RU_KLO
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Crucible for NaOH fusion
I need to perform fusion with NaOH + NaNO3 + Na2CO3.
the book asks for nickel crucible.
I read the wiki crucible:
https://www.sciencemadness.org/smwiki/index.php/Crucible
Getting a Nickel or magnesium oxide is difficult for me.
In another posts:
"The one time I melted NaOH in a porcelain crucible, I ended up destroying it by simply dissolving/weakening the ceramic to the point of failure. I've
never had this problem with metal crucibles "
http://www.sciencemadness.org/talk/viewthread.php?tid=154253...
"But as mackolol said plain ceramic should be ok, I also did a lot with molten NaOH and KOH in them"
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
the procedure ask for a NaOH "bed" in the bottom of the crucible, the sample (fine ground) above this bed and in the middle, on top a layer of NaNO3 +
Na2CO3.
heat (slowly) till everything dissolves. (no more that 15 sec in a nickel crucible)
Can this be "substituted" with a common porcelain crucible (which I can get)
I understand that alkaly (molten even more) attacks porcelain, but maybe not too hot (only until melting) and 10s there is no such attack or is minor.
(more important, not contaminating the sample - or trace contamination that will not invalidate the analysys)
Does anyone has experience with this?
Thanks
Go SAFE, because stupidity and bad Luck exist.
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Rainwater
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So any type of ceramic material (ether Al or Si based) will dissolve is this mixture.
So will aluminum containers
You need nickel or platinum to prevent contamination of your product.
Cheap stainless, cast iron, etc will intorduce iron contamination turning your molten salt a black, then brown, then red
Good stainless will introduce crome turning first a light blue then a darker blue.
If this will effect your chemistry is unknown to me
I use these little cups with molten NaOH.
https://www.amazon.com/gp/aw/d/B06XZB1ZG2
[Edited on 10-1-2025 by Rainwater]
"You can't do that" - challenge accepted
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metalresearcher
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Amazon does sell Ni crucibles.
https://www.amazon.com/s?k=nickel+crucible&crid=2HCLRQQR...
Ni is rather restistant to molten lye. NaOH with the other two salts dissolved in it is still very aggressive to most other materials.
Pt is the best but very $$$.
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RU_KLO
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Understand, thanks.
Could one made of graphite work? Or graphite will be corroded too?
I don't mind carbon contamination.
Go SAFE, because stupidity and bad Luck exist.
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metalresearcher
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Quote: Originally posted by RU_KLO  | Understand, thanks.
Could one made of graphite work? Or graphite will be corroded too?
I don't mind carbon contamination. |
Graphite will be corroded I think, but it is an assumption. I have never tried.
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unionised
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Silver works if you aren't getting too hot.
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yobbo II
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Can you use a 'skull' of the mixture?
Use large dish to hold the stuff and heat from the top.
The container does not see much heat
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DraconicAcid
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I got nickel crucibles off of AliExpress that worked fine for me.
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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walruslover69
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I have used both a graphite crucible and a stainless steel cocktail tumbler to heat NaOH + cyanuric acid+ sodium carbonate up to 800C for cyanide
synthesis and it worked well. Both crucibles looked worse afterwards. You could maybe run the reaction twice before the crucibles failed, but they
didn't seem to significantly contaminate the reaction. A bunch of black graphite dust carried through, but nothing that a quick filtration through a
sand column can't fix!
depending on your budget a nickel crucible would be really nice to have.......
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Sulaiman
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Although not expensive in general
chemistry equipment terms,
they are not in my 'disposable' price range
(equiv.USD13or18 for 30or50ml with lid)
So, how re-usable are nickel crucibles
when used for reactions that require a nickel crucible?
CAUTION : Hobby Chemist, not Professional or even Amateur
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Keras
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I have a nickel (or is it stainless steel? I think it’s nickel) crucible, and there’s no problem reusing it over and over. I used it for several
high temperature fusions, such as making p-cresol from sodium p-toluenesulphonate or recently indigo from phenylglycine o-carboxylic acid.
What I usually do is scrape it with a rag full of some cleaning/polishing paste, such as 'The Pink Stuff™'.
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