Is a 200mm liebig condenser long enough to condense say water/ethanol ect? The basics
Sorry as to I did not know which area this thread belongs in.ninhydric1 - 17-3-2018 at 19:07
It will be fine. If you are distilling low bp substances such as diethyl ether, run ice water. Otherwise such a condenser works for most
solvents/liquids.BromicAcid - 17-3-2018 at 19:20
A 200 mm liebig will provide X heat exchange where X is dependent on the condenser fluid (specific heat), the temperature of the fluid at the inlet,
and the rate of fluid flow. Obviously, a colder faster flowing fluid with a high specific heat would be a best case scenario.
Now, you need to evaluate the amount of heat you can remove X vs your rate of distillation and the specific heat of the material you are distilling.
If your rate is very high and your specific heat is very high it's going to be taxing for your condenser.
Essentially, you have control over many of these variables to some extent or another. You can make this condenser work for many situations but if you
are having issues look what variables could be adjusted. Usually though you take nearly all of these variables to be fixed and simply adjust your
rate of distillation, slower if you are 'overwhelming' your condenser. Time and your own experience will tell if you want to upgrade to a different
style condenser in the future. The next time you need a condenser you might think "this one worked fine, I want another just like it" or your might
thing "my distillations just went so slow, I should really get something better".Yttrium2 - 17-3-2018 at 19:28
Could 1 stand and clamp support a distillation setup?
I used to have a 400mm condenser and I remember condensate making it 1/2 to 2/3rd's the way down the condenser. Hmm.
Would another factor that influences how far the vapor moves before condensing be the size of the boiling flask? How much is being boiled.
Forgive me if these questions sound ridiculous, I had it in my mind that a 400mm condenser was necessary at the least. Will be getting another kit,
likely.
Any ideas as to how long a piece of tubing would need to be to have a lot of materials air condense? Thinking perhaps a flask with a rubber stopper
and a long lenth of tubing might be good. Though I'm not sure about what diameter/thickness would be best and I'm not sure if I could tightly fix a
balloon over smaller diameter than 24/40 tubing.
Thanks
[Edited on 3/18/2018 by Yttrium2]DavidJR - 17-3-2018 at 19:44
Yes, it is possible to use a single stand and clamp, though it's not ideal. Clamp the condenser in the middle and use keck clips to hold everything
else. j_sum1 - 17-3-2018 at 20:02
I wish I had a 200mm or even 150mm. I have a 300 which is often more than what is required. I also have a short path which I love using when it is
appropriate.
The thing about condensers is that you can often substitute or configure two together. And it is always better to have more than one available. So
start with a 200. Then add a dimroth or friericichs and a vigreux. Then a big liebig, a short path and leave the graham until you need something
oriented vertically.
Edit
An air condenser is also worthwhile at times.
[Edited on 18-3-2018 by j_sum1]Tsjerk - 18-3-2018 at 00:39
I love my 300 mm vigreux air condenser, when it is not too hot outside it is fine to do refluxes with not too low boiling solvents. Water e.g.
perfectly condenses in it, so no hassle with water pumps and stuff. I never used it as condenser in a distillation, but I guess that should also work
fine. Sulaiman - 18-3-2018 at 01:21
As mentioned above,
all of the heat used to vapourise the liquid has to be removed by the condenser,
so if your heater-flask combination at full power needs a 400mm condenser,
then for a 200mm condenser use 1/2-power,
it will take 2x longer for the distillation.
OR add a second 200mm condenser.
Air condensers are required when boiling points are above the b.p. of water,
for low b.p. liquids like ethanol, ether etc. air condensers are not efficient per unit length,
e.g. I guestimate that for ethanol,
a 200mm water-cooled leibig is equivalent to an air codenser of one or two metres of glass tubing,
depending upon local ambient temperature,
and if you live in a hot climate,
it is impractical to use an air condenser for 'low' b.p. liquids such as diethyl ether
or, if you live in antarctica, an air condenser would be ideal, as water freezes
Also, if you have a nice steady boil-up rate then you will see in the condenser where the last vapour is condensed,
if there is any 'bumping' in the boiling pot you will see the vapour front surge - past the end of your condenser out of your equipment to be lost.
For the majority of distillations, a water-cooled condenser is required,
and its 'cooling power' should be greater than the effective 'heating power' for the pot.
So
. too much condenser power is better than not enough,
. a larger condenser allows faster throughput
. condensers can be combined in series
As we do not know your effective heating power a definite answer cannot be given,
I think that a 200mm Leibig condenser is adequate for most amateur distillations,
but, if you have the space and clamps, 300mm, 400mm 2x200mm etc. is better.
...........................................................................................
I would not use one clamp to hold a complete distillation rig,
partly due to the stresses on the glass,
but mainly because I do not trust keck clips enough to suspend thin glass flasks of boiling flamable solvent.
Clamps and stands are not cheap
for a simple distillation kit I use two stands with clamps
which together cost about the same as the simple Chinese glassware distillation kit.
The good news is that retort stands and clamps are also useful for holding;
. washed glassware to dry
. thermometers in flasks
. miscellaneous objects for gluing, painting, soldering......
Even without chemistry as a hobby I should have bought stands and clamps many years ago as they are generally very useful as a third or fourth hand..
P.S. just a personal thing,
I am moving to using product condensers vertically oriented,
in my case by using one of these https://www.ebay.co.uk/itm/19-26-24-29-29-32-Joint-105-to-75...
this allows one (sturdy) stand with multiple clamps to accomodate a distillation rig with reflux using less bench space.
[Edited on 18-3-2018 by Sulaiman]Yttrium2 - 18-3-2018 at 07:26
This may be off topic, and contributing to a thread many others may wish to see dead (I'm fearful) but, why in the world would one want to use a
graham condenser?
I've been over this several times, but for some reason it's eluding me.
I'm also wondering about the utility of a single retort. It doesn't seem like a lot of them have very long condensers.
Also wondering about improvised uses of common glassware pieces. Is there anything besides packing a liebig full of dry ice and using it as a dry ice
condenser ? Heh
[Edited on 3/18/2018 by Yttrium2]UC235 - 18-3-2018 at 07:55
This may be off topic, and contributing to a thread many others may wish to see dead (I'm fearful) but, why in the world would one want to use a
graham condenser?
Graham condenser is good for one thing and one thing only. Downward distillation of low boiling solvents. It offers extremely efficient cooling with a
very high ratio of coolant to surface area and the spiral shape introduces plenty of nonlaminar flow to ensure the vapors contact the condenser walls.DavidJR - 18-3-2018 at 09:38
I would not use one clamp to hold a complete distillation rig,
partly due to the stresses on the glass,
but mainly because I do not trust keck clips enough to suspend thin glass flasks of boiling flamable solvent.
Most often I use a flat-bottomed flask or erlenmeyer flask as the boiling flask, placed directly on the hotplate/stirrer. This means that the boiling
flask isn't just hanging by the keck clip. The receiving flask should hopefully not be boiling...
Even when using two stands, I don't usually clamp the receiving flask, primarily so that it's easy to switch receivers etc. I usually clamp the vacuum
adapter and the stillhead.
Then again my biggest flask is 500ml (and I more often use 250ml flasks), but if you were using bigger/heavier flasks full of dense substances it
might be wise to clamp the flasks.Magpie - 18-3-2018 at 11:57
I use a 20cm condenser almost exclusively. Use ice water if needed.
