Lambda-Eyde - 30-1-2012 at 16:24
I'm looking for a compability chart of some sort which lists the resistance of silicone rubber to diethyl ether. I tried googling, but all the charts
I found were unsatisfactory. Maybe my search-fu is weak.
I want to purchase silicone septa and GL45 screw caps (Carl Roth #LL52.1 and L994.1 respectively) to go with my reagent bottles, in order to store dry
ether for a prolonged period, so the septas (septa? septums? argh.) would have to resist ether vapours for several months. Or, is it so that trying to
store dry ether and keeping it dry is futile? Carl Roth doesn't stock PTFE-coated silicone septa, only the pure silicone ones. I'd rather not buy from
another supplier.
Also, I'd like to link you to the products, but the imbecile who wrote the code for the page somehow came up with the idea of implementing some sort
of time-out mechanism, so there are no permanent links to their product pages. If I leave the page for 30 minutes and click a link after that time, I
get a damn error message. 
Sort of off-topic, but if any coders out there can
provide some sort of reasoning/motivation behind this horribly annoying piece of code, then maybe I could sleep tonight.
Thanks.
Magpie - 30-1-2012 at 16:44
http://www.coleparmer.com/Chemical-Resistance
Lambda-Eyde - 30-1-2012 at 16:57
Ah, thank you. I can't believe I didn't check out that site. It's even in my bookmarks, but I forgot to look there after giving up Google...
Anyways, silicone + ether gives a rating of "D - Severe Effect, not recommended for ANY use" 
Looks like I'll have to hunt down some PTFE coated ones. Ace Glass has some for a very friendly price. I've registered on their site and
I'm waiting to hear back from them. A bag of 10 should fit in an envelope, so shipping from the US wouldn't be too much of a (financial) hassle. 
If anyone has other suggestions on where to get silicone/PTFE septa for GL32/GL45 caps I'd be glad to hear them.
bahamuth - 31-1-2012 at 02:50
GL45 Red Caps for use with Schott Duran ISO Bottles NEW
There you got lined caps, either drill a hole through the cap or pry out the liner.
Magpie - 31-1-2012 at 09:10
I have been buying 125 mL bottles with ptfe lined caps from Qorpak for storage of ether, absolute alcohol, etc. But I find that the ptfe liner takes
a set where it contacts the bottle rim. These Schott Duran caps with the rubber/ptfe liner look like they would provide a better seal.
Does anyone know if there is an equivalent cap readily available in the US?
Lambda-Eyde - 31-1-2012 at 10:53
I'm not sure if you understand what I want. I'm after one of these caps (which I have no problem getting):
What I'm after is a septum to go with it - I want to keep my dry ether and other solvents in bottles with these caps so I can transfer it by
cannula/syringe. So it's septa I want, not PTFE/silicone liners. I have plenty of red and blue GL45 caps already, together with around 15 GL45 threaded bottles.
Magpie: Duran isn't the only ones producing these bottles. I bought 10 500 mL Simax bottles with blue GL45 caps for about 30$. Fisher Scientific also
makes similar bottles, and as I mentioned, Ace Glass carries a wide range of GL45 caps, liners and septa to go with them. These bottles normally come
with blue PP caps without liners which are fine for most inorganics and some organics. If you want to store things like bromine, fuming nitric acid
and powerful solvents you'll need the red PTFE lined ones. I store my bromine in a 100 ml bottle with such a cap, and it hasn't deteriorated for
almost two years.
Dr.Bob - 31-1-2012 at 11:04
I can tell you from experience that once you puncture a silicone or rubber septa, with or without a teflon backing, that your low boiling solvents
will evaporate quickly, and also get exposed to air. I actually did a study to test that with DCM, for my previous job, as we had air-sensitive
solutions we were trying to dispense with automation to 96 well plates. It was a tough challenge, and the septa often failed once punctured.
I will note that Acros uses a system like this for their anhydrous solvents, and it is OK, but the septa start leaking quickly, and you have to
parafilm them to keep out water, and even that does not do well. Aldrich has their septa seal bottles, which are as bad or worse for the long term.
Most septa that were not punctured would hold up pretty well to non-chlorinated solvents (ether, THF, alcohols), but DCM would diffuse enough to start
softening the rubber (silicone, butyl, or nitrile) within a week or two. Viton lasted a little longer. But once there was a puncture in a (Sure
seal type) bottle cap septa, they would suffer from evaporation quickly (>1% wt loss per week). (Note, thicker 24/40 type septa DO better).
Even Viton did poorly with DCM after puncturing.
The only material we found which resisted evaporation after puncturing was a Goretex experimental fluoroelasomer which cost $$$ and was only barely
available then. (See http://www.gore.com/en_xx/products/pumpcomponents/products/s... for one example of the polymer in tubing. ) That stuff was incredible, you could
soak it in any almost any chemical including TFA and DCM mixed and it would not swell, soften, or harden. And it resealed incredibly well. But it
cost a fortune.
I would suggest that you store ether in a screw top amber bottle with a Teflon faced cap, and then try to blow nitrogen over it after use and recap
it. Or use a thicker septa and blow nitrogen in while removing ether, if you want to keep it anhydrous. The 125 ml bottles from Quarpak are good for
that. I don't know that the Duran bottles would do better, based on my usage. The seals are not as perfect as they appear.
Lambda-Eyde - 31-1-2012 at 11:25
Thanks for sharing your experiences, Dr. Bob. I feared that would be the case. The septa I'm looking at are 3 mm thick, though - I don't know how
thick yours were, but I can't imagine the ones I'm looking at would leak as easily?
The ideal solution would be to have a cap on top of the septum, something like the Aldrich sure-seal bottles, only with larger, better septa - and a
way to keep it reusable. The sure-seal bottles use a beer bottle-styled cap under the screw cap - I'd like some sort of system where I could change
the septa as they get worn and open up the whole bottle by just taking off the septum or unscrewing a(nother) cap.
I might also add that buying dry ether in septum bottles from Acros is out of the question. I can buy from Acros, but the prices are perverse and I'd
also like to dry, distill and bottle my own dry ether.
Dr.Bob - 31-1-2012 at 12:47
The bottles that E-Merck use has a septa with screw on top above it. If their septa were better quality, the idea would be great. But they use a
huge, thin, septa with a small access hole to it, which gives the worse leakage and least convenient usage of any of the systems used.
The thicker the septa the better, and the smaller the needle, the better. For solvents, I try to use the smallest practical needle. For many
reagents, too small of a needle will clog (eg, butyl lithium, LAH soln, etc) but with clean solvents, I would rather use a small one and not make a
giant hole in the septa. That does make it seal much better and longer. For really good storage, a glass sealed bottle with a septa and stopcock
are really good.
See Figure 15 below for the best solution I have seen, we used to use these stopcock topped bottles for nBuLi solutions and similar reagents, which
would keep a good titer for months in these bottles.
http://www.purdue.edu/rem/hmm/al_techbull_al134.pdf