Yttrium2
Perpetual Question Machine
Posts: 1104
Registered: 7-2-2015
Member Is Offline
|
|
When water boils
When water boils under vacuum,
--
Does the vacuum level change (amount of suction)?
Its been a while since I studied gas laws, and I only got a bit of an understanding of it, but im trying to understand how vacuum distillation works
|
|
|
Ubya
International Hazard
Posts: 1232
Registered: 23-11-2017
Location: Rome-Italy
Member Is Offline
Mood: I'm a maddo scientisto!!!
|
|
amount of suction is not a real measuring unit 
when water boils under vacuum it is because the vapour pressure at that temperature is the same as the pressure over the liquid. if you where to
apply a vacuum until the water boils, and then close the system, the pressure inside the vessel would be the same as the vapour pressure of water at
that temperature, if the vapour increases the pressure, the water will stop boiling, so it it an equilibrium point.
if by amount of suction you mean the amount of mass flowing out of the system yeah of course it will increase as water is increasing its volume by
going to the gaseous phase, so a higher volume flow of gas will "boil" the water faster (remember that the temperature will drop, so the vacuum also
drops)
---------------------------------------------------------------------
feel free to correct my grammar, or any mistakes i make
---------------------------------------------------------------------
|
|
|
mackolol
Hazard to Others
Posts: 458
Registered: 26-10-2017
Member Is Offline
Mood: Funky
|
|
Vacuum is the power of suction but there is also speed of the suction to achieve that vacuum.
If one were to present it on an example of vacuum pump parameters are for example max vacuum: 700mmhg and also flow speed for example 23l/min, bigger
pumps can achieve for example 60l/min
|
|
|
chornedsnorkack
National Hazard
Posts: 522
Registered: 16-2-2012
Member Is Offline
Mood: No Mood
|
|
Liquids, especially in vacuum, tend to boil under nonequilibrium conditions. How does the pressure in headspace change as the boiling liquid bumps?
Between the bumps? What does te temperature do?
|
|
|
mackolol
Hazard to Others
Posts: 458
Registered: 26-10-2017
Member Is Offline
Mood: Funky
|
|
Quote: Originally posted by chornedsnorkack  | | Liquids, especially in vacuum, tend to boil under nonequilibrium conditions. How does the pressure in headspace change as the boiling liquid bumps?
Between the bumps? What does te temperature do? |
When I'm vacuum distilling pressure stays constant for most of the time. It doesn't change when it bumps. When I distill volatile solvent, my pump
pulls weaker vacuum, but as the distillation progresses it goes higher. And the temperature just does the same as with normal pressure. It just
requires lower temperature to boil under vacuum.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
