woelen
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Completely volatile metal compound, even from aqueous solution!
Last weekend, I transferred a little ruthenium oxide (black RuO2) from my stock bottle to a small vial, and the plastic spatula, used for that, still
had some of the black powder adhering to it. I thought it would be a pity to spoil that little amount of powder, so I did 5 ml of bleach in a small
glass beaker (25 ml) and rinsed the spatula with that bleach. The powder came into the bleach and slowly dissolved. It gives an olive green solution
(due to formation of perruthenate, RuO4(-)), but soon, the solution turned more yellow and somewhat lighter. There also was production of some gas
(most likely oxygen). I did not apply any heat. Room tempoerature is between 10 and 15 C.
I put the beaker on my workbench, left it open, uncovered. Yesterday (4 days later), I checked the beaker. It still had more than 3 ml of liquid in
it, but the liquid was perfectly colorless. Around the beaker, the workbench was stained with a grey color. The labels on two nearby bottles were
grey, where they were facing towards the beaker, and still white at the other side, facing away from the beaker. The beaker itself also was somewhat
gray on the outside. When I took away the beaker and the two other bottles, I saw that where these items were on the workbench, it still has the right
wood-color, so now I have a gray spot on the workbench with three circular areas in it which are not stained. On some nearby glass items I saw grey
fingerprints and grey streaks at places where glue remains of once removed labels were on the glass items. Apparently the stain is formed on reducing
surfaces (grease from skin and organic remains).
To the colorless liquid in the beaker, I added some 37% HCl. This leads to formation of a little gas (chlorine) and the liquid turns bright yellow and
becomes turbid with a compact white precipitate. On addition of a little water, the precipitate dissolves and a clear bright yellow liquid is
obtained. These observations can perfectly be explained. The liquid is based on concentrated bleach (12.5%). With the concentrated HCl added, some
NaCl precipitates and Cl2 is produced, but also ClO2 (the bleach is somewhat older and hence contains some chlorate as well). The ClO2 gives the deep
yellow color. On adding a little water the NaCl dissolves and the dissolved ClO2 gives the liquid its bright yellow color. So, the liquid in the
beaker must have been simply some old mostly decomposed bleach.
The only explanation I have for these observations is that all Ru has escaped the aqueous solution and that it is much more volatile than the water in
which it was dissolved. Most likely this compound must have been RuO4. It is remarkable, that this compound even survives the alkaline bleach. It
hence is not an acidic oxide, but an indifferent one (it also is not amphoteric, nor basic).
This also must be read as a warning. Ru-compounds apparently very easily escape from solutions when they are strongly oxidizing. RuO4-vapor is
dangerous (like OsO4, albeit less severe). I only had very small amounts (most likely just a mg or so, it really was just a thin layer of powder
around the spatula), but even this very small amount has enormous staining power. An area of 30x30 cm2 is stained around the beaker.
[Edited on 6-11-20 by woelen]
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DraconicAcid
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I despise osmium so much that I can't see myself wanting to ever work with ruthenium (even ignoring the fact that my ex-wife's family came from
literal Ruthenia). But thanks for the warning.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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chornedsnorkack
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Boiling point is reported as 130 Celsius for OsO4, but just 40 Celsius for RuO4.
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Herr Haber
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Very interesting.
Specially after watching Tdep's video yesterday
https://youtu.be/KQ4FwxgsGw4
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
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MidLifeChemist
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This is very interesting, thank you. Is this the first time you've oxidized Ruthenium dioxide?
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Bedlasky
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Woelen: Yes, I read it few days ago here.
RuO4 is formed even in alkaline conditions. But it isn't stable, because it reacts with OH- to form perrhutenate. Perruthenate is also unstable, but
much more stable than RuO4. Perruthenate also reacts with OH- to form ruthenate which is perfectly stable in alkaline solution. But this reaction take
a longer time. So maybe if you heat the solution, RuO4 after its forming quickly reacts with OH- to form perrhutenate (like in experiment on your
website). But at room temperature is reaction between RuO4 and OH- slower, so RuO4 escapes from solution. I'll check this theory - add small amount of
RuO2 in to bleach or alkaline persulfate, cover the top of the test tube with paper tissue soaked in sodium metabisulfate solution, heat it and see if
on paper tissue will be some RuO2 stains.
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Cryolite.
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I've dissolved ruthenium sponge before in order to convert it to RuO2 (and subsequently to "ruthenium chloride") and I've found that making the bleach
solution alkaline to ~ 2-3 M NaOH completely eliminates the production of the tetroxide. I roughly followed the following paper for a procedure: the
absence of ruthenium mirror formation with the use of alkali helped tremendously with my peace of mind! https://sci-hub.se/https://pubs.acs.org/doi/pdfplus/10.1021/...
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beta4
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Is ruthenium chloride safe, or does it decompose to the tetroxide somehow?
I'd like to get some to make Tris(2,2'-bipyridine)ruthenium(II)chloride, but first I'll have to make the bipyridine which isn't going to be easy.
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Bedlasky
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Ruthenium chlorides don't decompose in to RuO4. For formation of RuO4 you need very strong oxidizing agents.
[Edited on 7-11-2020 by Bedlasky]
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Pok
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RuO4 is quite interesting. I made a few grams of it with a quite simple procedure I developed by myself. Here you can see the first results. The video
shows the synthesis and destruction of about 7 grams of RuO4: https://www.youtube.com/watch?v=EyUlDvJ3Yho
[Edited on 7-11-2020 by Pok]
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draculic acid69
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Isn't bleach and osmium/ruthenium a way to make deadly deadly tetroxides?
Isn't this the reason why ru/Os metal used in jewellery dangerous?
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Metallophile
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I'm confused by this video. Which part is the RuO4? Wouldn't heating it over a flame make it boil like crazy? The B.P. is reported up-thread to be
40C.
[Edited on 11/9/2020 by Metallophile]
[Edited on 11/9/2020 by Metallophile]
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woelen
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Quote: Originally posted by draculic acid69  | Isn't bleach and osmium/ruthenium a way to make deadly deadly tetroxides?
Isn't this the reason why ru/Os metal used in jewellery dangerous? |
If you read the above, then you could have drawn that conclusion yourself. Bleach is capable of oxidizing Ru-compounds to RuO4, albeit slowly.
Probably a similar reaction occurs for Os-compounds, but I do not have personal experience with that.
RuO4 is dangerous stuff, if handled carelessly, but isn't that the same with a sharp knife, or even more so, a chainsaw?
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Bedlasky
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Bleach contain hydroxide, so osmium should be oxidized in to osmate and perosmate, because OsO4 reacts with hydroxides to form perosmate.
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Tsjerk
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Bleach doesn't have to contain (much) hydroxide.
Edit: bleach is even pretty stable at around pH 7.
[Edited on 9-11-2020 by Tsjerk]
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Bedlasky
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Still it is alkaline. Even if hydroxide content is low. If you dissolve little bit of osmium in a test tube with bleach, it doesn't change pH too much
- so perosmate will form.
[Edited on 9-11-2020 by Bedlasky]
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Pok
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The orange lump. I will load up the whole video with explanations in some weeks or so.
Well, that's simply wrong. The real boiling point of RuO4 is 129.6 °C.
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chornedsnorkack
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Ah, very interesting. A case of gross error in Wikipedia.
A source for pKa:
13653075 - Pure and Applied Chemistry] Dissociation contants of inorganic acids and bases in aqueous solution.pdf
from
www.degruyter.com%2f Download Pdf%2f Journals%2pac%2F20%2F2%2f Article-p133.pdf
but could not make the link functional
gives the pKa for both as near 12.
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