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Author: Subject: Palladium Chloride decomposition in air?
Sidmadra
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[*] posted on 17-8-2018 at 09:41
Palladium Chloride decomposition in air?


I've got a couple dozen grams of PdCl2 that I made about 2 years ago, and I've noticed that not only has it absorbed moisture in the container, but after drying again in the oven, there is a noticable amount of black particulate, suggesting to me that some of the PdCl2 has perhaps decomposed to metallic Pd. During drying, there was trace chunky palladium left on the spoon I used to transfer it for about an hour. When I checked the spoon again, all of the PdCl2 on the spoon had turned from it's normal reddish color to a black color. I am unsure if this is just from moisture absorption or some sort of decomposition.


I recall the last time I used this PdCl2, the reaction I used it in had lower than expected yields. The yields should have been quantitative but were much less so, suggesting not all of the Palladium was active. This would be explained if there was some sort of partial decomposition into metallic palladium that took place.



Does anyone know what is happening here? Is it actually decomposing somehow, or is this misleading? I could reactivate it by boiling again Aqua Regia / HCl, but if there is decomposition happening I'd like to come to an understanding of how.



[Edited on 17-8-2018 by Sidmadra]
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CouchHatter
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[*] posted on 17-8-2018 at 12:39


I got a couple grams a few years ago in a shielded, sealed bag that I never opened. I looked at it a few months ago and noticed the same discoloration you described. Its stored in the dark, but for about 2 months it was subjected to an uninsulated storage space. Probably >120°F at times.
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wg48
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[*] posted on 17-8-2018 at 13:09


The Pd will plate out on most metal spoons if the chloride is damp as the metal of spoon will displace the Pd. Use a plastic spoon.



Borosilicate glass:
Good temperature resistance and good thermal shock resistance but finite.
For normal, standard service typically 200-230°C, for short-term (minutes) service max 400°C
Maximum thermal shock resistance is 160°C
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Sidmadra
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[*] posted on 17-8-2018 at 13:50


Metal spoon aside, would PdCl2 undergo decomposition to palladium metal when exposed to air? I'm most likely going to submit it again to an aqua regia treatment before using it again anyways, but nevertheless.
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