# Silver contacts dissolution problem.



## Tndavid (Sep 4, 2016)

Cannot get them to dissolve. 5 or 6 cut close to contact. Added appr. 25 ml distilled h2o, 50 ml hno3 that I made in accordance to an instructional vid on YouTube by nurdrage I believe. Put on medium low heat. Process started well, nice reaction with green coloration. Suppose that was the copper. Then it darkened and stalled. Extracted 1 to check and contact still there. Added 20 ml h2o, 9 ml hno3, 18 ml hcl. Now just a minor reaction. Still dark green solution. Any help would be appreciated. Thanks.


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## g_axelsson (Sep 4, 2016)

If you have some chloride in the water or acid it could create a crust of silver chloride and the dissolving stops.
Some silver contacts is made up of silver and sintered tungsten. You can dissolve the silver out of them but it will take time.
There is a lot written about it on the forum.

Nitric acid dissolves silver but it prefer to digest copper or brass first and that can deplete the acid. If it doesn't dissolve the silver then it is either a problem with your metal or the acid. 

Göran


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## Tndavid (Sep 4, 2016)

Ok thanks. Possibly another method? Perhaps HCL and KNO3?


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## Tndavid (Sep 4, 2016)

It just doesn't look like enough base Metals were dissolved to deplete the acid. Maybe 1 of my younguns put tap water in my distilled bottle. Would the chlorine in tap crust it over like you mentioned? The contacts themselves look clean as far as their silver coloring.


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## Tndavid (Sep 4, 2016)

And also there is some dark colored debris in the bottom of the beaker..


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## Smack (Sep 4, 2016)

Where in your reading did you read to add HCL when trying to dissolve silver?


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## Tndavid (Sep 5, 2016)

It was a random post I came across before I joined this forum. Supposedly if the solution was saturated. I think they was all mixed up.


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## Topher_osAUrus (Sep 5, 2016)

If you add HCl and KNO3 in the right stoichiometric amounts, it will make HNO3, but, there will most likely be residual chlorides.

If you made your own nitric to dissolve the contacts, depending on the methodology, there will most likely be left over chlorides or sulphates that can each cause their own problems with dissolving silver.

Chlorides make silver chloride, which can create an impervious layer preventing further dissolution.

Sulphates will make silver sulphate, which is blackish.

When doing silver contacts, its better to use nitric that is free of both, so you dont have unwanted hitchhikers with the silver cement.


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## johnny309 (Sep 5, 2016)

Maybe ...and without picture of the original material,is not a sure thing....but I"ll guess ...too much Zn....If you want help.....we are not on "the wild guess show"....so...provide a little info,as:
1.picture of your start material
2.picture of the solution.

P.S.: when you try to help someone ....you got to know why...and how....... but ......if he or she is unwilling to cooperate ..... just a waste of time .....


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## g_axelsson (Sep 5, 2016)

Topher_osAUrus said:


> If you add HCl and KNO3 in the right stoichiometric amounts, it will make HNO3, but, there will most likely be residual chlorides.


Like all of it! The chloride from HCl doesn't disappear.

In the same way you can add KCl + HNO3 and get hydrochloric acid.

But both examples are a lot simplified. The Cl and NO3 is not joined with H or K in a chemical bond, they all exist as ions dissolved in the water.

Göran


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## Topher_osAUrus (Sep 6, 2016)

Thanks Göran.

I was trying to get the point across as clear and simple as possible...but, doing that can lead to confusion.

I agree with Johnny, that it's really nothing but a guessing game without all of the facts and some pictures to help along the way.
But, like a puzzle, little tid bits of information can slowly build up to see what is really happening, but its still nothing more than conjecture.

Really, the only way to get rid of those chloride or sulfates, is distillation...careful distillation.. And, as the majority here know, distilling is an artform all of its own, and is no simple task.
All it takes is to be a few degrees off and those chlorides you are trying to remove from the nitric, end up getting carried over...even if you are VERY careful, its still difficult to remove them all.

The simplest...fastest...SAFEST way to go about it..

Buy your nitric for silver from a reputable dealer... And save the "mickey mouse nitric" (as gsp called it.. lol), for other things.


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## Tndavid (Sep 11, 2016)

I appoligize for not adding pictures. I just put them away in a covered beaker until later on.


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## Topher_osAUrus (Sep 11, 2016)

Wise decision, but still, pictures would definitely help everyone figure out whats going on.

Hopefully you didnt mix HCl with your nitric/water, because that would make the silver precipitate as silver chloride.

The KNO3/HCl is a "poor man nitric" method, and if you are using real nitric, dont mix them.
The contacts probably stopped dissolving because the remainder of what you see is tungsten. (the black you see on the bottom hints at that) The green color is copper nitrate with free nitric in solution.

If you can smash them in your fingers they are most likely fully dissolved (wear gloves, of course).
If not, they are still holding some silver. (again, a guess without a picture, assuming they're W/Ag contacts)
Tungsten/silver contacts are one of the few things you truly *boil* when working with acids. And a great deal of care must be taken. 

Use a watch glass, also use a pyroceram catch pan between the burner and beaker. Boiling acids is very dangerous if improperly done. It's also wasteful, as the high heat kills the acid, making the NOx gasses evolve more than usual from decomposition.

Adding just a dash of H2O2 can help keep the nitric from gassing off.

But, then again, without seeing them, it could be a crust of AgCl blocking the acid from getting to work...


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## Tndavid (Sep 13, 2016)

Thanks for all the advice Topher. I will post pictures before I restart the project.


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