[jdurg]

Just figured I'd share the news I've got here at the forums.  I will be getting a few new additions to my collection of the elements this coming week.  One of them is of an element that I do not own any samples of, and the other is an allotrope of an element that I did not posses and was admittedly too lazy to create.    The allotrope is the element tin in its gray form.  If one has the patience, they can take some regular tin metal and submit it to temperatures below 13 degrees Celcius for an extended period of time and it will slowly convert to the gray allotrope.  The problem with that is it takes a GREAT deal of time for this to be accomplished.  I didn't have the patience to do that so I just went ahead and purchased a sample of the gray allotrope to go along with my other purchase.

My other purchase is of an element which has eluded me for a while simply because I didn't really feel the need to go out and get it.  Now that I have all the stable elements and a couple non-stable elements, I thought that I should just go ahead and get some the attainable radioactive samples.  Therefore, I have gone and gotten myself a sample of promethium chloride.  Now unfortuneately the sample I will be getting was made from Promethium-147 which has a damned short half-life.  (2.17 years I think).  So in a short period of time a great portion of the PmCl2 will have decayed into NdCl2.  It's really too bad that I couldn't get some PmCl2 made out of Pm-145 as that stuff has a reasonable half-life.  (17 years).  So the promethium sample will probably be something that I have to re-purchase every few years.  

Now I just need to get myself a sample of Technetium metal.  As to how I'll go about doing that I have no idea.  I guess I'll need to find the right person at the right time.

[woelen]

How many (milli)grams of PmCl2 do you have? It would be nice to do chemistry experiments with that, although that of course requires some safety measures. I don;t know anything of the chemistry of Pm, but isn't it an interesting idea to make pure Pm metal, by dissolving some of this at a micro scale (in a few ml of water) and electrolysing this solution, such that a thin layer of Pm settles at a copper cathode or something like that? If you make a detailed picture of that, then your sample will "live" for longer by means of the picture.

And then the tin. I have purchased 60 grams of very pure tin from Emovendo. What about putting some of this in a freezer at -18 C? How long would it take at that temp before it turns into the other allotrope? An then, if I store it at room temp again, will it revert to normal tin, or does it stay like the special allotrope?

Btw, my red selenium is not very red anymore. The picture I have on my website certainly does not reflect the current situation anymore. Now it is more like a dark purple/grey powder. I stop making red Se, I have a picture on my website of this and I'm content with that. I of course keep the grey granules from Emovendo as my Se-sample, but the red stuff simply is too unstable. I do not want to replenish things every half a year.

[pantone159]

I think, once you turn the Sn gray, as long as you keep it below 13 C, it will stay that way indefinitely.
That is a more easily attainable temp than the one you need to make the white-to-gray transition happen quickly.

The last time I had some solid CO2, I hoped to make a dry ice/acetone bath, and try and summon the 'Tin Pest' by dumping the metal in that.  Unfortunately, I waited until the next morning, and the CO2 was all gone by then.

[Borek]

My freezer is -18 deg C. I don't have tin here, but it doesn't look very difficult to put some into the freezer for a few weeks - and it should be enough.

[P-man]

Cool. YOu can use any tin?

[jdurg]

The process of moving from one allotrope of tin to the other takes a good amount of time depending on the size and shape of your tin sample.  Solid lumps take a GREAT deal longer to convert due to the strong interatomic network that forms.  (A similar situation involving Osmium and why solid lumps don't oxidize but powders/sponges/small granules do).  Tin foil will convert quite quickly as will thinly hammered sheets.  Once it forms the gray allotrope it will remain that way pretty much indefinitely.  Gray tin is very "powdery" and just doesn't have enough "bonding" going on to convert back.  This is why items made of tin that have rotted continue to rot away and don't magically turn back even at warm temperatures.  If you have a freezer that can obtain temperatures below -13 Celcius then you can do it right in your own home.  The cost of the energy to do that may be a bit pricey though.  (That's why I went ahead and just bought some.  I figured it was much easier than trying to do it myself).  If you have access to liquid nitrogen, then you could dip your tin into the liquid N2 and the conversion takes place nearly instantly.

For the promethium, the PmCl2 is bound in a matrix with some activated ZnS.  A "paint", so to speak, on another object so my only way to truly "see" it is to see the glow caused by the beta decays striking the ZnS.  I would LOVE to have had enough to dissolve in some water and plate out onto some copper wire.  It's a shame that I don't have the time or resources to go and generate my own promethium.  Pm is readily formed by neutron absorption of Neodymium.  So if you have a good alpha source you could create a decent neutron gun, and with the use of a moderator, fire continuously at some neodymium metal and eventually turn some of it into promethium metal.  The trouble is containing all the radiation, avoiding oxidation of your neodymium (I.E. using an inert atmosphere), and then being able to check your sample afterwards.  (I guess if you had the reaction going for a year or so continuously you may actually be able to physically separate out the elemental Pm).

[jdurg]

With my selenium, it's kind of optically "strange".  When I look at it up close it appears pretty dark and almost a maroon color instead of red.  From a distance, however, it looks just as red as it ever did.  Very strange.

[Borek]

If you have a freezer that can obtain temperatures below -13 Celcius then you can do it right in your own home.  The cost of the energy to do that may be a bit pricey though.

Freezer I am referring to is just a bottom part of standard fridge standing in my kitchen, so no additional costs, just discussion with my wife to explain that this package WILL stay in the freezer. Although I am not sure it is set to -18 atm.