LuckyWinner
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When to use an Air Condenser and when Water in Condenser ?
at what specific temperatures should you use an air condenser,
with air condenser I mean a liebig where you pump air through with an aquarium air pump.
what boiling temperature should the liquid be?
for what boiling temperature would you use regular tap water ~18C,
and when to use ice water in your condenser.
I looked but could not find the exact numbers.
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Antigua
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You will not find exact numbers. You should use an air condenser if you're distilling small amounts of high boiling components. The condenser can get
easily overloaded if there's too much substrate.
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LuckyWinner
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Quote: Originally posted by Antigua  | | You will not find exact numbers. You should use an air condenser if you're distilling small amounts of high boiling components. The condenser can get
easily overloaded if there's too much substrate. |
my main worry would be a too high of a heat difference between condenser tube and coil which would cause the condenser to crack...
is this even possible at the usual 150C vapor and icewater contrast at ~5C condenser coolant?
thats 145C difference
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macckone
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LuckyWinner,
160C is the differential recommended by ace glass for thermal shock resistance.
Borosilicate is not recommended for continuous service above 200-230C.
However it should be able to handle excursions to 400C.
The strain point is 515C, heating above that will require re-annealing.
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Fyndium
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You can use air cooled condenser for stuff over 160C and then a water cooled graham to cool down the still hot liquefied condensate. For middle term,
you can use air pump to run air as coolant. Dual condenser setup with trap is also good in other circumstances, like vacuuming not-so-high bp
solvents, and at ntp for highly volatile stuff like ether, which you first condense with normal water, and then cool it down in graham with cryogenic
coolant(icewater, salt-ice-water, CaCl2 water, etc) to crash the vapor pressure.
The condenser temperature gradient doesn't have to be big at all, 30-50C is well enough. Room temp water will condense acetone, although it is wise to
put the receiver flask in cold bath. For water and other similar BP distillates even hot, 50-60C water is well enough. Extra power helps only to
remove energy from the condensate, but this causes temp stresses in the condenser and can even break it, and it is indeed wiser to use cold bath for
the receiver flask and/or secondary condenser instead.
I prefer dimroth condenser in place of liebig. It has air cooled outer wall, and water cooled coil, and the total surface area is huge compared to
liebig. Even small, 200-300mm dimroths are able to condense several liters of acetone per hour with ease. I don't even have liebig at my home lab,
only dimroth, which can be run as condenser, reflux, fractionating column, etc. Only issue could be when distilling something that has high melting
point, which would accumulate to the coils, but on the other hand, people have used this to purify stuff by sublimation like sulfur.
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