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Author: Subject: Divalent chromium
Bedlasky
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[*] posted on 6-2-2020 at 16:30
Divalent chromium


Hi.

I try few times prepare solution of Cr2+ from potassium dichromate, zinc and sulfuric acid. But I never obtain Cr2+ solution, only Cr3+. I read on the internet that this is standard method how to prepare Cr2+ solution. In chromometry is CrCl2 solution prepare in the same way - potassium dichromate + zinc + acid.

I know that Cr2+ salts are sensitive to air, but I have expirence with preparation solutions of V2+ and Ti3+ salts which are air-sensitive too and I never had a problem.
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DraconicAcid
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[*] posted on 6-2-2020 at 17:46


Perhaps hydrochloric acid is needed? Chloride ion does catalyze some reactions, so....



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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sciece nerd
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[*] posted on 6-2-2020 at 19:35


Do you have chromium metal?
There's a preparation on woelen's website.
https://woelen.homescience.net/science/chem/exps/chromium2/i...

[Edited on 7-2-2020 by sciece nerd]
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Fery
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[*] posted on 7-2-2020 at 03:04


Hi Bedlasky here a small gift for you. I did the synthesis a long long long ago (prep for IChO).
Everyone not understanding the language need OCR + translator.

Cr(II)_0.jpg - 171kB Cr(II)_1.jpg - 168kB




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Bedlasky
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[*] posted on 7-2-2020 at 04:42


DraconicAcid: I never try HCl, thanks for suggestion. Maybe there is some Cr(II)-Cl complex which help reduce Cr(III) to Cr(II).

Sciece nerd: Sadly I haven't any chromium.

Fery: Thank you very much! This is very useful article.
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sbreheny
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[*] posted on 7-2-2020 at 13:26


Fery: a bit off-topic but I like your signature line "If there is a heaven, it seems not to be materially based. Does chemistry exist there and if yes, how does it look like? Are there good souls well supplied with laboratory equipment, glass, chemicals and information?"

The traditional Christian concept of the afterlife is not a purely spiritual heaven but eventually, after bodily resurrection, a new creation where people will once again have both body and soul, but without the sickness and other limitations of this life, so yes, I bet there is chemistry there :)
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