Sciencemadness Discussion Board

Condenser without ground glass joints

Sniffity - 19-5-2015 at 10:18

So.. I recently got (as a gift) a Graham Condemser w/o ground glass joints. Which got me thinking: Is there any reason why joints shouldn't be made out of ground glass? Can I actually use this condenser for anything serious? D:

I'd love using it, but would rather avoid accidents/failures if any are bound to occur. Thanks in advance.

DraconicAcid - 19-5-2015 at 10:30

I have a condensor that pokes through a stopper. It works fine, as long as you're not using a solvent that will attack rubber.

Bot0nist - 19-5-2015 at 11:00

Ground glass joints are preferable, due to their versatility and ability to withstand caustic and corrosive distillates (nitric and hydrochloric acids, for example) and high temperatures. What do you intend to distill? The stoppers you are able use will limit what you can use your condenser for.

[Edited on 19-5-2015 by Bot0nist]

Chemosynthesis - 19-5-2015 at 11:23

I have a bunch of old condensers with detachable jackets held on by bored out rubber stoppers and lacking ground joints. I prefer using my ground glassware as it is far superior, but these provide very convenient air condensers when disassembled and are easy to clean when using thick coolants. They are largely relics from days when ground glass was a bit of a luxury, from my understanding. They were also basically free.

As long as you are careful with temperatures and chemical reactivity, and/or select your stopper material well, there is no reason these can't serve for a great deal of reactions or purifications. Since yours is a Graham, you are probably using this in a downward distillation, and you may get away with separating this from your heated flask enough to minimize heat exposure to the stoppers. Your application will dictate stopper material, from butyl rubbers to silicone to PTFE. For chemical reactivity, you may be able to entirely replace or wrap parts of incompatable stoppers with PTFE tape or something if you find yourself pressed for resources.

One thing to look out for is that rubber stoppers can get very stuck or even break glass if used under vacuum, and I recommend disassembling after use in most cases, as with ground glass, since sometimes rubber can stick to your glassware with age. I just pulled such a condenser out recently and had to separate the rubber seals with grease on a toothpick, rotating between the glass and rubber, to remove.

[Edited on 19-5-2015 by Chemosynthesis]

aga - 19-5-2015 at 11:43

Cork and Rubber work amazingly well, and will happily seal your non-quickfit glassware.

The only thing to remember is that the rubber/cork won't last forever, and so you need to check them before/after use.

If you're doing experiments where your life depends on the Seals holding up, well, i'd pick other experiments if i were you, whether you have ground glass joints or not.