Sciencemadness Discussion Board

Attaching 24/40 glassware joints to non-jointed flasks

SuperOxide - 26-11-2021 at 10:24

My largest jointed flask is a 24/40 2L erlenmeyer flask, and I love this thing. I like using it for any reactions that have large reaction mixtures yet low returns (aniline, toluidine, benzyl chloride, etc). I don't have anything larger than 2L, but if I wanted to get something larger, I might have to settle for something without a ground glass joint (since I'm mostly looking for stuff from domestic ebay sellers).

Most of the erlenmeyer flasks can use #10 rubber bungs which I could drill a hole in or even buy them pre-drilled (like this one). But usually the holes are only wide enough to accept a thin tube or something, not quite wide enough for a 24/40 or even just 14/20 joint.

I was curious if anyone here has a solution that might be a little more sturdy? I can't help but think that attaching a 24/40 condenser via a rubber bung might be a little sketchy. But I could be wrong.

If anyone has done this and has pics, please share :-D

Belowzero - 26-11-2021 at 12:15

In this case I use large rubber stoppers, brewery supply stores sell these, at least around here.
The stoppers have a slight angle which allows them to fit various sized flasks.

They stoppers come with or without holes.
A regular wood drill is quite effective for drilling those.
I have a couple lying around which have a glass tube fixed in the hole which has the correct diameter for fitting rubber hoses.
The disposable glass pipets I have are the perfect diameter and are quite capable of handling heat.
Easy and cheap solution.

Another solution would be to drill a large hole and fit a ground glass adapter in the stopper and work from there.



[Edited on 26-11-2021 by Belowzero]

Sulaiman - 26-11-2021 at 13:59

A direct glass-to-metal joint is difficult due to differences in thermal expansion rates,
So some type of rubber or plastic is required,
rubbers and plastics are often incompatible with various chemicals and/or high temperatures.
So it depends upon what you intend to do.

Various members have at various times offered to make and sell ptfe bulkhead-to-ground glass joint adapters,
but I've not seen any finished products.

One option is to fit a metal tube to the metal vessel
and a gas adapter to the glassware,
with suitable tubing between the two (pvc, silicone, ptfe etc.)

macckone - 26-11-2021 at 16:40

There are rubber and silicone vacuum filtration adapters.

Rubber:
https://www.amazon.com/Filter-Adapter-Buchner-Funnel-Tapered...

Silicone:
https://www.amazon.com/Rainbowrock-Adapter-Cone-Silicone-Sto...

You can also buy various polymer kits to make your own.

And of course you can use teflon tape either by itself or to wrap rubber, cork or silicone with.
And last you can use kapton film, also sold as roasting bags for turkeys.

macckone - 26-11-2021 at 20:23

A side note, this depends on how air tight you need it to be.
I have a high heat fused quartz rig that I interface with a regular condenser but
I use fiberglass rope for the seal. I use it for distilling H2SO4.
The fiberglass rope isn't 'air tight' but it does keep the H2SO4 on the inside.

Note this is a transition from an air condenser to a water condenser so there isn't a lot of vapor.

For the OP use I would say something made of or covered in teflon is going to work better.

If using metal containers and needing an air tight seal, I use exhaust system sealing putty.
It will eventually crack but it is cheap enough for single use applications.
The wrap it with teflon tape trick is useful at temperatures below 200C.
You can wrap a rubber stopper in teflon tape and it effectively becomes a teflon stopper.

draculic acid69 - 27-11-2021 at 01:20

Quote: Originally posted by Sulaiman  
A

Various members have at various times offered to make and sell ptfe bulkhead-to-ground glass joint adapters,
but I've not seen any finished products.


That's bcoz of the Teflon porn curse. Anyone advertising Teflon adaptors
and posting pictures disappears never to be heard from again.

[Edited on 27-11-2021 by draculic acid69]

Sulaiman - 27-11-2021 at 04:12

Just remembered :
I have two sizes of ptfe adapter for overhead stirring, a 24/29 for my diy overhead stirrer,
and my 19/23 was advertised as a thermometer holder - which is actually what I use it for.
Either can grip 7mm od borosilicate tubing, and seal into round holes.

SuperOxide - 27-11-2021 at 07:50

Quote: Originally posted by macckone  
There are rubber and silicone vacuum filtration adapters.

