01-25-03 13:17
No 401443
This is kind of a newbee question, but I wanted to get some clarification nonetheless....It's been a while since I've taken a chem class, but I have read Zubrick from front to back and spent countless hours on TFSE....Is the Bleed/Inlet Tube necessary for a vac distill?...Zubrick says it is not needed if boiling stones or a stirbar is used, but I just want to be sure because for a simple distill he says to leave the vacuum adaptor open to the air "or the whole thing will explode"...now I know a vacuum means the abscence of air, but won't the whole thing explode here too?...Also, if needed, how open should the screwclamp be?
(Hive Bee)
01-25-03 13:30
No 401448
You have to mix your solutiont that you want to distill, inlet tube (gas bubbling), boiling stones, mag. stirbar.. it doesnt matter.
And you must not hermeticly attach reciving flask to the condenser, pressure will rise and than it can explode!
(Newbee)
01-25-03 21:24
No 401537
if you are doing a simple distill with out vac. you leave the vac. takeoff nipple open on your 105deg vac adapter. as a vent. or run a hose from it down your drain to get rid of any smells.
use a stir bar and you won't need a bleeder
(Hive Addict)
01-27-03 11:52
No 401938
You have a somewhat evacuated distillation setup, meaning the pressure inside of it is less than the outside pressure. How is that going to explode? If anything it would implode, but no, it won't under your vacuum distillation conditions.
(Hive Bee)
01-28-03 05:51
No 402111
Is the Bleed/ Inlet Tube necessary for a vac distill?...
Not if you use rapid magnetic stirring to prevent bumping (superheating) of the liquid. The capillary inlet for vacuum distilling is rather old-school, and magnetic stirring really is the go.
Zubrick says it is not needed if boiling stones or a stirbar is used
Boiling chips generally don't work well with vacuum, as the air which acts as a seed for vapour bubbles in the liquid gets sucked out.
for a simple distill he says to leave the vacuum adaptor open to the air "or the whole thing will explode"
For atmospheric distillation (a.k.a simple distillation) the distillation apparatus should be open to the atmosphere. Sealing it will cause it to pressurise as the liquid heats, hence the warning.
now I know a vacuum means the abscence of air, but won't the whole thing explode here too?
No, it won't explode. The vacuum pump keeps the pressure inside the apparatus low, hence no pressure can build up, so no explosion.
...Also, if needed, how open should the screwclamp be?
If you really must use a drawn out capillary to prevent bumping, then you adjust the screw clamp so that a thin stream of bubbles enters the liquid. Vogel suggests it takes practice to draw out a capillary tube to the right diameter.