Sciencemadness Discussion Board

Wrong/Bad Condensor with Soxhlet Extractor

electrokinetic - 4-3-2021 at 11:38

I am looking to acquire a Soxhlet Extractor and found some on ebay that come with flasks and a condensor.

Listing 1

Listing 2

I don't have much experience with apparatus like this so I thought I'd ask: the first listing comes with a Graham condensor. But Grahams should be avoided for reflux, yeah? So it's better to go with something like listing 2?

Thanks.

Fyndium - 4-3-2021 at 11:43

I wonder it too why they sell graham condensers for reflux. I've tried it once, because that's what I got at hand then, and it almost ended up jumping to trash bin by itself due to reflux choking it and causing pressure buildup. It was sheer luck I stood next to it when it choked and I just grabbed it until it popped up.

Grahams are great for low boiling liquid condensers and post-coolers after primary condenser both for reflux and distillations, but never as reflux.

Soxhlet usually is supplied with Allihn condenser.

Dimroth or just coil condenser is my favorite all-purpose condenser. It has very large surface area and it also benefits from air-cooling of outer wall so it is very hard to overrun, and it is also hard to choke and it can be used in any configurations possible. Acetone vapors came partially through a liebig, but coil just condensed them all 1/3 way and had no issues when running it even a lot faster. I've got three of them, and have since used my liebigs only when I needed to run multiple condensers for some reason.

[Edited on 4-3-2021 by Fyndium]

electrokinetic - 4-3-2021 at 14:37

Dimroths are fantastic. I have one that is 19/22, and was hoping to find an appropriately sized Soxhlet to go with it. I found one, but it looks like the male and female ends are reversed. I would have no idea how to hook that up—I've never seen a boiling flask with a male joint. Am I missing something simple?

[Edited on 4-3-2021 by electrokinetic]

Fyndium - 4-3-2021 at 17:10

Just order adapter from China. Costs 4€.

electrokinetic - 4-3-2021 at 20:18

Quote: Originally posted by Fyndium  
Just order adapter from China. Costs 4€.


That is pretty simple. Thanks.

XeonTheMGPony - 5-3-2021 at 03:32

what I did, ordered an adapter to 24/40 and used my Allihn @ 300mm for it, Now I have a Dimroth I'll be using that next run.

Dr.Bob - 5-3-2021 at 04:16

You are correct that a Graham is not good for this type of use, it will limit your distillation rate severely.

The two links are also different sizes, the larger ones are often better as you can always use a large one with less material, but overloading one will usually be a mess.

For people in the US, I still have these in small, medium, large and huge sizes, in US made glassware in used but very good condition. The prices are similar to the chinese prices, but the quality is better.

zed - 6-3-2021 at 21:00

Don't buy those sets, if you can help it. Think it out first.

I bought a Soxhlet set, dirt cheap a while back. 24/40 at the bottom of the reciever and 45/50 at the top. Then, I bought a 45/50 to 24/40 adapter to mount a condenser. I used Deschem.

Here is the rational. The Graham Condenser is generally useless as a reflux condenser. Too small a bore, and too efficient. The condenser gets plugged up with solvent, pressure builds up, and solvent blows out the top of the condenser. If you are working with something like Ether, this could cause a fire and explosion.

Now, if you are working with the included Allihin, and you are refluxing water, that is fine. But, once again, if you are refluxing something like Ether, there is danger. The Alihin is a good reflux condenser, but it is inefficient.
You will lose a lot of Ether as vapor. Explosive Vapor.

The top of the standard Soxhlet condenser, does not have a joint attached. Straight tube. That's it. You cannot back-up the Allihin, or use the Graham for what it is good at....downward distillation.

If you can just buy the bottom half of the Soxhlet (cheap), and an adapter, you are better off. You will be completely free
to mix and match, as you like. You could use a 24/40 Allihin as your primary condenser, and fit a 24/40 Graham on top of it, as a scavenger. You can also attach a 24/40 drying tube. Or, you can just use a much better condenser, like a 24/40 Friedrichs.

More versatile, is more better.

A friend chemist with Soxhlet problems, once blew up a building that way. Losing Ether, while conducting a reaction, under a Soxhlet. He attached a long tube to the top of his (un-jointed) Soxhlet condenser to conserve solvent. It didn't work very well, he kept losing solvent. Eventually, the reaction got hot, and he lost more solvent.

The reaction ran away. Pressure built up. Cooling the flask, did not help. It kept getting hotter. Vapor and Hydrogen gas, forced its way out of the flask, and there was a very impressive detonation. He wasn't killed because he had wisely run for his life. But, it was a hairy, expensive mess. And, the whole debacle might have been avoided, if he had been able to attach better condensers to his Soxhlet Extractor.

If you are American, 24/40 is standard here. In other parts of the World, 24/29 is more standard. They are somewhat compatible.... Usually. 24/40 is slightly more expensive.

Don't get stuck with a lot of stuff in odd sizes. An odd sized adapter, may cost more than the item it adapts to.





[Edited on 7-3-2021 by zed]

[Edited on 7-3-2021 by zed]

[Edited on 7-3-2021 by zed]

[Edited on 7-3-2021 by zed]

electrokinetic - 7-3-2021 at 11:29

@Xeon thanks and good luck. I'd rather get one where I can use my dimroth (or my Friedrichs as well)

@zed solid advice thank you, I'll keep looking

XeonTheMGPony - 8-3-2021 at 03:42

Quote: Originally posted by electrokinetic  
@Xeon thanks and good luck. I'd rather get one where I can use my dimroth (or my Friedrichs as well)

@zed solid advice thank you, I'll keep looking


either way as said, get an adapter from the soxhlet to the size of ground joint you use was cheap and worked quite well

electrokinetic - 8-3-2021 at 08:57

Quote: Originally posted by Dr.Bob  
You are correct that a Graham is not good for this type of use, it will limit your distillation rate severely.

The two links are also different sizes, the larger ones are often better as you can always use a large one with less material, but overloading one will usually be a mess.

For people in the US, I still have these in small, medium, large and huge sizes, in US made glassware in used but very good condition. The prices are similar to the chinese prices, but the quality is better.


I'm interested in checking out your wares. PM sent