Rubber:
https://www.amazon.com/Filter-Adapter-Buchner-Funnel-Tapered...

Silicone:
https://www.amazon.com/Rainbowrock-Adapter-Cone-Silicone-Sto...

You can also buy various polymer kits to make your own.

And of course you can use teflon tape either by itself or to wrap rubber, cork or silicone with.
And last you can use kapton film, also sold as roasting bags for turkeys.


So I actually forgot I had those, and I use them for vacuum filtrations, and they work well (I've only ever had like 2 in use at a time, max). But this is more for things like refluxing, not even distillations.
Quote: Originally posted by macckone  
A side note, this depends on how air tight you need it to be.
I have a high heat fused quartz rig that I interface with a regular condenser but
I use fiberglass rope for the seal. I use it for distilling H2SO4.
The fiberglass rope isn't 'air tight' but it does keep the H2SO4 on the inside.

Note this is a transition from an air condenser to a water condenser so there isn't a lot of vapor.

For the OP use I would say something made of or covered in teflon is going to work better.

If using metal containers and needing an air tight seal, I use exhaust system sealing putty.
It will eventually crack but it is cheap enough for single use applications.
The wrap it with teflon tape trick is useful at temperatures below 200C.
You can wrap a rubber stopper in teflon tape and it effectively becomes a teflon stopper.

The only time I plan on using this is for reactions that have a large volume but a relatively small return (think aniline, toluidine, benzyl chloride, etc). So I would use this for the reflux part, then I could separate off the desired layer, and bring that to a much smaller flask (probably 1L).
Quote: Originally posted by Sulaiman  
Just remembered :
I have two sizes of ptfe adapter for overhead stirring, a 24/29 for my diy overhead stirrer,
and my 19/23 was advertised as a thermometer holder - which is actually what I use it for.
Either can grip 7mm od borosilicate tubing, and seal into round holes.


Interesting. I know I could get a female 24/40 for the male end of the condenser, and bring that down to a small diameter that would fit in a rubber bung with a small hole in it, but I wasn't sure how well refluxing such a large volume through a small hole.

Do you have pics?

SWIM - 27-11-2021 at 23:03

Just for context, how big a flask are we talking about here?

Refluxing several liters of something through a little tube may lead to solvent 'spitting' out the top of your condenser, or possibly the 24/40 condenser just filling up with solvent and overflowing.

As Belowzero said, those rubber stoppers are easy to drill out.

And, somewhat ironically, below zero is a good temperature to have your stopper at when you drill it. Leave it in the freezer overnight.

I'd try drilling one out to 7/8 inch. That ought to fit okay for a 24/40 joint. You can taper the top of the hole a bit by wrapping sandpaper around the 24/40 male joint and sticking it in there and working it around if you need to.
Start with a single hole stopper and you've got a pilot hole that'll help ensure a straight, true and centered hole.



[Edited on 28-11-2021 by SWIM]

Organikum - 27-11-2021 at 23:05

Drilling holes into rubber stoppers was always a major pain in the ass and I never achieved the results I hoped for. But I found happiness with good ol' cork which is easy to work with and I found out that when I wrap the cork stopper through the hole with the better quality PTFE tape (12 mm wide and thicker and denser then the usual one) then I end up with a durable reusable connector which is IMHO far superior to rubber or silicone. After several uses it will have some discoloration and I just wrapped another layer on top and in the longer run I had some cork filled PTFE stoppers with holes for grounded joints. Neat! The PTFE compresses und by pressure und heat it gets kind of sintered (PTFEs usually bad habit of giving in to "cold flow" comes out as a bonus here).

I also like the lower weight of those stoppers compared to Rubber or solid PTFE. It would be something worth to commercialize - There is a market if the price is reasonable, I am sure.

I tried a lot, this was the best.

/ORG

SuperOxide - 28-11-2021 at 07:57

Quote: Originally posted by SWIM  
Just for context, how big a flask are we talking about here?
Well, I just ordered a 4L Pyrex flask, supposedly new, from ebay (for $65 shipped! I have my suspicions - But even if its fake, it may still be useful). But in a 4L flask, I will probably never fill it past 2 or 2.5L. It accepts a #10 stopper.
Quote: Originally posted by SWIM  
Refluxing several liters of something through a little tube may lead to solvent 'spitting' out the top of your condenser, or possibly the 24/40 condenser just filling up with solvent and overflowing.

