Electrochemistry metal nodules

[chemistrycoach]

hello and good day forumers, just wondering what this circular nodules are? its a 180 x magnification from a fire assay result to inquarting.. Pb Pt inquart. thank you very much for your sharing and have a GOOD DAY !

 

[Geo]

did you check to see if they are magnetic? they resemble iron balls ive seen after incinerating IC chips.

 

[chemistrycoach]

hi Geo, i tried to move it on a strong magnet , some of it goes with the magnet and some of it stays and did not move, does platinum group form nodules?

 

[Platdigger]

Just trying to understand. You say this is from fire assay, is this from multiple assays? Or perhaps from ground up cupels? Or?
Also, why did you inquart with pt?

 

[chemistrycoach]

hi Platdigger, we inquarted Pt from Pb ..the pt came from my jewelrer a scrap pt ring cut into small pieces,..we did this for some kind of educational experience and see through microscope what happens to a metal...we use new cupels.. digested the Pt Pb alloy in 50/50 hot nitric, Pb gone. what remains is very black Pt powder.. dried it and viewed it under 180 magnification.. and this is the result

 

[Geo]

i may be wrong about this, but there are better metals to have used besides lead. i would have thought about silver first and then maybe copper.

ok, you used lead/platinum alloy to teach inquarting. then you say that you use only new cupels. then you say that you used hot nitric acid to digest the alloy. when you inquart, you dilute the primary metal with a base metal that is reactive to nitric acid. you then digest the alloy in nitric which actually only digest the base metal taking the impurities in the primary metal with it. this process can result in the high purity of the primary metal.

from what you described, the Pt is the black powder you have.

you didnt cupel if you digested the alloy in hot nitric acid. when you cupel, you mix the primary metal with lead and then place the alloy in a cupel (a cup made of bone ash and cement). heat the cupel to 1000 degrees F. the lead will oxidize into lead oxide. the oxide is then converted by the MgO in the cupel back to lead metal and is drawn into the cupel. this leaves a bead of whatever metals are left.

 

[goldsilverpro]

In fire assaying, using nickel sulfide as a collector for Pt group seems to be the present state of the art. See Beamish.

 

[chemistrycoach]

yes sorry, what i mean is we used a brand new crucible to alloy the Pt and Pb then digest it in nitric acid to dissolve the pb and look at whats left of the pt in magnification. that was the purpose.. the pt was the black powder, it was the first time i will see platinum like charcoal in microscope, i was surprise then to see some round marble like metals, and asking what could it be.. do metals act this way ? are the round balls metals? thanks !

 

[Palladium]

Flux?

 

[nickvc]

It depends what the platinum jewellery was alloyed with, many modern alloys contain cobalt but old ones can have iridium as hardeners, the cobalt should have dissolved in nitric but I doubt iridium would so it's possible the balls could be undissolved metals from the alloy.

 

[goldsilverpro]

Since it's cheaper than iridium, ruthenium is often used. If I remember right, 95/5, Pt/Ru is quite popular.

 

[Geo]

depending on the crucible or melting dish you used, it could be silica.

 

[chemistrycoach]

thank you very much for your answer guys i think it is an alloy of other metals from the old platinum ring, im just amused to see such different colored nodules under magnification. again thank you !

 

[Platdigger]

If you weighed the ring before melting (smelting) to lead, how does the weight of the powder correspond?
Just curious.

 

[chemistrycoach]

oops sorry didn't measure it.. the jewelrer who sold me thinks is iridium, i was kinda curious why metals reacts this way? i mean its very beautiful just by looking at it.. like we are in another world... : )