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User @Poutnik has recently answered a question in which he/she quoted this statement from Wikipedia:

Almost all metals can form amalgams with mercury, the notable exceptions being iron, platinum, tungsten, and tantalum.

I am not sure about the validity of this statement as I found contradicting results regarding iron and platinum amalgams. There has been discussion around iron amalgams on internet giving inconclusive theories about why iron cannot form amalgam (See this reddit post for context) and on further research, I came to know that iron indeed form amalgam albeit unstable (See here). This has also been discussed in an another previous question. User @DrMoishePippik has pointed out that iron can form mercury-based alloys(amalgams?) at specific conditions. So, there is a contradiction regarding formation of iron amalgam.

Some searching also proved that platinum can also form amalgams:

Platinum Amalgam is obtained by trituration of platinum sponge with mercury in a warm mortar; it cannot be obtained by direct union of platinum foil and mercury.

The amalgam has a silvery appearance, and with 12 per cent, of platinum is soft and greasy to the touch, but higher percentages of platinum increase its stiffness. When heated strongly the mercury is volatilised and platinum remains as a grey residue.[...]

I searched the same site for tantalum alloys and gave me following information:

Sodium, potassium, mercury and silver do not alloy with tantalum even at high temperatures; attempts to prepare alloys with arsenic, antimony, lead, zinc and tellurium have also failed, but the formation of an alloy with silver, copper and tin for making a dental amalgam with mercury has recently been claimed.

No information about tungsten amalgam were given on that site. Other sources is giving me irrelevant information although the only other thing I found out is that since they doesn't form amalgams, they can be separated from a mixture of other metals using zinc amalgam.

So, the questions are:

  • Does tantalum and tungsten really not form amalgams?
  • If yes, what is the reason? Is it because of the same reason for iron not forming amalgam?
  • If no, is there any evidence/scientific papers to prove it?

I just saw a comment User @Mithoron has left in the question "Why does mercury not form amalgam with iron?"

Pt, W and Ta also resist dissolution with Hg

Is this statement true? Can anyone explain the statement?

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    $\begingroup$ Interesting question. The ASM Alloy Database does not even have an entry for Hg-Ta, strongly suggesting that it has not been studied much if at all. It does have Hg-Ti, and the phases there are quite different from, say, Ag-Hg which does suggest there may be difficulties forming an amalgam. $\endgroup$ – Jon Custer Jul 3 '19 at 12:56
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    $\begingroup$ It's also interesting that the metals concerned melt at rather high temperatures: 3290 K for Ta, 3695 K ​for W. Whatever is holding those metallic crystals together isn't letting much Hg sneak in. $\endgroup$ – DrMoishe Pippik Jul 3 '19 at 22:24

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