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...
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
Rainwater - 10-1-2025 at 15:34
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.
[Edited on 10-1-2025 by Rainwater]metalresearcher - 11-1-2025 at 03:22
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 $$$. RU_KLO - 11-1-2025 at 03:23
Understand, thanks.
Could one made of graphite work? Or graphite will be corroded too?
I don't mind carbon contamination.metalresearcher - 11-1-2025 at 03:30
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.unionised - 11-1-2025 at 04:16
Silver works if you aren't getting too hot.yobbo II - 22-4-2025 at 15:23
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 heatDraconicAcid - 22-4-2025 at 16:32
I got nickel crucibles off of AliExpress that worked fine for me.walruslover69 - 23-4-2025 at 12:22
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.......Sulaiman - 23-4-2025 at 18:59
I got nickel crucibles off of AliExpress that worked fine for me.
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?Keras - 23-4-2025 at 21:53
So, how re-usable are nickel crucibles
when used for reactions that require a nickel crucible?
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™'. Fleaker - 24-12-2025 at 19:42
I used to use graphite for molten KOH all the time. It does get corroded, but I was doing kilo scale fusions in an induction heater with a graphite
crucible.
I will say this much--contrary to what is reported--platinum is not a good material for fusions that see air. Any air and there is a problem.
Excusing gold, I think zirconium is best, followed by nickel, then nickel alloys like the inconels. Then plain iron.
I have done many a NaOH/NaNO3 in iron, at rather large scale where the iron products didn't matter. Safer at below 400 C. Higher than that, and Ni or
Zr.