That's exactly what I was worried about. I don't think it makes sense to even try, lol.
Quote: Originally posted by SWIM  
As Belowzero said, those rubber stoppers are easy to drill out.

And, somewhat ironically, below zero is a good temperature to have your stopper at when you drill it. Leave it in the freezer overnight.

That's some great advice.

Quote: Originally posted by SWIM  
I'd try drilling one out to 7/8 inch. That ought to fit okay for a 24/40 joint. You can taper the top of the hole a bit by wrapping sandpaper around the 24/40 male joint and sticking it in there and working it around if you need to.
Start with a single hole stopper and you've got a pilot hole that'll help ensure a straight, true and centered hole.

The sandpaper around the joint is a great idea as well. I will definitely give that a shot. I just ordered these, and I may try drilling it out wider then sanding it to see if I can directly place a 24/40 in there, if not, maybe I can squeeze in a 14/20 adapter.

[Edited on 28-11-2021 by SuperOxide]

SuperOxide - 3-12-2021 at 22:20

So I got the Erlenmeyer flask in today, and the tapered collar set I already have actually works great. I didn't think it would because it just seems like it would leak. I usually use it for vacuum filtrations and the vacuum pressure makes it seal well, but it worked well here too.



I tested it with boiling 2L of water, and while that's not a big deal, I did crank the hotplate up to 300 °C right off the bat, and it held up to the immediate temperature change very well. This was a fricken steal for $65 bucks (off ebay). I recommend it to anyone that thinks they will ever need a flask this big.

macckone - 4-12-2021 at 00:52

That is a good deal on the flask.

SuperOxide - 4-12-2021 at 08:13

Quote: Originally posted by macckone  
That is a good deal on the flask.

Hell yeah it is. I was hesitant to link to it because it would feel like I was pushing it or like I was paid to say it, lol. But I think if anyone needs one, these deals would be very useful.

Im honestly kinda tempted to get a 2nd one. Not because I need it, but in case I break this one. I don't think ill ever find a deal this decent again.

[Edited on 4-12-2021 by SuperOxide]

brubei - 4-12-2021 at 13:24

I use champagne corks. Their conical or round shape makes them easy to insert or remove on a neck. You can easily make clean holes inside with a drill.

SuperOxide - 5-12-2021 at 09:05

Quote: Originally posted by brubei  
I use champagne corks. Their conical or round shape makes them easy to insert or remove on a neck. You can easily make clean holes inside with a drill.
Do they have champagne corks this large? That would be one hell of a champagne bottle, lol.

But I think the typical cork material (made from bark I believe) isn't inert enough for some things I use in the lab.

macckone - 6-12-2021 at 09:48

Superoxide,

You can buy corks pretty big and you can get cork blocks.
See the comments on covering the stopper with teflon plumbers tape.
The tape will melt at around 320C forming a solid layer, using a heat gun will prevent the cork from decomposing.

SuperOxide - 6-12-2021 at 17:34

Quote: Originally posted by macckone  
Superoxide,

You can buy corks pretty big and you can get cork blocks.
See the comments on covering the stopper with teflon plumbers tape.
The tape will melt at around 320C forming a solid layer, using a heat gun will prevent the cork from decomposing.


That's pretty interesting.

However, I think I might have found an even better solution. It occurred to me that I have a 24/40 to 45/55 adapter for my soxhlet extractor, and that #10 neck looked like it would be a close fit for it...


And, well... ill be damned. It fits pretty damn well.



Honestly, it makes a decent seal even without any grease or teflon tape, but just in case, a quick wrap or two of teflon tape and it makes a perfect seal.



It's actually very surprising how perfectly that fits, lol.

crow6283 - 6-12-2021 at 20:06

Do a quick search for a “cork borer”, this is a common tool you would see in a brick and mortar lab supply store, but if left to your own devices online maybe wouldn’t even know it exists! The common ones sold only go up to maybe 12 or 16 mm in diameter, but once you’ve got a hole that big you can use a Dremel to grind it bigger to the size you need. Alternatively, you can make your own larger sized cork borer if you have say a bit of appropriately diametered copper tube and a grinder to grind a bit of an edge on it, or you can simply heat the end up with a torch and it will melt through the rubber! I have used connections made like this (from a male ground joint, wrapped in small amount of rubber stopper stopper, to a female heavy walled flask) even for vacuum distillations (not high vacuum, just with an aspirator) in a pinch and it worked just fine, although it of course is not recommended.

