RogueRose
International Hazard
Posts: 1585
Registered: 16-6-2014
Member Is Offline
|
|
Melted NaOH flowing/climbing up side of crucible & down outside
I needed to remove the enamel insulation from some wire so I melted some lye in a porcelain crucible using a blow torch. Once all the lye was melted
and I put the end of the wire in (it is 15 strands of 20 gauge) the melted lye, I noticed a pool of liquid form from underneath the crucible. It
seemed to come from nowhere.
It seemed to flow out faster when I touched the bottom of the crucible but it still came out when only 1/2 way into the lye. I could see what looked
like a thin layer of lye flowing up the outside of the crucible, looking like it was flowing in the opposite direction and it seemed to flow only in
the area where the flame was hitting the crucible (heating side perpendicular to side wall). The liquid that seemed to be traveling up looked like it
had soot in it, maybe from the enamel & the force of the flame - it kind of looked like a frothing overflowing beaker with VERY thin liquid but
flowing backwards.
The crucible was never more than 3/4 full and there was about 1/4" from the top, so there is no way it was overflowing.
Does anyone know what might cause this and why it happens?
|
|
|
Herr Haber
International Hazard
Posts: 1236
Registered: 29-1-2016
Member Is Offline
Mood: No Mood
|
|
Soot may be from the CO2 and well... NaOH
Other than that I dont know.
The spirit of adventure was upon me. Having nitric acid and copper, I had only to learn what the words 'act upon' meant. - Ira Remsen
|
|
|
rockyit98
Hazard to Others
Posts: 283
Registered: 12-4-2019
Location: The Known Universe
Member Is Offline
Mood: no mood is a good mood
|
|
use copper pot or magnesia pot to melt NaOH. porcelain can brake explosive like and spraying molten NaOH. i think its because about 10% of NaOH is
water if you add Ethylene glycol as a solvent to the melt it won't happen.
"A mind is a terrible thing to lose"-Meisner
|
|
|
WGTR
National Hazard
Posts: 971
Registered: 29-9-2013
Location: Online
Member Is Offline
Mood: Outline
|
|
What if you insert bare copper wire instead? Does it still do this?
I use a normal electric melting pot when doing this same task. When inserting the enameled wire it is normal for a lot of gas to rapidly come off of
the wire as the insulation is reacted away. Residue tends to float to the sides of the container, and a fine spray of
NaOH/Na2CO3 tends to build up into a solid ring around the top of the melting pot. The pot has a 2" flat ring around the top of
the container; this helps catch any spray/etc. that escapes the pot. I imagine that if I overheated the pot that this crust would liquify and escape
down the sides of the container.
I would suggest using a steel/stainless pot for this, not a ceramic one (and certainly not an aluminum one, ha ha!), and try not heating it as much,
especially at the very top.
|
|
|
wg48temp9
National Hazard
Posts: 761
Registered: 30-12-2018
Location: not so United Kingdom
Member Is Offline
|
|
Quote: Originally posted by rockyit98  | | use copper pot or magnesia pot to melt NaOH. porcelain can brake explosive like and spraying molten NaOH. i think its because about 10% of NaOH is
water if you add Ethylene glycol as a solvent to the melt it won't happen. |
Hot Ethylene glycol and NaOH slowly (unless powdered) dissolves glass, quartz and probably silicate ceramics like porcelain.
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
Old codger' lives matters, wear a mask and help save them.
Be aware of demagoguery, keep your frontal lobes fully engaged.
I don't know who invented mRNA vaccines but they should get a fancy medal and I hope they made a shed load of money from it.
|
|
|
12thealchemist
Hazard to Others
Posts: 181
Registered: 1-1-2014
Location: The Isle of Albion
Member Is Offline
Mood: Rare and Earthy
|
|
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 (can't say I've tried aluminium, can't say I want to  )
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
