Color of yttrium ions??

[woelen]

I have some yttrium metal, which is supposed to be quite pure. I dissolved some of this metal in dilute hydrochloric acid of known high quality (no metallic impurities in the acid). The yttrium dissolves quickly with a lot of hydrogen formation, and the resulting solution is light yellow.

 

I suspected an impurity in the yttrium of iron. That would give a yellow color in the dilute acid, due to formation of yellow iron (III) / chloride complex. But on addition of some reagent for iron (III), yellow prussiate of potash, the liquid does not become blue. With iron (III) present, such that it colors the liquid visibly yellow, a thick dark blue precipitate would be formed. Instead, I obtain a light yellow/white precipitate. So, the impurity definitely is not iron.

 

Now I wonder, what is the color of yttrium ions? I cannot find a reliable source. The salt YCl3.6H2O is said to be white, but could the ions in a solution of HCl be yellow? I severely doubt that, I expected the solution to become colorless.

 

So, I still suspect an impurity, but then I ask, what is a common impurity for yttrium metal, which gives a yellow color on dissolving in acid?

[YT2095]

is This any good at all?:

 

Yttrium metal is available commercially so it is not normally necesary to make it in the laboratory. Yttrium is found in lathanoid minerals and the extraction of the yttrium and the lanthanoid metals from the ores is highly complex. Initially, the metals are extractedas salts from the ores by extraction with sulphuric acid (H2SO4), hydrochloric acid (HCl), and sodium hydroxide (NaOH). Modern purification techniques for these lanthanoid salt mixtures involve selective complexation techniques, solvent extractions, and ion exchange chromatography.

 

Pure yttrium is available through the reduction of YF3 with calcium metal.

 

2YF3 + 3Ca → 2Y + 3CaF2

 

taken from: http://www.webelements.com/webelements/elements/text/Y/key.html

 

is it possible that there maybe some 4F contamination?

[Tartaglia]

Some d0 complexes are actually coloured eg TiCl4(thf)2 is vividly yellow. Obviously it is not a d-d transition causing this, but there probably are other transtions as well invoving ligands.

 

Another problem with assigning colours to transition metals in these situations is that a minisule amount of any impurity with a metal ligand charge transfer band can give rise to a significant colour. Charge transfer bands have much higher extinction coefficients than plain d-d transitions which are actually quantum mechanically forbidden but become weakly allowed if symmetry is lowered

[Tetrahedrite]

I have some yttrium metal, which is supposed to be quite pure. I dissolved some of this metal in dilute hydrochloric acid of known high quality (no metallic impurities in the acid). The yttrium dissolves quickly with a lot of hydrogen formation, and the resulting solution is light yellow.

 

I suspected an impurity in the yttrium of iron. That would give a yellow color in the dilute acid, due to formation of yellow iron (III) / chloride complex. But on addition of some reagent for iron (III), yellow prussiate of potash, the liquid does not become blue. With iron (III) present, such that it colors the liquid visibly yellow, a thick dark blue precipitate would be formed. Instead, I obtain a light yellow/white precipitate. So, the impurity definitely is not iron.

 

Now I wonder, what is the color of yttrium ions? I cannot find a reliable source. The salt YCl3.6H2O is said to be white, but could the ions in a solution of HCl be yellow? I severely doubt that, I expected the solution to become colorless.

 

So, I still suspect an impurity, but then I ask, what is a common impurity for yttrium metal, which gives a yellow color on dissolving in acid?

 

I've done quite a bit of work with LREE compounds and even the analytical grade material (extremely expensive I might add) contains traces nearly all of the other REE's. I would suggest that finding which particular impurity is causing the yellow colour might be very hard as there are so many possibilities.

[woelen]

I in the meantime have looked further into this problem. I think that the impurity is (mainly) Pr. I also have some Pr metal and when this is dissolved in hydrochloric acid, then a deep yellow color is obtained. On dilution it becomes green and there is a definite color shift (probably due to ligand exchange, where chloride ligands are exchanged with water ligands). The same yellow color is obtained when I dissolve my yttrium. Also, the test with potassium hexacyanoferrate (II) gives a white/yellow precipitate with Pr(3+) also. So, the precipitate of Y(3+) could very well contain some co-precipitated Pr(3+) without a noticeable color change of the precipitate.