# Laboratory Crucible PM? Rhodium?



## NobleMetalWorks (May 10, 2012)

Hello,

I just picked up a laboratory crucible for a grand total of $6.00, I thought it was worth the risk to see if it is made of platinum or rhodium. It has a stamped R with a circle around it. I couldn't find any information on it when I Googled it, and I do not have it in my hand yet, only the pictures that were posted on eBay. Yes, I bought it off eBay.

I know that there are lab crucibles made platinum, and sometimes they are alloyed with rhodium, and I have found a little information on rhodium crucibles, but I just simply don't know enough about them, to know if any are identified by a circle R hallmark. Anyone have any idea if I just bought a knick kanck or if the crucible is made of precious metal?

Dimensions are 42mm x 40mm height x width, it's small like a precious metal crucible.

Pictures:













I have bought a platinum crucible before, it was banged up pretty good but still was nice and shiny. This one looks well used, you can even see what looks like might be small fractures in the bottom. It is also not banged up, dented or miss shaped. I have to believe because it looks like it's well worn, that it is. If it were platinum I might expect it to be banged up as platinum is soft. If it was rhodium it probably wouldn't get banged up as it's much harder, but I would expect it to have a nice shiny finish. Could repeatedly heating and cooling cause the type of coloration in the pictures if it were rhodium?

Thanks for any advice or information

Scott


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## etack (May 10, 2012)

You could test with heat like Lou says to do with most things thought to be PMG. heat till red and see if it oxidizes.

Eric


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## NobleMetalWorks (May 10, 2012)

Exactly what I was planning on doing when I receive it, it hasn't even been shipped yet, I just bought it on eBay of all places.

I do know that Rhodium, at around 1100 degrees C, or 2012 degrees F, will become coated with a thin film of oxide. I am kind of hoping that is what the patina is that you can see in the pictures. I just don't know enough about laboratory crucibles. I really hope the circle R is a mark that can identify what type of metal it's made of.


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## NobleMetalWorks (May 10, 2012)

Also, here is a site that has really good information on lab crucibles. This page has to do specifically with Rhodium Crucibles

http://www.americanelements.com/rhcr.html


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## qst42know (May 10, 2012)

Many things it might be.

http://www.americanelements.com/nicr.html


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## Lou (May 10, 2012)

Probably just a nickel crucible. If it crushes easy and doesn't tarnish with heat, it's platinum. If you can add sulfuric acid and boil it and it doesn't go green or eat the surface, it's platinum (otherwise it would be zirconium, iron, or nickel).



FYI, rhodium will always stay shiny and it doesn't patina. That oxide layer is unstable at lower temperatures....I've heated much rhodium.


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## etack (May 10, 2012)

this is also informative http://www.rochoet.com/product_categories/crucibles/guidelines_for_crucibles.html

It has a section on ruining Pt curibles. :lol: 

Eric


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## NobleMetalWorks (May 10, 2012)

Thanks Lou,

I'm thinking it's probably nickel also. Worth the $6.00 to learn in any case. I'll post here when I receive it and test for PM.

Scott


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## Lou (May 10, 2012)

Fast way to ruin a Pt crucible is to use any sulfur or other chalcogenide in it! Instant fatality.


Good job in that other thread--it should go in the Hall of Fame of scammer butt whoopin'.


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## NobleMetalWorks (May 10, 2012)

Lou,

You know sometimes I re-read what I write and edit for spelling, I need to learn to check my spelling before I hit the submit. I also read what I write and sometimes think of what a jerk I sound like, I hope I don't come off that way. I feel real strongly about international scammers, I have had to deal with a lot of them. Thanks for the compliment. I hope someone calls me out if I am being too jerky though.

Scott


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## nickvc (May 11, 2012)

Scott you won't get any complaints off me.
Your doing what most active and or senior members do which is watching the backs of those less acquainted with the world of con artistes which are all too common in this particular field 8)


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