Separating Platinum from Gold During the Early Eighteenth Century

[dwtmint]

https://technology.matthey.com/content/journals/10.1595/003214089X3327380
Hi all, first post as I'm not much for intros.

I found this little gem in a platinum mine of information I just discovered today, the Johnson Matthey Technology Review.
The full 8 page PDF, attached and linked, has a great history of platinum in the Americas and how it was used to secretly debase gold sold to the Spanish.
Including several ways the Spanish solved the problem of separating it from gold.

 

[Yggdrasil]

View attachment 66947
https://technology.matthey.com/content/journals/10.1595/003214089X3327380
Hi all, first post as I'm not much for intros.

I found this little gem in a platinum mine of information I just discovered today, the Johnson Matthey Technology Review.
The full 8 page PDF, attached and linked, has a great history of platinum in the Americas and how it was used to secretly debase gold sold to the Spanish.
Including several ways the Spanish solved the problem of separating it from gold.

Welcome to us.

 

[Yggdrasil]

Anyone know what the units they are refering to here?
And what do they mean about decanting?
You can't decant solids?
Strange flowchart

Edit to add:
Found it, it is around 4.8g
And they decanted liquid Gold.

 

[Yggdrasil]

Don't Platinum and PGMs form proper alloys or are it possible to get Gold into a liquid state
at a temperature so low that the Pt is still a solid?

This challenges what I thought I knew about alloys.

 

[nickvc]

When you get platinum in a gold melt it tends to form a sponge like , brittle form , it’s easy to shatter the bar , especially if it’s from fillings from a jewellers bench , and it’s not easy to get an accurate assay .
Having read the PDF and the mention of skimming gold from the surface it makes sense , platinum really doesn’t like to alloy with gold.

 

[Yggdrasil]

When you get platinum in a gold melt it tends to form a sponge like , brittle form , it’s easy to shatter the bar , especially if it’s from fillings from a jewellers bench , and it’s not easy to get an accurate assay .
Having read the PDF and the mention of skimming gold from the surface it makes sense , platinum really doesn’t like to alloy with gold.

I saw that, but does that constitute the same as decanting?
Skimming it indicate that it behaves a bit like the Parkes process?

 

[nickvc]

I saw that, but does that constitute the same as decanting?
Skimming it indicate that it behaves a bit like the Parkes process?

I’m assuming that the platinum they had was in nugget or picker size pieces and as platinum has a higher density it sank to the bottom , this happens in gold platinum mixed fillings melts hence the trouble getting a decent assay.

 

[Lou]

Interestingly, pure gold and pure platinum alloy well and make a very durable alloy at about 900 parts platinum to 100 parts gold. This alloy is suitable for jewelry.

 

[4metals]

Interesting that Platinum was added to cut the gold because the Platinum was worthless and the gold was the big prize. Some human habits never change!