Where Did The Silver Go?

[burningsuntech]

I'm processing some gold plated Beryllium copper with AP in a 2 liter beaker.
After decanting and pouring off the bulk of the AP, I would pour in some distilled water to wash out the Silver chloride and set that aside.
I believe that it is silver chloride because it starts out as light grey and then slowly turns deep dark purple with exposure to sunlight. Some of the particles of gold end up in the silver chloride solution. To get at these, I add tap water to wash the silver chloride and get a strange reaction. The water turns a cloudy brown (Iron?) and produces a brown precipitate. If I add a small amount of HCl, the solution clears up (acidification?) and only the gold is visible. So I have two questions. What happened to the Silver Chloride? AND How can I recover the Silver if it is in solution which is of a low Ph? Cementation?
Any help would be appreciated.

 

[butcher]

It sounds like you have mostly a copper chloride CuCl powder, you can also have a white powder of lead chloride, if silver was actually involved you could have some silver chloride.

Lets take these white powders, and add some HCl if it goes into solution as a brown liquid it is copper chlorides CuCl and CuCl2 adding air will convert the brown solution to a green solution of CuCl2, Hardly any silver chloride or lead chloride would go into solution, because of their solubility's, so here we can dissolve the copper chloride from our lead and silver chloride powders.

Now we can separate lead and silver chloride by their solubility.

Silver chloride is insoluble in hot or cold water.
Lead chloride is insoluble in cold water but becomes more soluble in hot water (almost to its boiling point).

so if we add hot water we can dissolve the lead chloride, move the soluble lead chloride to a cooling vessel and let the solution cool to precipitate most of the lead salt from the water, we can use the water in two portions one hot dissolving lead chloride while one portion is cooling precipitating its lead salt, then decant and reheat this water to reuse it again to try and dissolve more lead chloride from our silver chloride, eliminating the use of a lot of water which becomes a toxic waste to have to treat and deal with later...

 

[Anonymous]

Butcher's post is spot on.

To add to it, if the white powder is disappearing with HCL then it's a Copper Chloride not Silver Chloride. I've seen exactly the same thing happen when processing fingers in AP. You don't have silver there if the salt is completely dissolving, however I must admit to have been a little foxed when you described the original source material as Gold plated Beryllium Copper and then wondered where the silver was.

Remember you've got Beryllium there too whilst you're cleaning up ok?

I've also processed this kind of material and I had absolutely no silver, lead or tin. However my raw material was in wire form, and I understand that yours may be different

Jon.

 

[Geo]

Most buss material is silver plated to some extent. It can be mistaken for just tin plating sometimes.

 

[burningsuntech]

On reading Butcher's post I realized that I had read this in Hoke's book. But the one thing that made me think I had silver chloride in the first place was that the original powder was a light grey color and it turned dark purple when i exposed it to light. In the case of lead chloride That powder doesn't change color when exposed to light. Also when I ran the first batch of these strips, I got a similar reaction. It seems that these kinds of metals are copper or beryllium-copper plated with silver or nickel then plated with gold. Its a mess to sort out but thanks to Hoke's analysis, easy to separate. I have a pic of the strips with their corresponding plug pins attached for reference. Another thing I notice with this metal is it's color being slightly orange or red and referenced that in an earlier post as indication of heavy gold plating.

Secondly, I believe that the color change I got in the solution is due to the tap water I am using. My tap water is rich in calcium chloride and iron. That could be the reason why the solution changed color to a brown and when I added more HCL changed back to a clear solution which showed only gold particles in it. That's when I noticed that what i think to be silver chloride disappeared. I have since tried using only distilled water for all rinsings on this project and the silver chloride remains.

Now that brings forth a new question. Have I mistakenly found a way to clean up silver chloride from solution to expose only gold that is trapped with it? Don't know. But I'm looking into that more closely from now on. Looks like a water test is in order.

As for the chlorides, it looks like the more I think I know, the less I know. Thanks guys.

 

[maynman1751]

it looks like the more I think I know, the less I know

That's pretty true for a lot of us!!!!! :roll:

 

[nickvc]

Gold plating over silver is not usual as the metals can migrate but it isn't unheard of, the usual substrate is nickel.

 

[Geo]

If you have access to some nitric acid, try dissolving one in just nitric acid and see what you can do with the solution. There are a couple of test with just nitrates that's easy enough to do that will tell you something.

 

[Anonymous]

My experience of that mix of gold and beryllium so far as been as an alloy not a plate. The colour was the same as the picture you showed. Are you 100% sure that it's plated?

