Drone
Harmless
Posts: 12
Registered: 20-11-2005
Location: UK
Member Is Offline
Mood: No Mood
|
|
Breaking emulsion between Water and DCM
Hi,
In trying to extract Caffeine from Coffee I prepared 100ml of a strong solution of Coffee. I then washed this with 3*25ml portions of Dichloromethane.
During this I noted that there was a slight emulsion forming at the boundary of the two solvents. At this point that my 75ml of DCM had a layer of
about 5ml of Coffee on it.
In a (misguided?) attempt to remove this I added 50ml of saturated NaCl solution to the DCM and shook it together. This resulted in what looks like a
homogenous emulsion of DCM and H2O. On closer observation the fluid feels 'foamy' and is a very intimate mix of DCM and H2O.
I have searched but have been unable to find any hint of a method to break such an emulsion.
Does anybody here have a method to separate the DCM from such a mix?
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
Try a few drops of conc. H2SO4.
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
BromicAcid
International Hazard
Posts: 3227
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
Usually the washing with a saturated salt solution is used to remove water from the non-aqueous phase. However in this case you increased the density
of the water, bringing it closer to the density of the dichloromethane and therefore increased the propensity to form an emulsion. I never heard of
the sulfuric acid trick before, I once had my two phases stuck as an emulsion and they separated, for the most part, over the course of 48 hours.
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
I'm not saying that the H2SO4 will work for everything but it did the job nicely for an application at a pulp mill. We had a neat little decanter
(Venetian?) that would automatically separate water from terpentine in the digester blow condensate. Eventually crud (an emulsion) would build up at
the interface between the organic and the water, interfering with a clean separation. We would dump in a liter or 2 of con. sulfuric acid into the
decanter. This would break up the emulsion right away.
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
vulture
Forum Gatekeeper
Posts: 3330
Registered: 25-5-2002
Location: France
Member Is Offline
Mood: No Mood
|
|
Take a funnel, jam a piece of cotton in the neck, fill the funnel with MgSO4/Na2SO4/etc and allow your emulsion to drip onto it. Flow rate is slow, so
I suggest you use a separation funnel.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
