Thread: PM Prices?
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Old 15 June 2018, 05:43 AM   #30
Zakalwe
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Join Date: Jun 2017
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Quote:
Originally Posted by BOA View Post
Actually, the atomic weight of gold is 196.97 while platinum is 195.08, which makes gold heavier. Platinum is #78 on the Periodic Table, and Gold is #79, so they are very close on a molecular level.
At the risk of turning this thread into a chemistry lesson...

Whilst you’re correct that Gold has a higher atomic weight, that means that the molar weight of gold is higher than the molar weight of platinum. Or to put it another way if you have an identical number of gold and platinum atoms, the gold will weigh more by a tiny fraction - circa 1%. However the poster you responded to said this:

Quote:
Originally Posted by GolfPunk View Post
Also platinum weighs more so there’s more grams of platinum required in the same case size.
And what he said is essentially correct. Per unit volume, platinum is significantly heavier, because it is denser than gold (21.45g/cm^3 vs 19.3g/cm^3). So if you take two identically sized watch cases, one made of pure platinum and the other made of pure gold, the platinum case will be circa 10% heavier. In reality platinum and gold watches are not pure elemental metal because these metals are too soft to be useful as watches and therefore because there is a lot more platinum in a 95% pt alloy watch case than there is gold in a 75% au alloy case, a platinum watch is even more than 10% heavier than the equivalent 18k gold watch.
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