-edit- should also be noted that not all rubber stoppers are created equally. The white ones used for fermenting I would not recommend for heating anything, and I’m also not sure how they would react to various organic compounds. The stoppers sold for lab use come in different colors. The green I believe are more resistant to acids and bases. Best to prepare a few for what you are doing and toss them after a while, after repeated use and exposure they have a tendency to harden and crack.

[Edited on 7-12-2021 by crow6283]

macckone - 9-12-2021 at 10:46

Given that it is tapered and the neck is not, as long as the big end is bigger and the small end is smaller on the tapered piece, it should fit pretty well if the neck is round. If it isn't round just add more teflon tape on that side.

SuperOxide - 10-12-2021 at 09:11

Quote: Originally posted by macckone  
Given that it is tapered and the neck is not, as long as the big end is bigger and the small end is smaller on the tapered piece, it should fit pretty well if the neck is round. If it isn't round just add more teflon tape on that side.

It does fit, almost like it was meant to fit there. Damn near perfect, lol. I recon I could even get it to form a seal with just some grease, but I'll use a layer (or two) of teflon tape instead, just to be safe.

violet sin - 10-12-2021 at 19:29

@ crow6283
I agree. You can certainly sharpen the OD of a piece of copper tube by relieving it of the ID edge with a file. It can then be stuck in a drill press or hand drill to make holes in thing that don't like to cut nicely.

I've used it on cork and solid silicone caulk. If you've ever had a tube that was found to be old and solid... Free the slug of solid material, cut to length and bore out.

It doesn't do much at first but the friction builds and it will suddenly sink in the surface and then slowly progress further. I've not made them bigger than half inch, but larger pipe could be used on a smaller shaft to fit the motored device what ever it be.

You don't have to run out any buy everything if you've some tools and an hour or so free time. I'm good at building things so that helps. Only way to get better is keep building, so level up.

Edit: I butchered your screen name, then fixed it, sorry.

[Edited on 11-12-2021 by violet sin]

SWIM - 11-12-2021 at 11:31

That does look like a good fit.
Good thing you bought a Quality flask.

Some cheap modern Erlenmeyers can be lumpy or out of round at the top, but major manufacturers usually have nice even beads on their flasks.

Given the option I'll go for used equipment from a major manufacturer before new stuff from somebody I've never heard of for just this reason.

[Edited on 11-12-2021 by SWIM]

SuperOxide - 11-12-2021 at 13:30

Quote: Originally posted by SWIM  
Given the option I'll go for used equipment from a major manufacturer before new stuff from somebody I've never heard of for just this reason.

I couldn't agree more. All my favorite glassware is the used stuff from Ebay (Mostly from BiotectCT or BiotectCA, amazing prices). I get all the best brands for very affordable prices.
I wish I realized this earlier, lol. I have so many crappy pieces of glassware that I don't use because of how bad quality they are (eg: super thin walls or bad fitting joints).

Fyndium - 13-12-2021 at 08:01

I have a couple of ground joints that are slightly asymmetric and leak under vacuum. A noticeable bubble trail can be observed when applying. I decommissioned these joints, one which was thermowell, not only because they leaked, although a powerful pump could overrun the leak easily, but because they can cause uneven stress distribution to glass, which can be catastrophic danger in vacuum work.

SuperOxide - 1-1-2022 at 08:19

Quote: Originally posted by Fyndium  
I have a couple of ground joints that are slightly asymmetric and leak under vacuum. A noticeable bubble trail can be observed when applying. I decommissioned these joints, one which was thermowell, not only because they leaked, although a powerful pump could overrun the leak easily, but because they can cause uneven stress distribution to glass, which can be catastrophic danger in vacuum work.

Wouldn't some vacuum grease work? I definitely have some joints that leak, but a gob or two of dow-corning vacuum grease seems to help.

By the way, if you buy dow-corning vacuum grease off ebay, be prepared to get a tube of dupont grease. I guess its the same thing, but caught me off guard. lol.