Nitrox2 - 13-6-2025 at 11:13
Lets say there is this flask, connected by 150mL round bottom flask and stopper.
The pear flask is heated till vapor passes through the side arm, and the 150mL round bottom flask, is submerged in dry ice and acetone.
If there if 5mL of a substance in the pear flask, that boilings at 235c, would much of this compound come over into the dry iced cold flask?
How much, and at what temperature? -- For how long??
[Edited on 13-6-2025 by Nitrox2]
jackchem2001 - 13-6-2025 at 22:13
If I understand your post correctly, you might crack the glass doing that. Why such a low temperature for a high boiling compound?
MrDoctor - 14-6-2025 at 01:43
if it boils at 235C it would migrate over even like 50 degrees below its boiling point. if you planned on sealing this once its going, thats probably
a bad idea, unless its under a reliably sealed vacuum.
As for how much, its impossible to know since you havent specified what it is. but the math will work out something like, what is its volume in vapor
phase at that given temperature, then subtract the volume of everything up to the side arm. distillation requires that your liquid become a gas, and
that gas then probably being heavier than air, spills over into the cooled section, condensing. the problem though is that the vapor must carry itself
there.
it may be better to instead steam distill it then solvent extract from the water, if it is something that can be steam distilled
Nitrox2 - 25-6-2025 at 04:39
https://en.wikipedia.org/wiki/Icyball
[Edited on 6-25-25 by Nitrox2]
Radiums Lab - 25-6-2025 at 12:45
Can you give a hint about anything atleast its MW.
Radiums Lab - 25-6-2025 at 12:51
And remember VP is inversly prop. to BP. Try vaccum distillation this temp is high for boro glass.
[Edited on 25-6-2025 by Radiums Lab]
Chemister - 19-8-2025 at 23:09
I assume this question is meant to determine of the absorbent liquid will end up inadvertently transferring over to the cold end of the icyball.
In theory all of it would come over given enough time, but in practice, on a reasonable timescale, very little, if any would actually come over.
The vapor pressure of a liquid at room temperature will be lower than the vapor pressure of a liquid at dry ice temperatures, meaning that any liquid
will evaporate from the warm end faster than it will at the cold end leading to a net transfer of liquid. However, a liquid with a boiling point of
235C likely wont evaporate at an appreciable rate at room temp meaning that even if it will eventually all transfer to the cold end, it would take so
long that there might as well not be any transfer happening at all. Also, I believe that when the the low boiling point refrigerant boils and goes
back into the warm flask it should be able to carry some of the high boiling absorbent with it, which should help if anything does come over on
accident.
For anyone else reading this thread, an Icyball is a type of refrigerator which uses a heat input to cool things down rather than mechanical work. It
works on the principle that if you mix a liquid with a low boiling point like ammonia with a liquid with a higher boiling like water, it will raise
the boiling point of low boiling point liquid. An Icyball simply consists of two sealed containers connectedtogether, one containing ammonia, one
containing water. The ammonia boils, cooling off its container, and the ammonia vapor condenses into the water and is sequestered . Once the ammonia
is absorbed by the water it will have a much higher boiling point which means that it won't be able to evaporate transfer heat back to the cold side
which is what allows more ammonia to evaporate from the cold side. Note: The absorption of ammonia vapor into the water generates heat meaning that
this device effectively moves heat across a temperature differential rather than simply absorbing heat.
The reason that this is useful is that the system can easily be regenerated by heating up the water ammonia mixture in the water side, while cooling
the now empty ammonia side to distill the ammonia off from the water. This should work with liquids other than water and ammonia as long as they have
a significant difference in vapor pressure, but water and ammonia work particularly well due to ammonia's high heat of evaporation and vapor pressure,
and water's low molar mass. I assume that the author of this post is probably trying to do this with an absorbent liquid with a boiling point of 235C
and is trying to make sure that it wont come over into the cold flask.
Side note: I would strongly recommend against trying to make a glass icyball. Generally icyballs need to be completely sealed, and
have significantly different internal pressure depending on the temperature of the system (e.g. pressure is different when cooling vs recharging)
meaning that there is a good chance that you will end up pressurizing your system excessively. This could have a range of outcomes from sending your
glassware across the room to having your system explode and spray glass shrapnel everywhere. Even if the system isn't pressurized, it will at the very
least need to be held under vacuum, and with the temperature differential you are suggesting the glassware is likely to break, which would likely lead
to an implosion, glass shrapnel, etc as well.
Dr.Bob - 20-8-2025 at 17:44
A kugelrohr apparatus (google it) is a simpler way to do what you are thinking, and works well for high BP compounds. I have used them often (and
have glass bulbs for the process if you need any) and they can handle heating one bulb while cooling the other to -80C just fine. That can allow for
ditillation of tiny amounts in good yield (80%). It can even go up to larger amounts, but mostly is used for under 50g in my experience.