Fake Terbium?

Hello everybody, some time ago I purchased a 10g sample of "terbium" from eBay.
Now I dissolved in HCl, but it does not seems like Terbium at all. There is no trace of green fluorescence. At the beginning I thought it could have been quenched by water, but there is no way to see the green fluorescence even with the dry product.
Precipitating the tungstate gives a slightly pink fluorescence(?).
I don't know what it could be, maybe some cheaper rare earth?
It appears to not be fluorescent at all!

Now I precipitated with NaOH and kept the Hydroxide (white powder)
It could be possible that the fluorescence is somehow quenched by water? I think it should be visible in minimum amount.

here is a photo of it and a photo of a real terbium solution I got previously.

Quote: Originally posted by Maurice VD 37

Why don't you first weigh a bit and dissolve it in HCl, then evaporate the solution. Or precipitate the solution with NaOH, or with another reactant, then filtrate and weigh the precipitate ? Comparing the weights should give you an information.

Quote: Originally posted by Bedlasky

Iron contamination is usually big problem in fluorescent materials. Tb(III) is very slightly pink, so don't expect to observe some strong coloration of its compounds. If you add NaOH and persulfate in to your Tb(III) solution and heat it, you should obtain black precipitate of terbium(III, IV) oxide Tb4O7. Only preseodymium give you similarly looking product (but Pr(III) is green solution, so you cannot mistake it for Tb(III)).

Quote: Originally posted by ItalianChemist

With NaOH only the hydrated hydroxide seems to precipitate. [Edited on 11-12-2023 by ItalianChemist]

Quote: Originally posted by Bedlasky

Quote: Originally posted by ItalianChemist   With NaOH only the hydrated hydroxide seems to precipitate. [Edited on 11-12-2023 by ItalianChemist] You must add persulfate and heat it in the order to oxidize Tb(OH)3 to Tb4O7.

Ok so I think I can confirm this is Terbium
I got a small sample of the hydroxide and heated until it became red hot for a couple of minutes.
I obtained a black powder that should be Tb4O7, or a mixture of oxides.
The oxide obtained is pretty inert and doesn't seem to react with HCl.
None of the oxide shows any fluorescence

Quote: Originally posted by Bedlasky

You can try dissolve Tb(OH)3 in sulfuric acid and make some terbium sulfate. Lanthanide sulfates have very low solubility in boiling water, so you can precipitate most of terbium sulfate by heating the solution. In this way you should obtain pure terbium sulfate, iron contamination stay in the solution (just make sure you have small excess of H2SO4 in the solution to prevent precipitation of iron as basic sulfate).