What do I have here?

[goldenchild]

Here is whats left over after processing some gold filled watch bezels. They were white gold. When removing the base metals from the bezels using nitric I thought these foils might be some kind of aluminum coating hence why they werent attacked. However, they even survived the AR digestion. They are very shiney and appear to be silver but I know that just cant be. I tried incinerating them afterwards thinking it may be something non metalic but they became red hot.

 

[Harold_V]

It has been common practice to plate with rhodium, not only on sterling, but white gold. Not suggesting that's what you have, but it's a possibility.

Harold

 

[lazersteve]

I'm going to guess Rhodium also, put a small sample in concentrated sulfuric acid and heat for 10 minutes once white fumes are produced. Be very careful with this hot concentrated acid as it is very dangerous.

Not all of the sample will dissolve, but If you end up with a red-brown solution that test positive to stannous chloride, you have Rh.

Here's what the Rhodium Sulfate solution looks like after Rh digestion in hot H2SO4 looks like:

and here's the process for testing Rh solutions with stannous chloride:

Stannous Test of Rh in Solution

Steve

 

[dtectr]

i was going to guess rhodium - when i was working in the industry, the guy i worked for Rh plated everything silver-colored, sterling & white gold.
a way to tell the difference with solid metal is to moisten a piece of white tissue paper, the kind you pack gifts in. Place it on the metal in question.
Rh is a "black" metal, whereas silver is a "white" metal, as seen thru the tissue. worked every time.

 

[goldsilverpro]

i was going to guess rhodium - when i was working in the industry, the guy i worked for Rh plated everything silver-colored, sterling & white gold.
a way to tell the difference with solid metal is to moisten a piece of white tissue paper, the kind you pack gifts in. Place it on the metal in question.
Rh is a "black" metal, whereas silver is a "white" metal, as seen thru the tissue. worked every time.

It looks and sounds like Rh to me, also.

That's the first time I've heard of anyone else doing that. I commonly used the wet tissue (we used white Kleenex or lab tissue) method, 40 years ago, mainly to distinguish between different colors of decorative gold plating of different karats on test panels. The tissue was placed over the panel and a little water from a squirt bottle was added. To prevent wrinkles, I held the tissue slightly taunt while applying the water - if you hold it too taunt, it will tear when it gets wet. The wet tissue becomes almost totally transparent and removes all the glare from the reflected light. All you see is the true color. Usually this was done with 2 or more samples, side-by-side, so you got a comparison. Like dtectr said, it works like a charm. Although the color of 2 different shiny metals look near the same in the light, the tissue method will dramatically show subtle color differences.

 

[samuel-a]

Mario

i had the same thing when processing white gold from gold filled watch band caps.
i'm 99.9% sure it's Rh....

 

[goldenchild]

I will give these techniques a try if I ever get the time. There doesn't seem to be enough hours in the day. And that pesky day job... :lol:

Gold is at 1277!