# dissolving silver?



## Geo (Jul 14, 2011)

will HCL+peroxide dissolve silver?i have many HP boards circa 1970s that are gold plated on all circuits but have a coating of silver over the gold.i want to just place all of them in AP and really not too worried about the silver recovery as long as i can get the gold off.getting the silver back would be a plus but not a high priority.nitric acid would be the best solution but there are so many it would take over five gallons.if anyone can give me some pointers i would really appreciate it.


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## Claudie (Jul 14, 2011)

Can you post a picture of one of the boards? I don't understand why Gold would be covered with Silver.


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## Harold_V (Jul 14, 2011)

Geo said:


> will HCL+peroxide dissolve silver?i have many HP boards circa 1970s that are gold plated on all circuits but have a coating of silver over the gold.i want to just place all of them in AP and really not too worried about the silver recovery as long as i can get the gold off.getting the silver back would be a plus but not a high priority.nitric acid would be the best solution but there are so many it would take over five gallons.if anyone can give me some pointers i would really appreciate it.


It is highly unlikely silver has been placed on top of gold, considering each metal has the tendency to migrate to the other. Did you test with Schwerter's solution to ensure you're seeing silver? I expect that, if anything, the board has been tinned after gold plating. Try dissolving the layer with hot HCl. 

Harold


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## Geo (Jul 14, 2011)

the only test i did was with 50/50 nitric and the reaction was light blue,that's why i suspected silver.after the initial reaction of a few seconds the reaction stopped and you could see the gold color coming through the silver color.the boards are not the boards of modern comps they are a light green color and the circuits aren't uniform,its like each one was custom made.ill post a pic tomorrow as soon as i can locate my cam,my oldest took it camping with him to the river. :lol:


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## Harold_V (Jul 16, 2011)

That, alone, is not a reliable test for silver. Schwerter's solution would be. 

It's pretty simple. There's no good reason for a board to have gold, then to be covered with silver. It simply makes no sense, but tinning does. I expect that you have a tin coating. Apply a drop of HCl and see if it dissolves. Also, try to dissolve a short piece of one of the traces entirely, using a drop of nitric. When you have eliminated everything but the gold foil, add a grain of table salt to the solution. If there's silver present, you'll see the familiar white cloud of silver chloride form. I expect it won't be there. If there's any question, as the solution being somewhat cloudy, add a drop of HCl to the mix. If the cloudiness is lost, you have no silver. 

Harold


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## Geo (Jul 16, 2011)

ive never made Schwerter's solution before.i looked it up online and it says that as it ages it could precipitate a highly explosive compound.i do know that silver does make for some potent stuff and my chemistry is lacking enough that im afraid to try it.the rest of this stuff is dangerous enough.is there another less dangerous test for silver?i do believe you are right about the tin though.i placed a whole board with components still on in a bowl and added enough HCL to cover the board.after an hour the circuits were a black color and after i wiped it off the gold could be seen easily.i figured the black could be the disolved tin or maybe lead.i'll do 10 pounds of stripped boards in HCL with a bubbler and see what happens.i have a good idea its not silver so i wont have to worry about trying to reclaim any silver.thanks for the help.


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## Harold_V (Jul 16, 2011)

I was not aware that Schwerter's solution has the potential to be dangerous. I used it for more than 20 years, and had no problems whatsoever, aside from the odd chemical burn when I got careless and got a drop on my skin. 

You would not make a large volume of this testing solution. When I was actively refining, I'd make only one fluid ounce at a time, and it would last for a VERY long time. The bottle I used to store my solution came with a gold testing kit, a small square container that held just a fluid ounce. It was fitted with a ground glass stopper that had a glass dauber included. A single drop from the dauber is all that is required for a test, so literally hundreds of tests can be performed with an ounce of fluid. 

There are other tests for silver, one of which is to use nitric alone, then to test the resulting solution with HCl or salt to see if there's any silver chloride precipitated. The problem with the other tests is they take more time. Schwerter's yields an instant result, and can even detect silver plate if the testing procedure is correct. I highly recommend you investigate a little more before ruling out its use. 

Harold


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