monolithic
Hazard to Others
Posts: 435
Registered: 5-3-2018
Member Is Offline
Mood: No Mood
|
|
Emulsions from MgSO4?
I get a persistent white emulsion every time I dry a compound with a particular brand of MgSO4. The bulk of the drying agent falls to the bottom or
swirls around like a snow globe, like it should, but some of it remains as a very fine, free flowing emulsion that takes forever to settle and
requires filtration through cotton to separate from the product. It's very annoying and I don't ever remember having this issue with proper lab grade
MgSO4 a decade ago in college? Is this normal?
|
|
|
Dr.Bob
International Hazard
Posts: 2658
Registered: 26-1-2011
Location: USA - NC
Member Is Online
Mood: No Mood
|
|
It may just have fines in the mix, MgSO4 is the fluffiest drying agent, so it could do that. If you get a granular form that has been sieved, it
won't contain them, but cheaper grades are a mix of particle sizes. Sodium sulfate is usually more crystalline, but it does not dry as well as
MgSO4. Mg can also chelate some functional groups, so that can also be a challenge, it binds well to some acids, alcohols, and other polar groups.
If you see the same emulsion in pure solvent, it is fines, if only with certain compounds, it might be some binding to the material in solution.
|
|
|
monolithic
Hazard to Others
Posts: 435
Registered: 5-3-2018
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Dr.Bob  | | It may just have fines in the mix, MgSO4 is the fluffiest drying agent, so it could do that. If you get a granular form that has been sieved, it
won't contain them, but cheaper grades are a mix of particle sizes. Sodium sulfate is usually more crystalline, but it does not dry as well as
MgSO4. Mg can also chelate some functional groups, so that can also be a challenge, it binds well to some acids, alcohols, and other polar groups.
If you see the same emulsion in pure solvent, it is fines, if only with certain compounds, it might be some binding to the material in solution.
|
Makes sense. I'm trying to use it on alkenes and amines, which I believe should be compatible with MgSO4. I'll try to find some fine sieves and remove
the fines. 
|
|
|
Dr.Bob
International Hazard
Posts: 2658
Registered: 26-1-2011
Location: USA - NC
Member Is Online
Mood: No Mood
|
|
Just take some and mix with a simple solvent like hexane, stir, decant the emulsion off, then dry the rest to use for real work. Or just filter
things after drying, I do that most of the time anyway if in doubt.
|
|
|
AvBaeyer
National Hazard
Posts: 644
Registered: 25-2-2014
Location: CA
Member Is Offline
Mood: No Mood
|
|
At the risk of being reprimanded I will ask: You are using anhydrous MgSO4 and not epsom salts? If anhydrous MgSO4, what supplier?
Also, MgSO4 is not really compatible for drying amines. Sodium or potassium hydroxides are the usual agents. You can find drying agent compatibility
and efficiency charts with a Google search.
AvB
|
|
|
monolithic
Hazard to Others
Posts: 435
Registered: 5-3-2018
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by AvBaeyer | At the risk of being reprimanded I will ask: You are using anhydrous MgSO4 and not epsom salts? If anhydrous MgSO4, what supplier?
Also, MgSO4 is not really compatible for drying amines. Sodium or potassium hydroxides are the usual agents. You can find drying agent compatibility
and efficiency charts with a Google search.
AvB |
Yes, it's anhydrous. Alpha Chemicals is the manufacturer.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
