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Author: Subject: How do noble metals rank and compare in terms of inertness for practical laboratory purposes?
VeritasC&E
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[*] posted on 29-3-2022 at 06:27
How do noble metals rank and compare in terms of inertness for practical laboratory purposes?


I can find some, sometimes somewhat contradicting, and never comprehensive, information for individual noble metals (as on the corresponding wikipedia articles), but I haven't found a full and comprehensive comparison and ranking amongst them all.

I'm wondering how noble metals (Copper, Silver, Gold, Palladium Group Metals, ...) rank versus each other in terms of their practical inertness (how versatile they are in being non-reactive to the greatest range of chemical conditions, in order of how likely these conditions are to be met in the course of normal operations in a chemical laboratory)?

[Edited on 29-3-2022 by VeritasC&E]
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[*] posted on 29-3-2022 at 06:43


In practical terms of inertness, I would rate them as follows:

Ni ≈ Cu < Ag << Au < Pt < Pt/Ir

In practice, I consider only Au and Pt (and even more so, alloys of Pt, containing a little Ir) as really useful for most chemistry. E.g. electrolysis with copper or silver anodes does not work, these metals simply are too reactive and are oxidized in electrolysis systems, when used as anode.

Vessels, in which reactions should be performed can sometimes be made of nickel, copper or silver, but only in quite specific cases (e.g. nickel for molten alkalies, copper for reactions with hydrazine at high pH).

A very special place has carbon (graphite, or even better, glassy carbon), which for some reactions can be extremely useful (electrolysis, but also as a crucible at high temperature in a non-oxidizing atmosphere).




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[*] posted on 29-3-2022 at 11:21


I don't regard Copper or silver as anytjhing like noble. Both dissolve rapidly in Nitric acid and have varied chemistry as metallic ions. Gold is a bit more difficult and dissolves readily in Aqua Regia. Palladium also dissolves readily in Aqua Regia. PLatinum is more resistant and only dissolves very slowly in Aqua Regia to make Chloroplatinic acid. As for the other platinumn group metals they are too expensive for me to have any direct experiance of, but I gather they are pretty unreactive. For me it's Cu>Ag>Pd>Au>Pt> the rest.



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[*] posted on 31-3-2022 at 20:36


One of my lab suppliers carries a range of Pd alloyed steel (5% and 10%)
They are of course extremely expensive and out of my price range. Some of these very expensive items make no sense to me. Why would someone need a 2000 Euros square shallow dish?
To serve to most expensive mac and cheese maybe.




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[*] posted on 31-3-2022 at 20:50


Quote: Originally posted by Herr Haber  
One of my lab suppliers carries a range of Pd alloyed steel (5% and 10%)
They are of course extremely expensive and out of my price range. Some of these very expensive items make no sense to me. Why would someone need a 2000 Euros square shallow dish?
To serve to most expensive mac and cheese maybe.

Pd alloyed steel seems like a weird idea to me. I wonder exactly what properties they are trying to impart that could not be achieved by other means.
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[*] posted on 31-3-2022 at 22:38


The nickel/copper alloy Monel is supposed to be pretty good for some things.

Very resistant to HF, but not to nitric acid.

It's sort of a mixed bag.





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[*] posted on 31-3-2022 at 23:51


Quote: Originally posted by j_sum1  

Pd alloyed steel seems like a weird idea to me.


Apparently it decreases susceptibility to hydrogen embrittlement.




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[*] posted on 14-4-2022 at 20:56


As I recall, some of the Nobel Metals resist even Aqua Regia.

Chemical resistance is case by case.

Not all of these metals are outrageously expensive.

Ruthenium for instance, was coasting along at $60/Oz. for several years.

I don't know what the price is now. I need to recheck it.

OK. I checked. Ruthenium is expensive now.

Expensive, for no particularly good reason.

The high price is probably due to speculation.

$620 US dollars per troy ounce.

[Edited on 15-4-2022 by zed]

[Edited on 15-4-2022 by zed]
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[*] posted on 16-7-2022 at 08:37


Thanks for your replies. This is useful information!
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[*] posted on 16-7-2022 at 10:04


A little more precisely, there so-called "Anodic index" which I find useful with respect to galvanic based synthesis (anodic corrosion) where I once dissolved in a microwave assisted reaction a rather noble tungsten filament with graphite rods cathode with a common household reagent https://www.sciencemadness.org/whisper/viewthread.php?tid=15... , to quote per Wikipedia at https://en.wikipedia.org/wiki/Galvanic_corrosion :

"This parameter is a measure of the electrochemical voltage that will be developed between the metal and gold. To find the relative voltage of a pair of metals it is only required to subtract their anodic indices"

More generally, per Wikipedia on reactivity series at https://en.wikipedia.org/wiki/Reactivity_series to quote:

"There is no unique and fully consistent way to define the reactivity series, but it is common to use the three types of reaction listed below...Reaction with water and acids...Comparison with standard electrode potentials..." where "The reactivity series is sometimes quoted in the strict reverse order of standard electrode potentials, which is also known as the "electrochemical series".

Also another alternative view at https://en.wikipedia.org/wiki/Reactivity_(chemistry) , to quote:

"Reactivity is a somewhat vague concept in chemistry. It appears to embody both thermodynamic factors and kinetic factors—i.e., whether or not a substance reacts, and how fast it reacts. Both factors are actually distinct, and both commonly depend on temperature. For example, it is commonly asserted that the reactivity of group one metals (Na, K, etc.) increases down the group in the periodic table, or that hydrogen's reactivity is evidenced by its reaction with oxygen. In fact, the rate of reaction of alkali metals (as evidenced by their reaction with water for example) is a function not only of position within the group but particle size."

I trust this helps on an apparently somewhat vague concept.

[Edited on 16-7-2022 by AJKOER]
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[*] posted on 17-7-2022 at 13:00


Quote: Originally posted by Fulmen  
Quote: Originally posted by j_sum1  

Pd alloyed steel seems like a weird idea to me.


Apparently it decreases susceptibility to hydrogen embrittlement.


I'm sure I read that somewhere in a discussion about power station generators but I haven't found a lot of info about it. I'd guess palladium's significant appetite for hydrogen absorption keeps the hydrogen away from the irons and carbons but if anybody's got any hard data I'd be interested to know.
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