Au plated & Ag plated

[Geld Konig]

I know that a piece of Au plated is easy to discover by using HNO3 that "eat" the piece and rest a fine slice of Au. if the piece is whole made of Au ( Au 18 K or other less K) the action fo HNO3 is none or very little.
Is there any way to know if a piece of Ag is plated or it is a whole piece( silver alloy)? HCl make this? And if the underlie of Ag plated is copper? so the HCl no react.Is there any method to know this?

 

[qst42know]

If you can dissolve some in nitric acid and then add a drop of HCL the white solids would be silver chloride.

Or dissolve a small sample in nitric and add some clean copper and observe the cement silver.

All of this assumes you can damage the original piece.

 

[lazersteve]

Schwerter's solution is the standard test for silver items.

Here’s how to make Schwerter’s Solution and test for Silver and base metals with it:

1. Dissolve Potassium Dichromate salt in 8mL of distilled water in a glass container. Add crystals until no more salt will dissolve in the liquid.
2. Add 25mL of 70% Nitric Acid
3. Store in a small bottle.

Edit: File a deep notch in the area to be tested.

Apply a drop of Schwerter's Solution to the test piece.

The color reaction of the solution with the metal will be as follows:
Brass - Dark Brown
Copper - Brown
Nickel - Blue
Palladium - None
Gold - None
Silver Pure - Bright Red
Silver .925 - Dark Red
Silver .800 - Brown
Silver .500 - Green
Lead - Yellow
Tin - Yellow

Steve

 

[Platdigger]

a file

 

[qst42know]

I need to get some potassium dichromate.

And as always a reasonable source of nitric.

 

[Harold_V]

I'm not sure, but I think you guys missed his question. I understood it to be if there is a way to test silver that may be plated, with a copper or nickel base metal.

If that's the question, then the answer is yes. A file is very much a part of the test. A notch should be filed, deep, in the piece in question. A drop of nitric should then be placed in the filed notch. If the item is silver plated, a distinct blue reaction will result. If it is silver, even alloyed, coin or sterling, the notch will not yield a blue color, and the silver will shift to a rather interesting cream color.

If Schwerter's solution is used for the test, you must still file a deep notch. to insure that if the piece is plated, you get past the plating. Schwerter's will still react red, but given a little time, the core will alter the display, shifting the red color to brown or even green.

Harold

 

[Geld Konig]

The question are: the piece is or not silver plated? I think a sulution of NaCN in eletricity and the Ag piece in a cathode will take all silver if she is under lye by a niquel. Is there another method like we can do with gold plated object( using only HNO3)?

 

[steveonmars]

Steve,

I see Potassium Dichromate listed on ebay. It doesn't say "salt", is this the same thing I need? They're selling by the pound, I imagine that'll last the rest of my life.

Thanks,

Steve

 

[lazersteve]

Steve,

It is a salt of potassium and chromic acid. Therefore it should be purchased in solid form.

Steve

 

[kmggold]

The best way I've found to test for gold plated and silver plated items is to use undiluted nitric acid.
Make a deep scratch in the item if possible, and place a drop of nitric on the scratch.
The scratch made in gold filled and gold plated items will turn green and show fizzing and small bubbles within the scratch. The gold surrounding the scratch will remain undisturbed with no discoloration. Low karat gold may tarnish turning a light brown tea colour. A reaction to the alloy metals within the gold.
The scratch on electroplated, HGE, GE, gold items will fizz violently, emit brown to black smoke and consume all the gold plating, leaving the spot where the nitric acid was applied, bare copper or brass.
Silver plated items show the same results as with gold plated items. The thickness of the plate will determine how much fizzing and smoke there is. Thicker plate equals less fizzing.
Thicker silver plated items will react the same as thick plated gold, whereby the scratch will turn green, fizz and have bubbles, but the silver surrounding the scratch will turn a cloudy cream colour. The drop of acid will show a precipitate in it that resembles curdled milk within the clear fluid. Once the acid is removed using water, the silver will remain a cloudy cream colour.
Schwerter's solution, which as lazersteve writes, is made:
1. Dissolve Potassium Dichromate salt in 8mL of distilled water in a glass container. Add crystals until no more salt will dissolve in the liquid.
2. Add 25mL of 70% Nitric Acid
3. Store in a small bottle.
You may use any grade of nitric acid you can find. Technical grade, reagent grade, and laboratory grade are all equally fine. All you need is pure nitric acid which typically has an assay purity of 68-72%.
You only need 1-1.2 grams of Potassium Dichromate.
Testing silver plated items with Schwerter's solution may give confusing colourimetric results depending on the thickness of the plate. If the plate is thick, you may get blood red precipitate in the acid from the silver that bleeds into the brown within the copper or brass in the scratch. Once you clean off the acid, the silver will be cloudy cream colour and the scratch will be copper colour.
Thinly plated items will typically turn brown from the copper or brass because there is not enough silver to make it turn red. The item may also react violently, give off black brown smoke and leave a yellow residue (sulfur) on your testing surface.

I always use nitric first to determine if a silver item is solid or plated.
If it's solid and I wish to determine a rough purity, I use Schwerter's solution.

It is economically feasible to recover silver and gold from silver plated and gold plated items, but it is not feasible to recover silver or gold from electroplated items. However, you may require hundreds of pounds of metal to make silver plated recovery economically feasible.

http://www.kmggold.com/faq-kmg-assaying-testing.cfm

Thanks,
Mike