Sciencemadness Discussion Board

Thermal Tolerance of this crucible

vibbzlab - 12-11-2019 at 07:08

Hello friends
I just bought a porcelain crucible
I don't know how much temperature it can withstand.
I knew that silica crucible is way better,but the cost made me buy this one.
If someone could help me please tell

IMG_20191112_203513.jpg - 1.1MB

Sulaiman - 12-11-2019 at 07:28

Most seem to be rated just over 1000oC
e.g. 1050oC

vibbzlab - 12-11-2019 at 07:49

I was planning to make phthtalic anhydride from Phthalic acid by heating it

Ubya - 12-11-2019 at 08:16

Quote: Originally posted by vibbzlab  
I was planning to make phthtalic anhydride from Phthalic acid by heating it



.....
why did you even ask then, the dehydration reaction of phthalic acid to the anhydride happens at 180-200°C, how could you think that a porcelain crucible couldn't withstand it?
nurdrage and many other amateur chemists did this reaction in a plain normal beaker without any problems, why the hassle of using a crucible?

vibbzlab - 12-11-2019 at 08:21

I bought crucible for thermite reaction

Ubya - 12-11-2019 at 08:49

Quote: Originally posted by vibbzlab  
I bought crucible for thermite reaction


Depending on the termite reaction it could survive or not.
Iron oxide+aluminum, probably it won't survive
Copper oxide+aluminum, it won't survive for sure (boom)

For termite reaction you are better using cheap flower pots, if you check a few videos on YouTube you'll know why.

vibbzlab - 12-11-2019 at 08:52

Will silica crucibles survive that?

SWIM - 12-11-2019 at 10:10

Graphite will.
Not sure about silica but don't think so.

Silicon dioxide supposedly can be used in a thermite reaction with aluminum and sulfur to make silicon.

Even if the crucible stayed intact I'd be worried about serious pitting, which wouldn't be easy to rectify and might make the crucible a real drag to use.

There's a lot to be said for using Terra Cotta pots as Ubya said above.
They're cheap, and if one does fail, who cares? It's not like you just ruined an expensive crucible made of unobtanium.

A lot of the thermite reactions reported here have been done in steel containers. Not Al/FeO, obviously, but lower temperature reactions for reducing various alkalais to metals.

vibbzlab - 12-11-2019 at 17:38

I will get terracotta ones then

Sulaiman - 12-11-2019 at 17:51

Small note :
if you look at your porcelain crucible and lid you will notice un-glazed areas, typically around the rims.
This is not a manufacturing defect, it is where water vapour is allowed to escape.

So before blasting the crucible with heat,
slowly increase the heat to well above 100oC to eliminate water that is trapped in the bulk of the material,
otherwise there is a significant possibility of cracking due to the internal pressure of superheated steam.

vibbzlab - 12-11-2019 at 18:02

Ohh great. I just noticed that. Thanks for that

wg48temp9 - 12-11-2019 at 20:45

Quote: Originally posted by Sulaiman  
Small note :
if you look at your porcelain crucible and lid you will notice un-glazed areas, typically around the rims.
This is not a manufacturing defect, it is where water vapour is allowed to escape.

So before blasting the crucible with heat,
slowly increase the heat to well above 100oC to eliminate water that is trapped in the bulk of the material,
otherwise there is a significant possibility of cracking due to the internal pressure of superheated steam.


The unglazed area is usually the area were the ceramic item seats on the kiln shelve and if the item is fired properly the body should not be porous but perhaps cheap items are.

I have a ceramic mug that can not be put in a MO because if you do the ceramic can gets very hot particularly the handle Ouch!!!. All my other ceramic mugs do not absorb microwaves even though they have an unglazed rim on the bottom because water can not get in to them as they are not porous.