# Metal won't dissolve in AR or anything else



## Rusty2751 (Jan 19, 2010)

G'day all,
Hope you had a great Xmas and New Year. I have been given a metal which has puzzled me.

It was a sheet of metal about 10cm x 75cm x 2-3mm thick. Bound with 5 turns of a pure silver wire.
It is malleable, flexible and looks and acts like lead sheet. Took the wire off and it dissolved it in nitric as usual (silver). The plate is another matter though. I treated it like lead and nothing dissolved, I thought that it might be Cadmium, tried HCL and sulphuric, but nothing. Then of course AR but still nothing happened. I don’t think that it is Pt or could it? How bizarre?
Any ideas would be appreciated.
Regards
Russ


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## Harold_V (Jan 19, 2010)

Platinum would be hard to miss, considering its specific gravity. It's roughly 10% heavier than gold. 

It doesn't dissolve readily, even in heated AR. 

What I'd suggest is a snippet off the corner, placed in a test tube with a few drops of AR, which is heated. If it is platinum, and starts to slowly dissolve, it will yield a yellow solution, similar, but not identical to gold. Allow the AR to work until it is somewhat exhausted, then test the resulting solution with stannous chloride. If it's platinum, you'll get a color reaction that is anywhere from a light brown to a dark coffee color, depending on the level of saturation. 

Harold


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## Rusty2751 (Jan 20, 2010)

Harold_V said:


> Platinum would be hard to miss, considering its specific gravity. It's roughly 10% heavier than gold.
> 
> It doesn't dissolve readily, even in heated AR.
> 
> ...



Thanks Harold, I'll give that a try on the weekend. Work has me tied up until then. I hope that it is high in Pt. I have about 300kg of the plates. I will let you know how it goes. If I can find the cord for my digital camera I will post some pics. I hate cleaning up for Christmas, I can never find anything...lol
Regards
Russ


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## Scott2357 (Jan 26, 2010)

I would be very interested in photos and test/process progress on this.


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## Rusty2751 (Jan 30, 2010)

I have boiled the metal in AR for 6 hours. There is definitely a reaction due to the amount of minute bubbles coming from the metal but the shape of the metal is the same. Slight positive stannous chloride test for Pt.
I have it in a fresh batch of boiling AR at the moment. I will let it go for another 6 hours and retest.

The metal in the photo was wrapped in 3 turns of fine Ag wire. Silvery grey in colour, Malleable. It looks like a battery cell plate to me, any ideas? Was there any such thing as a battery that had a Pt alloy structure? Military maybe…

regards
Russ


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## WIZZARD (Apr 19, 2010)

A reason some metals will not go into AR solution is due to the percentage of majority metals in an alloy, that resist certain acids, block the minority of those that will. Ir, Rh, Ru, Os as reduced metal will not go into solution with AR under normal conditions. If the majority metal of an alloy is Rh, Ir, Ru, Os it will not go into solution with AR. I noticed white powder like coating. If the oxides of metals form on the surface of the alloy, this too can restrict the alloyed metals from going into solution. If the Ag content is very high it could be AgCl and needs to be knocked off. A rotating digestion vessel of AR and grinding medium can work to knock off the resisting surface. If the metal is soft, the plate needs to be cut, spindled, mutated or rolled to micron size and allow the AR to reach the metal that will react with AR. Maybe fusion with Ag?, but that is another subject.


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## qst42know (Apr 19, 2010)

How does this metal react to a torch flame?

Platinized titanium is used in the plating industry. I wouldn't know how to test it but If you can confirm that this is platinized titanium your plates could be quite valuable as is.


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## Lino1406 (Apr 20, 2010)

Tantalum also won't dissolve


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## goldsilverpro (Apr 20, 2010)

All the platinized Ti or Ta plating anodes I've seen or used were made from expanded metal. As Lino suggested, it could be Ta sheet. It is heavy, with a SG of 16.65. I think it is totally impervious to AR below about 150F.


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## qst42know (Apr 21, 2010)

The Mesh may be the most common but apparently anodes are available in many configurations. If they are plating anodes (I don't know if they are)several exotic substrate metals could be used. 

http://www.optimumanodes.com/product_listing.html

The spider frame anodes for plating rims on this page are interesting. 8) 

http://www.optimumanodes.com/pure_plat.html


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## Rusty2751 (Apr 24, 2010)

Just a note to thank you for the replies to this problem. I have taken all of your theories and suggestions.
I am doing some more experiments on the plates but time has been a problem of late. Keep the replies coming.
Regards
Russ


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## JohnW (Apr 24, 2010)

Maybe it could be a Pt-Ir alloy?. I've never encountered this problem, but I read somewhere that a 20-40% Ir and 80-60 Pt alloy only dissolves very slowly in A.R.

If this is the case, the solution (a solution?) would be to melt (very difficult melt) and add lead 10-1 in weight, get an homogeneous melt, and then dissolve in A.R. again, before Pt and Ir separation.


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## jimdoc (Apr 24, 2010)

Russ said "It is malleable, flexible and looks and acts like lead sheet."
I don't think that would be the case if there was that much iridium in there.
Jim


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## qst42know (Apr 24, 2010)

It's not going to be a Pt alloy, clad or plated, or has some cemented to it perhaps. As a 300kg load would be well over 1/2 a billion dollars in solid Pt. Not even the military is that careless with money.


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