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wireshark
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Another vote for vaseline
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quantumcorespacealchemyst
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teflon sheeting
i have been using teflon sheets from ebay and cutting them to double wrap around the joints. i have used them for diethyl ether and chloroform as well
as boiling over nitric acid and fuming iodine. the times where i use the solvents, there is liquid that surrounds the joint and there is bubbling,
although it seems to condense and not leave the joint, at least not much if it does. the smell is not strong exept for around the output of the
condensor. i have been wary of the temperature though with say the diethyl ether.
i can't guarantee no leakage and you will have to try it to see what i mean with say chloroform or something. although the joints seem to wet fully,
they don't seem to leak.
i usually wrap the sheet around the male joint and get an idea of an alright strip and use an exacto knife to trace around part, getting a rough idea,
unwrapping, cutting the rest and then refining it on the male joint. using a compass and drawing out the arc can make a good template for making many
economically after hacking at it. i have done this for the 14/20 and don't have paper or compass wide enough for the other ones currently.
hope this helps
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subsecret
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I use Teflon tape for my joints, and it seems to work well. Keck clips can be a problem, because the thin layer of tape expands the joint slightly. I
used to use vaseline, but this was hard to wash off, and as stated, not very inert.
I avoid using vacuum grease because I don't want to put in the extra time to clean the joint after each use. Washing with soap and a distilled water
rinse is the usual treatment for my glassware. How do you more experienced members get that Corning grease off your glassware?
Fear is what you get when caution wasn't enough.
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quantumcorespacealchemyst
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Ethyl Acetate, link and mention at bottom
yea, i have been using extra clamps to secure the apparatuses in place i dont have keck clips and have realized they may not fit. i am not that
experienced or have used corning grease and will say also that for non heavy cleanup, BORAX has worked great for me, and letting flasks and stuff soak
in a bucket of it for a week or so had dislodged some organic gunk that came with my flasks (i made pirahna solution and then realized that the H2O2
bleach was 3-5% not 30%, which explained the black dots not dissolving, so i just dumped it in my wash bucket and forgot about it for a while and it
wiped off easy when i picked it out again). i guess washing soda would have done the same and there may even have been a tiny bit of it in the water
too, although i find when washing and rinsing glassware the BORAX has just the right bit of something, i don't know and the tiny bits of it that don't
dissolve work good for abrasion and it doesn't hurt/burn and rinses off smoothly.
cleaning the the greases though, i have no clue about.
edit: these people have some methods.
the person rrkss says " Was able to clean my joints to a nice frosty color in a matter of seconds using Ethyl Acetate" and that it is a cheap and
simple solvent
http://www.sciencemadness.org/talk/viewthread.php?tid=14023
[Edited on 4-12-2014 by quantumcorespacealchemyst]
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forgottenpassword
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For every day use (non-vacuum applications) I too am a big fan of vaseline. It works: it provides thermal contact between the two pieces of glassware,
and it prevents the joints from freezing. Any that manages to contaminate your product is easily removed by washing with petroleum ether. The same can
NOT be said of high-vacuum grease. It is essentially insoluble in anything and you will have have to re-chromatograph or re-distil your product if it
becomes contaminated with it. Having said that, used-properly, there should be no risk of contamination whatsoever. Teflon tape I've never tried,
although it does sound like an excellent and clean general method. But I'm rather fond of greasing joints the old-fashioned way, and see no reason to
change.
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j_sum1
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I would think that teflon will prevent heat conduction at the joint. I am by no means an expert here but if you were expecting a reasonable amount of
thermal stress then you might want to rethink teflon tape -- even if it does provide a bit of extra give at the join.
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forgottenpassword
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Good point, that. Certainly there will be more stress on the glass due to different expansion rates; although borosilicate is quite superb in that
department, so whether it makes any practical difference I don't know. Teflon does soften somewhat with heat. In fact it is quite 'soft' even when
cold: as plumber's tape, anyway: so maybe it provides SOME thermal contact.
[Edited on 4-12-2014 by forgottenpassword]
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Mailinmypocket
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As mentioned above by Arthur Dent, dielectric silicone grease is the way to go. A tube lasts for ever and the stuff is surprisingly similar to the
real stuff! Home Depot has one that also mentions vacuum uses:
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forgottenpassword
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Which is, what, half the price of Dow Corning high vacuum grease? The last tube I bought was 50g for £10. Is it really worth the saving? Would you
use that on a high vacuum line?
[Edited on 4-12-2014 by forgottenpassword]
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Mailinmypocket
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It's not so much the fact that it's cheaper but rather much more accessible. I've only seen the Corning stuff at higher prices than that (then again I
haven't spent much time searching for a deal on the stuff). Not entirely sure what the vacuum part is about though and So I have no clue how it would
perform on high vac lines...
It beats the heck out of Vaseline on joints IMO
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careysub
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I don't think any joint dressing that works will prevent heat conduction. It is simply too thin to have a substantial effect.
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lysander
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I thought teflon (tape or plumber's paste) was unbeatable: Unless you're working with fluorines PTFE doesn't react with anything. Isn't silicone
grease a little more reactive?
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Deathunter88
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Another vote for not using grease. I have distilled ethanol, ether, sulphuric acid, acetone and many many more without a single drop of grease. And
for all of them I got very very close to 100% yield based on starting liquid. Not once have I suffered a frozen joint.
The only time I have used grease (sulphuric acid) actually is when distilling bromine, and even then I felt that the "grease" was unnecessary.
Take my advice with a grain of salt, as it probably depends on the quality of your ground glass joints. I buy from (what I think) is the best
manufacturer in China and their stuff is really top notch.
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subsecret
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I use plumbers' grease or PTFE tape for my joints, but in the case of bromine or nitric acid, I use sulfuric acid. It may be worth it to buy a tube of
high vacuum grease and distribute it to members who need small amounts of it.
Fear is what you get when caution wasn't enough.
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j_sum1
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I bought this
I figured that it would last almost indefinitely and I may as well have something that would work consistently well whatever the application. It
didn't seem like a huge expense to me.
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NedsHead
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I bought my distillation kit from sciencesupply.com.au and highly recommend them but that is a lot of money for 50g of vac grease, I found a much
better deal a few days ago http://www.ebay.com.au/itm/291406381912?_trksid=p2060353.m14...
edit: I just noticed they are the same grease!
[Edited on 16-9-2015 by NedsHead]
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j_sum1
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I don't think I paid that much.
From memory it was $15 AU.
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NedsHead
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he has some good deals occasionally, you must have caught him at the right time. sometimes his prices are on par with the Chinese prices but without
the loooong wait
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macckone
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United glass tech sells teflon seals.
Most lab supply places sell silicone grease.
Auto parts places have a variety of grease compounds.
For less sensitive reactions Vaseline works well.
Sulfuric acid is a standby for certain reactions.
Ptfe plumbers tape is also great.
And don't forget polyimide tape.
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