stephill92
Harmless
Posts: 23
Registered: 19-3-2019
Member Is Offline
|
|
Issue with magnetic stirrer
Don't know if this is an issue with the actual hot plate or if I'm using the wrong stir bars but I bought this same model of hot plate/magnetic stirrer about a year ago and I've always had an issue with the stir bars spinning out but mostly it was
manageable. Mostly it was an issue with erelnmeyers but today was the last straw. I was trying to make sodium using the menthol catalyzed sodium
hydroxide magnesium method and it will not even go the slowest possible speed without spinning out and jumping up on the side of the flask. Is this a
common issue with magnetic stirrers and is there a way to fix it? Or did I just buy a piece of junk?
|
|
|
j_sum1
Administrator
Posts: 6218
Registered: 4-10-2014
Location: Unmoved
Member Is Offline
Mood: Organised
|
|
A lot comes down to the stir bar you use.
Experiment with different sizes, banded and unbanded and oval bars. They do not behave the same way at different speeds and with different
viscosities.
(I lost my small oval one the other day which was perfect with my 500mL RBF slightly overfilled with solutions with up to 2cm of loose sediment. It
never destabilised and gave me excellent control over stirring speed.)
|
|
|
XeonTheMGPony
International Hazard
Posts: 1636
Registered: 5-1-2016
Member Is Offline
Mood: No Mood
|
|
look at the price, and guess!
way to fix it is to dismantle it, and replace the magnet with a better / stronger type, but as J sum1 suggested try a better stir bar first.
For future reference any thing less then 500w will be a head ache for any complex or largis synth.
I would advise you invest in some quality insulating blankets.
I got an old corning with the same issue, it is in large part due to an aged magnet that is weak, some point I will replace it with a neo mag, and
same time get a new top plate with heater in it.
[Edited on 14-1-2020 by XeonTheMGPony]
[Edited on 14-1-2020 by XeonTheMGPony]
|
|
|
stephill92
Harmless
Posts: 23
Registered: 19-3-2019
Member Is Offline
|
|
Thanks for the replies, I'll definitely look into some new stir bars and an insulating blanket. Unfortunately for me I'm not very mechanically
knowledgeable so I don't exactly know what specifications to look for in a good hot plate.
I also found the same hot plate for various prices on amazon so I probably need to do a better job of figuring out what to buy.
|
|
|
G-Coupled
Hazard to Others
Posts: 287
Registered: 9-3-2017
Member Is Offline
Mood: Slightly triturated
|
|
There's an Indian seller who is selling some possibly decent seeming Indian made mantle/heater/stirrers at good prices in recent thread here.
|
|
|
Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
Quote: Originally posted by XeonTheMGPony  | | I got an old corning with the same issue, it is in large part due to an aged magnet that is weak, some point I will replace it with a neo mag, ...
|
I suggest that you use either AlNiCo or SmCo magnets as they have a much higher Curie temperature than NdFeB.
(AlNiCo magnets self-demagnetise more quickly than SmCo but can be fairly easily re-magnetised)
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
XeonTheMGPony
International Hazard
Posts: 1636
Registered: 5-1-2016
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Sulaiman | | Quote: Originally posted by XeonTheMGPony | | I got an old corning with the same issue, it is in large part due to an aged magnet that is weak, some point I will replace it with a neo mag, ...
|
I suggest that you use either AlNiCo or SmCo magnets as they have a much higher Curie temperature than NdFeB.
(AlNiCo magnets self-demagnetise more quickly than SmCo but can be fairly easily re-magnetised) |
Thanks will look into those!
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