It was used extensively by a number of major enterprise telecoms/mid range/mainframe server manufacturers to provide a link between flat pin processors and gold contacts on a main board. I found this out the hard way because I used to throw the things away until someone on this forum pointed out the error of my ways and the high gold yield. Then I did a whole lot of reading up on the subject.

Do yourself a favour and make sure that before you attempt to melt the gold you've refined it well, if not twice so you have absolutely no Beryllium in the crucible. It doesn't play well with humans.

Regards

Jon

 

[g_axelsson]

Jon, are you talking about the fuzz button that's used to connect some pinless CPU:s to the board?

I would be very surprised if any contacts were made from a copper beryllium gold alloy instead of gold plated copper beryllium alloy. There is no technical reason to put gold into an alloy and not on the surface where the properties of gold is needed.
http://www.custominterconnects.com/fuzzbuttons.html

Göran

 

[goldsilverpro]

I agree with Goran.

I have only seen alloyed gold used in electronics in a few cases: Au/Sn, Au/Si, and Au/Ge brazes and certain connectors on old Burroughs mainframes that have very small 75Au/25Ag points on the contact area of the pins. Besides the small amount (about 1% max) of Ni, Co, or In added to gold plating to make wear surfaces harder, the only alloyed plating I've seen was a white 60Au/40Pd alloy on reed switches and I only saw that once.

According to the link Goran gave, the fuzz buttons are gold plated BeCu, at least those made by that particular company. If that worked for one company, it would work for every company making them. I think the fuzz button's main purpose is to provide good electrical conductivity between 2 surfaces. Reasonably thick, nearly pure (or, pure) gold plating would likely provide much better conductivity than a Au/Be/Cu alloy. I see no technical reason why the alloy would be used. I would certainly wager against it happening.

If you dissolve a little fuzz in nitric, I would bet the remaining gold would contain some bright and shiny flakes, indicating it is plated. If it were an alloy, the Au would end up in the form of a dark dull powder, with zero shininess unless it were burnished.

Alloys of Au and Be are extremely brittle and non-ductile. The fuzz has to be somewhat ductile and springy so it will continually conform to the surfaces. I just read a patent that alleviated the brittleness problem by combining Be and Au powders together and then compacting these in the shape of the desired part, similar to the way they make W or Mo parts. The fuzz is made from fine wire which would have to be pulled though dies. Be/Cu is ductile enough to pull the wire but I doubt if it could be done with Au/Be/Cu.

There's one helluva lot of gold surface area on those "fuzz" things. This could make for a helluva lot of gold per unit weight, even with normal or thinner Au plating thicknesses.

Jon,
You said you researched this thoroughly. Can you provide any reliable reference that states a Au/Be/Cu alloy has ever been used in electronics?

 

[g_axelsson]

burningsuntech, what is the size of that plug board on the picture? I think there is a bit of confusion in this thread and the late discussion about fuzz buttons isn't the same as the plug board you have.

The plug boards I have seen was a row of silver plated brass conductors in one layer and another row of conductors crossing the first one in another plane. By plugging a pin in a position you made contact between one column and a row. Is that what you have?

Göran

 

[Anonymous]

Chris the short answer is I cannot.

My comments were poorly worded and easy to take out of context as it appears. The "whole lot of reading up" I did was on the use of the Gold/Beryllium wiring not on gold/Beryllium alloy. Mainly because I was incensed at having thrown away hundreds of the fuzzies after being told be a jeweller that they were rubbish prior to joining GRF . I was then told that the fuzzy wires were an alloy by an engineer and that looks to be hogwash now doesn't it?

If I've dropped the ball then my apologies- I've got broad shoulders I can handle a slap round the chops mate. 8) 8)

Incidentally a fully populated fuzzy from a Sun server yields 0.11g per unit. I've now run hundreds successfully after my rocky start. So I agree the surface area helps to get a marvellous yield.

On another though note I'll have disagree with you and add to your list of gold alloys in electronics 8)

I have refined 35%/65% Gold/copper alloy sheet (not plated) for use in producing aerospace electronics boards. It's a strange colour and would be passed off as copper unless one knew what it was. I know it was this alloy because I had the manufacturer's data with the product. I MAY have a picture of it somewhere and if I can find it I'll gladly share.

Jon

edit: I had the percentages the wrong way round on the gold/copper alloy

 

[Anonymous]

Not a great picture but it shows the colour of the alloy, although it's definitely redder "in the flesh."