bereal511
Hazard to Others
Posts: 162
Registered: 9-8-2005
Location: Madison, WI
Member Is Offline
Mood: No Mood
|
|
Platinum Jewelry
I was wondering what the composition of platinum jewelry was and their substrates (if plated). I wanted to do some catalytic reactions with ammonia
to see if I could produce nitric acid as a science project, but I wasn't sure whether the composition would affect the reactions. Also, I was a bit
skeptical of this seller of platinum jewelry. I have no knowledge of platinum-plated jewelry prices, so I wasn't sure if these prices were too cheap
to be platinum. How would I check to see if it was platinum if I did buy it?
http://stores.ebay.com/MG-Jewelry_Platinum-Chain-Necklaces_W...
As an adolescent I aspired to lasting fame, I craved factual certainty, and I thirsted for a meaningful vision of human life -- so I became a
scientist. This is like becoming an archbishop so you can meet girls.
-- Matt Cartmill
|
|
|
BromicAcid
International Hazard
Posts: 3227
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
| Quote: | | This rhodium (platinum) chain necklace is simply amazing, because it will always stay shiny and will never lose its great platinum expensive look.
Rhodium is a raw form of platinum and it's one of the most expensive and precious metals on Earth. This chain necklace has several layers of heavy
rhodium plating over a heart of semiprecious metals, resulting in a much heavier thickness of rhodium (platinum). This increases durability and
wearability. |
Hummm... it looks like they consider rhodium the same as platinum, I wonder if there is even
any platinum in the necklace? I know platinum is found native mixed with other elements in its region of the periodic table and I'm not sure what the
native metal is called, but from that description the necklace is rhodium plated, it sounds somewhat thick but you should ask the seller.
[Edited on 12/15/2005 by BromicAcid]
|
|
|
s1
Harmless
Posts: 1
Registered: 15-12-2005
Location: New York
Member Is Offline
Mood: No Mood
|
|
Looking at the price of them I would say that they are rhodium plate sterling silver.
|
|
|
zoomer
Hazard to Self
Posts: 66
Registered: 22-3-2005
Location: Watching the sun set over the saguaros
Member Is Offline
Mood: Always Curious
|
|
Pure platinum is never used in commercial jewelry today, it is always alloyed 5%-15% with a variety of metals, especially iridium and palladium. It
is rarely if ever plated. However, most white gold (Au/Ni) jewelry is today electrolessly dip-plated with rhodium to increase its "whiteness." Any
commercial jeweler can dip-plate a ring for you in about 5 minutes. It is likely that the product described in your post is a less expensive metal
chain plated in this manner. Incidentally, this type of plating is only a few mils thick and typically lasts only a few years at best.
Unless you score big at a garage sale, platinum jewelry always costs more per gram than the raw materials. However, you can sometimes buy much
smaller amounts with jewelry, which can be easier on a limited budget.
A good discussion of platinum jewelry alloys and how they are marked is in this month's Ganoksin newsletter (an industry source).
http://www.ganoksin.com/borisat/nenam/platinum-alloys.htm
|
|
|
neutrino
International Hazard
Posts: 1583
Registered: 20-8-2004
Location: USA
Member Is Offline
Mood: oscillating
|
|
My advice is to go to a jeweler and get an old platinum wedding band. I got a 1-pennyweight one (~1.5g) for about the spot price ($35 back then). It
probably isn't totally pure, but a thin sheet (yes, I pounded a piece flat) glows in an atmosphere of acetone and air, so it should be pure enough for
any catalytic use. Remember that many other platinum group metals (Ir, Pd, Rh, etc.) are excellent catalysts, comparable to Pt itself.
|
|
|
garage chemist
chemical wizard
Posts: 1803
Registered: 16-8-2004
Location: Germany
Member Is Offline
Mood: No Mood
|
|
The ammonia---> NO2 reaction supposedly works with copper as catalyst too. Use a thin copper wire, preheat it strongly and put it into an
erlenmeyer with some concentrated ammonia solution in it. If it works the wire will continue to glow and white smoke (ammonium nitrate) and brown gas
(NO2) will become visible.
Maybe some of the nitrogen in the ammonia is lost as N2 this way, this might be the reason that industry doesn't use this process.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
