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Author: Subject: Choosing best reflux column & condenser to order
International Hazard

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[*] posted on 15-7-2018 at 10:00
Choosing best reflux column & condenser to order

So I'm ordering some new parts for a distillation setup and I've never used a vigurex column before so IDK what size to order. I'm looking at 24/40 joint size and 100, 200 and 300mm columns. I'm thinking that this will most likely be used to distill ethanol (& other alcohols & solvents to break azeotrope). If a longer one is capable of doing this and more (other solvents/alcohols) that a shorter one is not capable of, then I think a longer one would be a better option, unless they are much less efficient or something.

I'm also looking at ordering a liebig condenser as min is too small. I have a few other very nice condensers, one is a cross between a graham & liebig (it has an outer water jacket and a coiled condenser running the length inside the condensation chamber) but it doesn't have ground joints which I find odd. So I'm wondering what is a good length to order. Any suggestions on length for this? There are 200-400 nicely priced as well as 600mm. IDK if you can go too big on the condenser or not. I won't be distilling anything that can solidify any time soon.

Also, the hose barbs on the condenser are listed at 10mm and IDK what size hose I should order. They have 9mm OD x 6mm ID latex hose. In the kits they sell (distillation setups) they have the same condensers with 10mm barb, and they supply "rubber hose" which looks like the same as what they sell individually. It would seem these are the same things and the 6mmID would have to stretch over the 10mm OD barb. Is that do-able with latex hose? Is this what I should order for the water supply?

[Edited on 7-15-2018 by RogueRose]
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[*] posted on 15-7-2018 at 11:41

I mainly use a 30 cm Dimroth condenser for refluxing. They are fairly cheap. Once in a while I wish I had a bigger one.... You can pretty much always stack condensers, but big condensers are nice to have. All of my borosilicate condensers are 30 cm.

I don't think you can really go too big on the condenser unless you are working with very small amounts of substances (or very expensive substances) or the condenser is just ridiculously huge.

For some reason, every reflux condenser I have bought has hose barbs that are just a little smaller than other condensers, so I use little gaskets cut from latex tubing to make sure that the hoses fit without leaks. If you put the gaskets on the condenser dry and then put dish soap on the outside, you can slide a PVC hose over them pretty easily. There are a ton of solutions for dealing with differently sized hose barbs.

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[*] posted on 16-7-2018 at 03:24

Reflux or product condensers have to remove heat at a rate equal to the power input to the boiling pot,
or vapour will be lost.

Efficiency of the condenser will depend upon geometry, coolant temperature and boiling points.

Condensers with thin walls or glass helices are more efficient than the basic Leibig type,
but more likely to break in the post or during cleaning/washing.

I find an air condenser useful for condensing high b.p. vapours,
and occasionally before a Leibig for 'free' cooling
and it can be used as a Hempel/packed column.

As examples, with water, ethanol etc. using c15oC cooling water;
A 2 litre pot on a 1.5 kW hotplate can overwhelm a 200mm effective length Leibig, at full power or if 'bumping'.
My diy 500ml mantle rarely overwhelms a 200mm Leibig.

Refluxing implies a lengthy procedure with un-attended periods,
so it is good to be confident that the condenser is very efficient.
My most efficient condenser is similar to a Dimroth type
There are better but so far the above three types do all that I need.
I think that the tubing type for the coolant depends upon circumstances;

on a tight budget - use whatever you can get your hands on

with a permanent space for the still - reliable, thick-wall pvc is a good choice

I need to prepare a space, set up the still, clean it and then pack it away,
I also use a water pump sometimes, and occasionally I will be using a heat exchanger, all have different connections,
so far 6/8mm pvc tubing has served me well.
I would like quick on/off adapters for all the plumping joints,
but for economy I use odd lengths of tubing to adapt the 6/8mm tubing to whatever,
small water pumps need one or even two smaller inner pieces,
some connections require tubing over the 6/8mm tubing,
the only benefit is that I can buy long lengths of 6/8mm pvc tubing fairly cheaply.
If this is your situation then the 'worst' part is when tubing gets 'stuck' on a glassware hose connector :mad:
- too scary to use much force with glassware
- annoying to store a condenser with a length of pvc tubing stuck to it
- very annoying to have to resort to cutting through the tubing then slice it off of the glass.
... and know that next time I will do the same again :P

EXTREMELY IMPORTANT : Refluxing and distilling take time, often un-attended for periods.
Imagine what would happen if the cooling failed - all vapour will escape
water can spray in any random direction.
if you expect to be away at times (at least toilet breaks)
make sure that your plumbing is secure.
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[*] posted on 16-7-2018 at 15:07

24/40 glassware is relatively large and sturdy. I received several 200 MM Grahams from Deschem, they were actually longer than expected. The 200 MM designation refers to the length of the cooling area, not to the total length of the condenser.

