, I forget to do it. If I didn´t forget, everything will be solved... One mistake, precisely timed

I tried to stick a copper wire to the small portion of the solution, but apparently nothing really happens. Makes sense due to negative stannous.

I will expect 1-2 g in 2 L of solution. I am really curious what I find tomorrow.

 

[Martijn]

That's typical. The one time you skip a small check step it goes wrong. Well, another mystery to try to solve and learn from!
I still think its gold, because brass or other base metal foils would have dissolved along with the copper being about as reactive as the base metal.
To be honest, i hardly ever check for gold in solution when i know i dissolved gold.

I replied to your post because I just processed some copper cell slimes and AP foils and dust.
Stannous was negative after SMB, washes also went in the solution, the solution was clear but kind of dark colored still.
Added a piece of copper and now I have a powdered bottom in a 2L beaker. Curious to see what's there. If there are any pgm's maybe.
The stannous was verified with gold test solution.
I guess small amounts can hide in between the other atoms
Amount dropped with SMB was 2.2 grams, I think another 1.5 gram fell out on the copper (or from coalescing nano particles)

Time will tell. So, did you find a brown layer in there this morning?

 

[kurtak]

To be honest, i hardly ever check for gold in solution when i know i dissolved gold.

To be honest - same here - I rarely if ever test when I know I put gold in solution - I only start testing after starting precipitation to insure when precipitation is completed

orvi - Hmmm - crazy - makes no (common) sense - so might have to think outside the box

Possibility (outside the box) --------

Negative SC test "after" SMB - & - no indication of cementing with copper --- so possibility ---------

You precipitated gold colloids (for reasons only the gods of chemistry know)

Oppps - hit send before finishing - so edit to finish

A test I would try - take a sample (50 - 100 ml) of your solution - add some nitric (should already have enough HCl) if there is gold colloids they should redissolve - test with SC

If no positive (SC) result add some more HCL - test again

Let us know what happens

Kurt

 

[kurtak]

Had to edit my last post - just letting you know in the event you read it before I reposted with the edit

Kurt

 

[orvi]

That's typical. The one time you skip a small check step it goes wrong. Well, another mystery to try to solve and learn from!
I still think its gold, because brass or other base metal foils would have dissolved along with the copper being about as reactive as the base metal.
To be honest, i hardly ever check for gold in solution when i know i dissolved gold.

I replied to your post because I just processed some copper cell slimes and AP foils and dust.
Stannous was negative after SMB, washes also went in the solution, the solution was clear but kind of dark colored still.
Added a piece of copper and now I have a powdered bottom in a 2L beaker. Curious to see what's there. If there are any pgm's maybe.
The stannous was verified with gold test solution.
I guess small amounts can hide in between the other atoms
Amount dropped with SMB was 2.2 grams, I think another 1.5 gram fell out on the copper (or from coalescing nano particles)

Time will tell. So, did you find a brown layer in there this morning?

To be honest - same here - I rarely if ever test when I know I put gold in solution - I only start testing after starting precipitation to insure when precipitation is completed

orvi - Hmmm - crazy - makes no (common) sense - so might have to think outside the box

Possibility (outside the box) --------

Negative SC test "after" SMB - & - no indication of cementing with copper --- so possibility ---------

You precipitated gold colloids (for reasons only the gods of chemistry know)

Oppps - hit send before finishing - so edit to finish

A test I would try - take a sample (50 - 100 ml) of your solution - add some nitric (should already have enough HCl) if there is gold colloids they should redissolve - test with SC

If no positive (SC) result add some more HCL - test again

Let us know what happens

Kurt

Yep, it goes with time... You see the pins, you see gold, you dissolve everything... So gold is in solution, there is nowhere else it could go. I will probably start to test it more frequently

The solution of the mystery will be probably compilation from all bits you guys suggested.

In the morning, precipitate on the bottom was snow-white like in the evening. But new layer of greyish coloured crystals appeared on top. After decanting, I found miniscule ammount of gold nanopowder mixed with seemingly some PbCl2 or other sparingly soluble stuff (soluble in HCl).
After washing out the junk, I was left with 0,31g of gold powder... So from here only assumptions I could make:
1. pins were unusually low grade, less than 1,5g/kg
2. gold is in the form of colloid or extremely fine particles that didn´t settlet overnight = still in the solution settling.
3. nano-gold colloid was formed, that never settle to the bottom
4. because I didn´t smelled SO2 from the solution in the morning, it is possible that some "funky redox stuff" was going on despite de-noxing, and some of the gold is still in the solution. It´s 2 L of the juice, some 0,1-0,2g of gold could easily hide. Dilution is also a reason why I firstly didn´t tested the solution after "redissolving" the assumed colloid.

