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Unknown Chromium Aluminium salt compound

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ThetaOmegaMu:
Hi I wonder if anyone can help me work out or identify a compound I've inadvertantly made.

I found a solution of 0.5M CoCl2 in a volumetric which had turned black.
I assumed that it had oxidised somewhat to CoO2 as there was no green colouring, and with conc ammonia I was getting a grey precipitate.

So I ended up try to extract the chromium by heating it up dissolving an excess of aluminium into it. Thinking that the chromium would precipitate out. However, that was not the case and it turned into a dark green solution.

I reduced the volume by 80% to a thick green residue and have been trying to coax crystals out of it.

What I've noticed from different tests is that it solidifies as an amorphous green solid with conc H2SO4 added.
HCl, HNO3, NH3, and NaOH does nothing and it stays as a thick green oil.

Any idea what ive made? I did wonder whether it was an intermetallic salt of some sort, but I'm an organic chemist really so not got the expertise.

Jorge Stolfi:

--- Quote from: ThetaOmegaMu on February 11, 2019, 08:30:27 AM ---I found a solution of 0.5M CoCl2 in a volumetric which had turned black.
I assumed that it had oxidised somewhat to CoO2
So I ended up try to extract the chromium

--- End quote ---

Co is cobalt; chromium is Cr.  Which did you mean?

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