300 MM is more or less standard, 400 MM is available at a modestly higher price. Generally, if you go longer than 400MM, there is then a big price jump.

My experience with PVC, is if you preheat the end in boiling water, it will slip right on. When it cools, it will most likely stay put. And, yeah, if you want it off again... You may have to cut it off.

Latex tubing is easy to get on and off, and in-fact may remove itself at an inopportune moment. I'm used to working with Latex, but that could change. It is expensive.

My local hardware store, charges U.S. $2.50/Foot, for Latex tubing. In some circumstance, this might easily make the Latex tubing, more expensive than the Glassware set-up.

I have reached the same conclusion regarding adapters. It would be nice to have some.

Perhaps some plastic Automatic Drip System parts would be suitable.

Arrggg. Another trip to the Hardware Store/Garden Center.

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[*] posted on 16-7-2018 at 22:23

The only latex tubing that I have tried is the cheap stuff that came with my
eBay cheap Chinese "500ml Distillation Kit" - which is awful tubing,
so elastic that it can bend over due to the weight of water inside it and pinch the tubing closed,
causing the weakest part of the tubing upstream from the obstruction to inflate like a balloon !
or jump off of one of the hose connectors and allow water to shoot out ... free added excitement :P
- in the middle of a distillation :o

I suggest that anyone receiving similar tubing use it to make a catapult or something,
use it for anything other than its intended purpose.
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[*] posted on 17-7-2018 at 15:53

5/16 inch rubber vacuum line (or is it 1/4? Fuck) works great for water lines to condensers. Makes a good seal, goes on and off easy and is cheap and easily available. latex tubing is a pain in the but.

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[*] posted on 19-7-2018 at 12:06

For the length of the Liebig what kind temperature water do you usually use in the condenser? With 15-20 °C tap water my 400 mm Liebig was more than enough for anything I ever did. Distilling 1/2 liter of DCM was demanding I think but even then only 2/3 of the condenser were used.

Of course this also depends on what kind of flowrate goes through the condenser. If you use a 20 liter boiling flask a longer condenser is required than for a 500 ml one.

Another point to consider are mechanical losses. If you use a 600 mm condenser you will lose more product that sticks to the condenser.

Finally, if you use a long condenser it will be a pain in the ass to clean. Make sure it fits in your sink! When I tried cleaning my 400 mm one, it barely fit and I ended up accidentally breaking the joint on one side.

Also a Dimroth is not really useful in most cases. I have a 400 mm one but I only ever used the lowest quarter of it. Maybe its useful if you want to reflux bromine or ether. But better have ice water in a Liebig than 5 °C water in a Dimroth. Also, cleaning issues with Dimroth
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[*] posted on 19-7-2018 at 12:36

I don't recommend anyone try this, but can you imagine what might have happened with a Liebig:

Friedrichs condensers are even more efficient than Dimroths, and jacketed Dimroths are nice also... any non-Liebig condenser is harder to clean than a Liebig, but often Liebigs really aren't the best choice.

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[*] posted on 19-7-2018 at 12:48

Quote: Originally posted by Heptylene  

Also a Dimroth is not really useful in most cases.

To be clear, I completely disagree with this statement; a Dimroth really is useful in most cases.

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[*] posted on 21-7-2018 at 21:32

Hop on this fellas! killer price

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[*] posted on 22-7-2018 at 04:30

Quote: Originally posted by MöbiusMan  
Hop on this fellas! killer price

Looks sweet at first glance. But a couple of issues:
I would need an adapter for that 45/50 joint.
There is not ground joint on the top. Fine for reflux which is what it would generally be used for. But with a ground joint you would be able to feed the offgas into another reaction.

And then for me, shipping more than doubles the price. $167 AUD does not look like a bargain any more.
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[*] posted on 22-7-2018 at 05:52

I have 2 that are the same except they're mint Pyrex England...they were part of a lot and I've never used them. It would be nice to be needing those for 2-22 liter flasks but alas. IDK why the old ones have the stopper top, but with the ground joint they can be used for condensing if you rig things up right but it's inconvenient.

Most of my water connections are with natural latex, with a collar on the ends and sometimes rubber bands.

If one is a bit serious about fractionations, a search for vacuum jacketed columns should lead to useful glass. A long packed or unpacked column can always be pushed to inefficiency.

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