Dave Angel
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What to do with tiny bits of Palladium wire?
I was sorting through my lab equipment this weekend and I came across many wonderful things I'd forgotten I have, including 2 short lengths (ca. 50 mm
each) of fine (ca. 0.5 mm) Palladium wire. So, I'm looking for suggestions for interesting things to do with these...
Since electrochemistry is on my mind at the moment, my immediate thought was 'electrodes for something', but are there any particular physical /
chemical reasons that Platinum is usually preferred?
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liquidlightning
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Chlorate cell? Catalysis? And platinum or palladium?
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weiming1998
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Use the palladium wires as the cathode for electrolysis of dilute NaOH solution. It will absorb the hydrogen produced in the electrolysis. You can
then experiment with palladium that has hydrogen absorbed in it.
Edit: Organometallic chemistry with palladium, if you have the knowledge and equipment required, can possibly be interesting as well.
[Edited on 8-8-2012 by weiming1998]
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Dave Angel
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I've taken some better measurements now; the pieces are 0.5mm diameter and about 60, 80, and 50 mm long - it's not quite as ductile as I assumed Pd
wire would be so I now have 3 rather than 2 pieces...
Well, thanks for the ideas guys - I like the idea of some kind of catalysis so I'll be looking up some references at the library as a next step; I'll
post any interesting finds here. Or perhaps something as basic (whilst not simple in the home lab) as hydrogenation.
As an aside - a large, single crystal of palladium acetate would be quite a thing to grow - if one could afford enough metal or acetate to do it!
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Dave Angel
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Palladium (II) Chloride
So, in order to carry out the synthesis of acetonitrile that I have propsed here, I will be producing either PdCl2 or Pd(OAc)2 as the catalyst.
Standard PdCl2 production from the metal is reaction with aqua regia, or with hydrochloric acid in the presence of chlorine. I'd say the simple
solution would be to perform electrolysis with a Pd anode in hydrochloric acid. Boiling off the HCl would then precipitate the sparingly water soluble
PdCl2. Does this sound like a reasonable method?
[Edited on 17/8/2012 by Dave Angel]
[Edited on 17/8/2012 by Dave Angel]
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Fleaker
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Actually, PdCl2 is quite water soluble when prepared in that fashion.
Just dissolve in aqua regia, simmer to a sirup, add HCl and simmer down again, and repeat until no longer producing red fumes. You can then simmer
this down into a crust, and dissolve it in whatever solvent of suitable polarity and crystallize it out.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Fleaker
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Now that I think about it. You can trade me the wire for Pd salts and catalysts...
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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simba
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I made some PdCl2 these days by mixing palladium with hydrochloric acid and passing chlorine through it. It worked nicely, just like the aqua regia
method, but I didn't know any good way to recrystallize it, any tips on that?
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Dave Angel
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Thanks for the trade offer Fleaker but I think I'll hang onto them for now - I quite like the idea of trying methods to make my own
salts.
I reasoned, from the wiki on the chloride that states 'soluble in trace amounts', that once the HCl was gone from solution, it would precipitate from the, then, water
- but does the wiki entry mean trace amounts of water or trace amounts of the salt, as that changes the meaning a fair bit!
I've now found quite conflicting references online, some stating deliquescence, and others stating insolubility, so I'm far happier to go with your
personal experience with the salt - does it dissolve in water alone?
I find the idea of electrolysis of HCl(aq) quite elegant as it require only the one acid and electricity, rather than having to generate
chlorine or use the less readily available HNO3.
Do you see any disadvantages to the electrolytic method? (Besides my rapidly inflating electricity bills!)
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Fleaker
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No, electrolysis works just fine. Works for platinum too if the set up is right.
PdCl2 isn't terribly water soluble. It will slowly dissolve and form a brown-red residue over time.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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stoichiometric_steve
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Hello Fleaker, do you have any suggestions for the solvent to do the crystallization in?
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AdamAlden
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pute them in a vial and put it in drawer or on top of a book shelf.
I am a buttmeister
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Fleaker
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If you plan on using it over and over, I suggest to use it as its bromide, not the chloride. Far more easily recycled.
PdI2 < PdBr2 << PdCl2 insofar as solubility goes. Excess halide makes the [PdX6]2- (only in the cold will Pd(IV) last) or [PdX4]2- (usual).
Recrystallization of Palladium(II)bromide
Reagents used for 100 g PdBr2:
dissolution: 52.9 g sodium nitrite
3.9 g sodium bromide
400 ml water
crystallization: 80 ml sulfuric acid 1:1 (v/v); ca. 62% H2SO4
320 ml water
Solid PdBr2, together with the required amount of NaNO2 and NaBr are stirred in water at
room temperature. After about 1-2 hours all PdBr2 is dissolved, resulting in an intensely
orange colored solution, slightly turbid through some finely divided solid of varying greyshades.
Solids are removed quantitatively by filtration. The totally clear bromide/nitritesolution
of Pd is slowly added to the constantly stirred, slightly boiling H2SO4-solution. A
lot of brown fumes are escaping, and nearly black, fine crystals of pure PdBr2 precipitate.
The crystal-suspension is boiled under reflux until no more brown fumes are visible. After
cooling down to room temperature, the suspension is filtered. The now very pure PdBr2 is
washed free of acid with pure water and dried. Reduction on different ways delivers
usually a very pure metal, mostly 999.9%o Pd.
[Edited on 23-7-2016 by Fleaker]
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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