Peter_leyw
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Chromium to Chromium (III) oxide
Hi,
First post in this forum, old timer (i still remember my chemistry basics lessons from 40+ years ago but i have no knowledge on this)
what would be the process to get Cr2O3 from Cr?
I'm looking for pieces (or chunks) of Cr2O3.
I've seen people using (NH4)2Cr2O7 to obtain Cr2O3 (in powder)
Thanks and glad to have found this forum.
[Edited on 21-1-2019 by Peter_leyw]
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oberkarteufel
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Cr2O3 starting from metallic Cr?
I think the best route would be reacting it first with HCl to transform chromium into CrCl3, then adding sodium carbonate (or hydroxide) solution to
precipitate Cr(OH)3. Then filtration and rinsing with distilled water. The last step is heating chromium (III) hydroxide, et voilà!
This way you will also get Cr2O3 powder however.
[Edited on 22-1-2019 by oberkarteufel]
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Peter_leyw
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Thank you!
i appreciate the informations even if the result is still powdered Cr2O3
Is there any way to get solid pieces of Cr2O3? (compressing the powder is not an option)
I saw someone mentioning growing crystals (no details)
Any informations on this process?
[Edited on 22-1-2019 by Peter_leyw]
[Edited on 22-1-2019 by Peter_leyw]
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Ubya
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water chemistry will give you just powderer oxide, you can't make an oxide crystal
so you need to press the powder but it's not an option for you, so just work with the powder
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feel free to correct my grammar, or any mistakes i make
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Peter_leyw
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The issue is that the painting and other fine arts ressources book i found (from the 1800's) mention that:
"If you can procure oxide (of chrome) do so in solid form, and not in powder (as pigment) and it cannot be compacted.
Only in solid form (so not wax either) but this form is very hard to find"
Could they have meant crystals?
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j_sum1
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Thread Pruned
23-1-2019 at 00:48 |
MrHomeScientist
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I've never heard of bulk solid chromium oxide as a chemical reagent. What use would a solid chunk have that the powder couldn't do?
Apparently there's a mineral form of Cr2O3, Eskolaite. That'd be about the closest you'd get.
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fusso
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Polishing?
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oberkarteufel
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I can't imagine anyone using solid/fused chunk of Cr2O3 for polishing. Actually, it's the powder that is mixed with molten wax/fats to get the "green
polishing paste". The same way, Fe2O3 is used to make "red polishing paste".
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Peter_leyw
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Quote: Originally posted by MrHomeScientist  | I've never heard of bulk solid chromium oxide as a chemical reagent. What use would a solid chunk have that the powder couldn't do?
Apparently there's a mineral form of Cr2O3, Eskolaite. That'd be about the closest you'd get. |
They mention and recommend the solid form (as pigment) on the canvas or specific surfaces for details (this is what the book mention)
Eskolaite is very expensive (and hard to find)
This is probably the source the book mention.
I found the "american elements" site list Chromium (III) oxide as available in powder and "crystals".
The "solid" form could mean that it was melted?
[Edited on 1-2-2019 by Peter_leyw]
[Edited on 1-2-2019 by Peter_leyw]
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