I treated the pot with another tablespoon of SMB after decantation, and I will let it sit for whole holidays I am very curious what will I find tuesday next week.
If nothing will appear, I will oxidize the whole pot with some nitric or chlorine and try to cement the remains on copper. We will see what else is hiding inside

Good lesson learned: You may do the same work 100 times, but 101st time it will go completely strange and you could be lost even with copious experience.
Definitely worth remembering gold could be forming particles for hours and even more. In the past, I experienced situations when the gold settled for more than a day. But cloudiness was immediately visible.

Thank you for the suggestions. And also for the knowledge I am not the only one who do not test 100% of the time

 

[orvi]

Investigation could continue, but I need your opinion on my thoughts
When I was pulling the pins out of sockets, I remember that one piece gone flying around somwhere in the room. I realised that one piece is the only one living evidence what was in the actual material before digestion and precipitation possibly gone wrong...
Long story short, I spent 15 minutes kneeling on the ground, but I found it

So I have one original pin, weighing 0,18 g not a representative sample, but it´s something. I would like to know very roughly how much gold these pins were running. Approx, if it was 1g/kg or 3g/kg etc.

I think of dissolving base metals in nitric, and then the gold foil, i have figured out two options:

1. dissolve the foil in AR to the exact volume, denox, than prepare standard gold solutions of known content of gold per volume, and compare their stannous chloride results

2. take the foil to the melt dish, melt it into the miniscule bead and measure its diameter

Which of these you would do ? Or is there some simple DIY assay-like method which could tell me ?
Thanks guys

 

[kurtak]

1. dissolve the foil in AR to the exact volume, denox, than prepare standard gold solutions of known content of gold per volume, and compare their stannous chloride results

I don't really think that is going to tell you much - other then that you have dissolved gold

2. take the foil to the melt dish, melt it into the miniscule bead and measure its diameter

your best bet (other then scale that will measure mg)

Or is there some simple DIY assay-like method which could tell me ?

dissolving the base metal away with nitric to get the foil should (also) give you "somewhat" of an indication

1) nitric reacts with base metal almost instantly & foil falls apart to small flakes = flash plate = very low yield = less then gram per pound

2)nitric reacts with base metal relatively quick foil doesn't fall apart but is light & floaty = fair yield = gram plus per pound

3)nitric takes a bit of time getting under foil before reacting with base metal & foil somewhat retains shape , moves but not real floaty = good yield = 2.5 - 3 grams per pound

4)nitric has hard time getting to base metal - may need boiling to rid base metal - foil looks just like pin - needs crushing to tell if base metal is actually gone & sinks like rock to bottom of beaker = great yield = well over 3 & likely headed to 5 grams per pound

Or X2.2 above for kg

I will often do the above test on just one pin - when I "know" the batch is all from the same source just to get an idea of expected yield

Kurt

 

[orvi]

I don't really think that is going to tell you much - other then that you have dissolved gold

your best bet (other then scale that will measure mg)

dissolving the base metal away with nitric to get the foil should (also) give you "somewhat" of an indication

1) nitric reacts with base metal almost instantly & foil falls apart to small flakes = flash plate = very low yield = less then gram per pound

2)nitric reacts with base metal relatively quick foil doesn't fall apart but is light & floaty = fair yield = gram plus per pound

3)nitric takes a bit of time getting under foil before reacting with base metal & foil somewhat retains shape , moves but not real floaty = good yield = 2.5 - 3 grams per pound

4)nitric has hard time getting to base metal - may need boiling to rid base metal - foil looks just like pin - needs crushing to tell if base metal is actually gone & sinks like rock to bottom of beaker = great yield = well over 3 & likely headed to 5 grams per pound

Or X2.2 above for kg

I will often do the above test on just one pin - when I "know" the batch is all from the same source just to get an idea of expected yield

