Sciencemadness Discussion Board

Element Collection Protection

careysub - 29-7-2016 at 11:31

I am looking for advice on what storage methods are needed for which element in an element collection.

We can assume that everything is in a nice clean dry case (I live in Southern California in an air conditioned house, so humidity is always low). And unless it is a massive chunk, it will be in a bottle at least.

There are the obvious ones that require ampoule or inert storage under argon or mineral oil (or both) - gases, the alkali metals, the more reactive alkaline earths (Ca, Sr, Ba), mercury, the halogens.

There are the obvious ones that don't: aluminum, gold, platinum, rhodium, zinc, tin, cadmium, nickel, chromium, silver (though sulfide tarnish protection will be used) since they are used for plating and protection. Copper also does not tarnish readily.

Arsenic and thallium will be ampouled because of toxicity concerns.

I know lead and bismuth tarnish readily.

But then there is a long list of metals whose tendency to oxidize I am less certain about. Until I get set-up for ampouling under dry argon myself I intend to use oxygen getter packets (micronized iron) if needed. For simplicity let us only concern ourselves with ones that *do* require some protection from oxidation/tarnish.

I have a list of "non-corroding" rare earths:
Dy, Er, Gd, Ho, Lu, Sc, Tb, Y, Yb
but I am uncertain how much I can trust this, since I find references to Yb for example being handled in air for "limited times".

Any others I should be concerned with protecting from tarnish?

BTW - I tried Googling SM for this, but all of the terms I could think of "element" "oxidation" "protection", etc. are heavily overloaded and bring up large numbers of posts that are unrelated to what I am looking for.

[Edited on 29-7-2016 by careysub]

NEMO-Chemistry - 29-7-2016 at 11:57

I havnt got a pic handy, but what about the little acrylic box's you can get in various sizes and shapes? They have a black base and normally used for keeping things like mineral samples in for display (i got mine from a shop selling minerals).

If you put you oxygen scavenger packets under a foam cushion or whatever then you could super glue the base to the top clear part to make it air tight.

At a push it might not need glueing! I am trying to search google for a pic of what i am on about as the camera is in the car!

NEMO-Chemistry - 29-7-2016 at 12:00

This is the kind of thing, you can get loads of sizes and shapes though.

http://www.ebay.co.uk/itm/4-X-EXTRA-LARGE-PERSPEX-DISPLAY-BO...

woelen - 29-7-2016 at 12:25

These boxes unfortunately are useless for protecting chemical elements from tarnishing or even completely corroding.

For some elements, the ONLY way of storage, which keeps the samples nice for years or decennia is ampouling in glass. All alkali metals, earth alkali metals, lanthanides, chlorine, bromine and iodine must be stored in this way.

Most transition metals also slowly tarnish, even copper, mercury, and silver. Use very well sealed glass bottles, with plastic liner and put some vaseline on the rim of the glass screw to assure a really airtight seal before closing the bottle.
Even aluminium, silicon, germanium and many other elements slowly tarnish over time (years, not months). Store these in sealed glass bottles with airtight seal as well.

ALL lanthanides are oxidized in air. Some of them are oxidized in hours and totally crumble in days (e.g. europium), others take months to become tarnished and years to crumble completely, but in the long run, ALL of them degrade on storage. So, lanthanide elements best are ampouled. At least store them in a very well sealed glass bottle. Fill the bottle with argon, propane gas or other non-reactive gas, before putting the metal sample in it.

The following elements are less critical on storage:
- sulphur
- selenium
- tellurium
- carbon
- silicon
- germanium
- gold
- platinum
- palladium
- iridium
- hafnium
- titanium
- niobium
- tantalum

Copper is tarnished easily, especially if you touch it. A touched piece of copper soon get dark spots on it and does not look attractive anymore. If you have copper, store it in a well-sealed glass bottle and do not open this bottle again.

careysub - 29-7-2016 at 13:35

Thanks, I suspected this was the case with the lanthanides.

I imagine in my dry climate tarnishing is slower than in the Netherlands.

Unprotected aluminum front surface mirrors (i.e. without an SiO overcoat), do not visibly tarnish over the course of decades here when used in laboratory conditions (reflectivity loss has to be measured with instruments, you can't see it).

How about zirconium?

[Edited on 29-7-2016 by careysub]

diddi - 29-7-2016 at 16:19

Zr is fine to store in open air.

I am using cheap apothecary jars and argon. so far I have not had too much problem with the REEs the more reactive ones have slight coating but nothing too bad. I am also looking at using heptane to cover them. uranium tarnished easily btw.

careysub - 29-7-2016 at 17:37

Quote: Originally posted by diddi  
Zr is fine to store in open air.

I am using cheap apothecary jars and argon. so far I have not had too much problem with the REEs the more reactive ones have slight coating but nothing too bad. I am also looking at using heptane to cover them. uranium tarnished easily btw.


Why heptane as opposed to some other hydrocarbon, like mineral oil (which I know must be de-oxygenated and dried).

NEMO-Chemistry - 29-7-2016 at 17:48

This shows I am no element collector!! To me a lump of copper in box in like that is fine, the darkening wouldnt be a problem and oxidation of aluminium etc would be noticed by me.

But then i guess its alot like stamp collecting, I have a old collection od stamps i inherited, they have been used (mostly) and have the post station frank marks on. A stamp collector i know has looked at my stamps and while some are from countries that no longer exist etc, he says its a poor worthless collection because the stamps are not pristine and unused.

I enjoy looking at them but it tells me i am no stamp collector and i dont get 'stamp collecting'. What you says about samples and being pristine makes sense, i guess i just didnt understand what is actually involved in element collecting.

Anyway sorry it was a waste of time, i hope you dont think i was taking the piss posting them as a solution! I have now had a look at some the pics on here of peoples collections, i had no idea what it was about until you see some of the collections! Fabulous looking and really neat idea, but its not for me, i am probably more a compound type collector :D.

diddi - 29-7-2016 at 23:22

I have a good supply of heptane. it is very clear compared to oils and much less viscous. that's the only reasons I use it.