a_bab - 28-12-2009 at 00:10
While trying to show the gorgeous color of indium in the flame to a friend of mine, I put a small piece of In metal on a Pt wire. The indium melted
quickly in the flame, but at red hot temperature it started to dissolve the Pt wire, turning into a slightly larger and much harder blob of metal that
advanced along the wire, consuming it.
This reaction seems to be of the "bimetalic fuse" kind (Pt/Al wire I guess) a member (Axt) documented.
Moral of the story: never use metals but salts for watching the flame colors on Pt wire.
Pics later.
12AX7 - 28-12-2009 at 00:26
Ah yes, all kinds of things attack platinum. It's really pretty awful as "inert" substrates go!
Let's see, In-Pt... there's a phase diagram, but it only goes up to 30%at! Only enough to show the first intermetallic, InPt3. Well, if Pt-Sn is
representative, there's probably a series of brittle intermetallics of descending melting point, all the way down to In, with the liquidus line being
roughly diagonal, so you might get 25% Pt in solution at somewhat more than 25% of the way between the melting points (1000K or so?).
It's probably not very exothermic as reactions go (not like nickel + aluminum), but it will certainly proceed.
Tim
[Edited on 12-28-2009 by 12AX7]