Kurt

Science may be the good starting point, but I see that experience is gonna make it so much easier. And you have plenty of experience, as I see with every post you make. Thank you for the insight, I am definitely writing this up this is a very clever thing to observe, I may do it regularly (after getting familiar with) to examine the material before purchasing the whole lot. This would save me 40 euros this time Luckily, this wasn´t the only item I purchased and still happily in green numbers

I´ve done a quick calculation - 226 connectors x 7 pins = 1582 pins. With now 0,31g gold, that´s roughly 0,2 mg for one pin. I am afraid that I wouldn´t be able to measure it reliably, altough I have access to scales that measure to 0,1 mg. But accuracy is another thing. So probably measuring the diameter will tell me more.

I will go with nitric, observe the behaviour of the dissolution, and save the remains for melting at home.
This will be very interesting, as I´ve done hardly any assay of yield based on bead diameter
Putting me well out of my comfort zone, that´s what I need

 

[Martijn]

With small melts, I always get tiny balls of gold stuck in the crucible. Part sloppiness and part due to small heat source.
So getting a tiny amount like that to coalesce into a single ball will need some extra effort.
Maybe try to roll the foils into a ball or put them in a filter and cut off the end.

 

[orvi]

I certainly test this approach with other pins before I go straight into that one. Good point, that sticking is a real issue. I must read how to do it correctly.
I have practically no experience with proper fire assay, but I read a lot of stuff about it. I have everything for small sample melting, measuring etc. I think that with one afternoon trying to melt the foils from pins should give me some sloppy experience to make the thing and if no... Nevermind, life goes on

 

[orvi]

So, I did the test with one remaining pin... Not worth mentioning very thin plating, flaked off in nitric fairly quickly, and partly disintegrated when swirled around :/ so, not my fault in refining, not some unusual plating, just only low gold
Additionally, I left the beaker with AR solution to sit for one more week after fresh dose of SMB. Another like 70 mg precipitated, the rest was discarded to the waste... So finally around 1,4g/kg.... Shame Paid 57euros for 0,258kg of pins. Happen from time to time

 

[orvi]

But I will cover the loss with another batch where I am certain that good gold is present. Grey socket pins 10+g/kg (female even 14g/kg), green and blue pins 4,5g/kg

 

[jphayesjr]

Yep, it goes with time... You see the pins, you see gold, you dissolve everything... So gold is in solution, there is nowhere else it could go. I will probably start to test it more frequently

The solution of the mystery will be probably compilation from all bits you guys suggested.

In the morning, precipitate on the bottom was snow-white like in the evening. But new layer of greyish coloured crystals appeared on top. After decanting, I found miniscule ammount of gold nanopowder mixed with seemingly some PbCl2 or other sparingly soluble stuff (soluble in HCl).
After washing out the junk, I was left with 0,31g of gold powder... So from here only assumptions I could make:
1. pins were unusually low grade, less than 1,5g/kg
2. gold is in the form of colloid or extremely fine particles that didn´t settlet overnight = still in the solution settling.
3. nano-gold colloid was formed, that never settle to the bottom
4. because I didn´t smelled SO2 from the solution in the morning, it is possible that some "funky redox stuff" was going on despite de-noxing, and some of the gold is still in the solution. It´s 2 L of the juice, some 0,1-0,2g of gold could easily hide. Dilution is also a reason why I firstly didn´t tested the solution after "redissolving" the assumed colloid.

I treated the pot with another tablespoon of SMB after decantation, and I will let it sit for whole holidays I am very curious what will I find tuesday next week.
If nothing will appear, I will oxidize the whole pot with some nitric or chlorine and try to cement the remains on copper. We will see what else is hiding inside

Good lesson learned: You may do the same work 100 times, but 101st time it will go completely strange and you could be lost even with copious experience.
Definitely worth remembering gold could be forming particles for hours and even more. In the past, I experienced situations when the gold settled for more than a day. But cloudiness was immediately visible.

Thank you for the suggestions. And also for the knowledge I am not the only one who do not test 100% of the time

Chemist and electrical engineers in the 80;s and 90s experimented with various coatin and plating processes to help reduce dependence on PMs such s gold. Here's a link to some of that research. Does "colloidal gold" catch your eye? https://www.researchgate.net/public...or_Room-Temperature_Carbon_Monoxide_Oxidation