ampakine
Harmless
Posts: 25
Registered: 29-4-2011
Member Is Offline
Mood: No Mood
|
|
Salting out isopropyl alcohol
I read on its wiki page that isopropyl alcohol is far less soluble in saline water than pure water and will form its own layer when salt is added to a
concentrated IPA solution. I tried this just there but could not see any layers. I considered that it may just be difficult to see because they are
both clear and colorless liquids but I've seen bilayer mixtures of white spirit and water before and remember the interphase between the 2 layers
being highly visible. Is it just harder to see the interphase between these 2 solvents because they are so similar in molecular weight?
[Edited on 19-7-2011 by ampakine]
|
|
|
gsd
National Hazard
Posts: 847
Registered: 18-8-2005
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by ampakine  | Is it just harder to see the interphase between these 2 solvents because they are so similar in molecular weight?
[Edited on 19-7-2011 by ampakine] |
???
Water - H2O - MW:18
IPA - CH3CHOHCH3 - C3H8O - MW:60
If you are unable to see layers then the simple explanation is they are not yet formed.
Just keep adding more salt till you see the separation.
gsd
|
|
|
cyanureeves
National Hazard
Posts: 737
Registered: 29-8-2010
Location: Mars
Member Is Offline
Mood: No Mood
|
|
true i didnt see any layers form either so i assumed all the water was in the salt slurry. i added about a quarter ways up of salt in a bottle of 91%
isopropyl and syphoned out the alcohol and stopped before i got to the salt.
|
|
|
HexJam
Harmless
Posts: 25
Registered: 29-9-2008
Member Is Offline
Mood: Steady
|
|
I've seen IPA split into 2 layers if you use MgSO4, however they're -very- difficult to spot. I remember trying this a while back and totally missed
seeing it the fist few times and was baffled what was going on. Try leaving your beaker to sit and settle for a while then very gently swirl it to
help you see the layers, your water might also just be a small clear blob on the bottom of your flask.
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
NaCl will only remove water up until ~91%. After that, you need to switch to NaOH. See http://www.sciencemadness.org/talk/viewthread.php?tid=13680
Difficulty in seeing the difference between phases comes from similar indexes of refraction.
[Edited on 7-22-11 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
FrankRizzo
Hazard to Others
Posts: 202
Registered: 9-2-2004
Member Is Offline
Mood: No Mood
|
|
I believe a laser pointer aimed through the solution could show you the boundary. There should be a slight bend in the line of light as it hits the
boundary.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
