The Vespiary
The Hive => Newbee Forum => Topic started by: abuse on November 29, 2003, 09:24:00 PM
-
I searched on TFSE and found scattered info on this, but I was only able to find a single post where a Bee mentioned to use a #4 rubber stopper on a 24/40 joint for the purposes of making a sep funnel into an addition funnel. Anyway, is #4 the correct size? Will that size fit well into, say, a 2000ml flask with 24/40 joints? I found information elsewhere (not the Hive) where they claimed that #5 stopper will fit 24/40, so I'm a bit confused.
-
#4 fits a 24/40 joint very well, #5 will sit ontop, also fitting it less well.
My suggestion to you is to buy ground glass jointed _everything_, really, it will make your life easier than trying to use rubber stoppers. (the only thing I do not recommend buying GG joints for is the thermometer... but do buy the 10/30 female joint connections... but when it comes to the actual thermometer, just use some teflon tape to get a regular thermometer to make a perfect seal--this is because, IMHO, O-rings suck and GG thermometers are too expensive)
-
You can obtain a 'thermometer adaptor' which is a ground glass connector with a piece of rubber on the top. Usually you will need to use some teflon tape to secure the thermometer in the correct place for distillation (e.g. correct height but also -not- touching any of the glass surfaces of the distillation apparatus).
As per the original question, there are also plastic stoppers available which are designed to fit standard taper ground glass joints (teflon or hdpe I can't remember) which are generally cheaper than the glass counterpart and as a plus are easily drilled through.
adam
-
Chromic: What do you think of the rubber-topped thermometer adapter?
-
That is the O-ring thermometer adapter he is talking about.
-
Aren't there at least three types of thermometer adapters: all glass, glass with a screw cap/o-ring, and glass with a rubber top?
-
First off, for future reference, rubber stopper sizes are usually explained enough in detail in the on-line or paper catalogs of most small lab suppliers to determine which you would need.
As far as thermo. adapters: never use any but rubber/glass comb. in my opinion. Glass thermometer in a glass ground joint is just asking for trouble: how will you get an airtight seal without risking breakage. O-ring aparatuses should be abandoned altogether. I don't know why any1 here would use o-rings. See Zubrick for details if you don't understand or try using them.
-
the big orange hardware store(s) care the black rubber stoppers your looking for.
-
Yeah, there are three types of adapters. I really dislike the all rubber variety, even more so than the screw top with the O-ring. Try the teflon tape idea, it produces a great seal and won't stick as is possible with a ground glass thermometer.
-
I use the o-ring + screw caps exclusively, my distillation adaptors have the threaded glass heads at the top and I also have some ground glass peices with the threaded heads to put in the necks of flasks. I never have had a problem using these under vaccuum... I just keep losing o-rings!
blaaky
-
You can pick up lots of o-rings at your local hardware store for replacement. Honestly though, once you try the 10/30 thermo heads and teflon tape on your thermometers, you won't want to go back to the o-rings or all rubber variety.
I've never had many problems with the o-ring adapters, I have had the plastic on the screw cap break before (I think it was some nitric oxides that slowly led to the plastic cracking) and the rubber rings will degrade over time too... but they're, generally speaking, quite reliable. STILL... you've better off with the solution I mentioned.