Sciencemadness Discussion Board

glass joint sealer?

GreenD - 29-5-2011 at 11:29

This is dumb - the stuff is probably cheap, but would vaseline be OK to use for a sealant for vacuum or even regular distillation of glass joints? Anyone use something else OTC? Hair gel? haha

piracetam - 29-5-2011 at 11:47

I've used vaseline, and thought it sufficed.
silicone grease has higher viscosity though, probably provides a better seal.

hkparker - 29-5-2011 at 11:58

I've only ever used vasoline and it has worked great for me, though I'm sure there are better materials to use.

piracetam - 29-5-2011 at 12:03

back in the day, they used to just melt rubberbands in vaseline, and use that

Arthur Dent - 30-5-2011 at 05:07

Check out this thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=15156&...

...where I've been discussing about Vacuum Grease. The expensive stuff is way too expensive, but I have found an excellent and very inexpensive substitute.

Go to an automotive parts shop like Canadian Tire or Napa and get the electrical contact silicon grease, the stuff they use to protect car connectors and contacts from moisture. It's about 8 to 10$ per tube and it's EXACTLY the same stuff as the ultra expensive Beckmans grease.

I strongly suggest avoiding vaseline, it's not as chemically inert as silicon grease plus it doesn't withstand as much heat, so it could literally melt off the glass joints, contaminate your solution and let air in or let gas out, which would defeat the purpose of a glass joint. The silicon grease is inexpensive and withstands strong heat and is nearly chemically inert, and you only need a small dab, which you spread around the joint.

Robert


[Edited on 30-5-2011 by Arthur Dent]

hissingnoise - 30-5-2011 at 06:01

Teflon tape for plumbers works well as long as it's evenly applied, but I wouldn't trust it for use with an anyway high vacuum!
If I were doing a vac distillation I'd want two or three Glindemann rings on the cones . . .
The pressure between cone and socket causes some flow in the teflon ring so that intimate contact is absolutely assured.
And it's mess-free . . .



digitalemu - 30-5-2011 at 09:25

Electrical contact silicon grease for the ground glass then taping up the outside of joints with Teflon tape, then keck clamp on the Teflon tape for extra security works great. Vaseline is a bit too runny especially when there is any heat involved.

The WiZard is In - 30-5-2011 at 09:43

Quote: Originally posted by GreenD  
This is dumb - the stuff is probably cheap, but would vaseline be OK to use for a sealant for vacuum or even regular distillation of glass joints? Anyone use something else OTC? Hair gel? haha

Vaseline ® sucks - literally. I used it on a large all glass desiccator
that I did't have occasion to use until years latter. Getting la
lid off was a pain. The petroleum jelly had dried/hardened. I
put it under hot water to soften it - increase interior pressure.

I like the silicon wire protector idea. Don't get it on your hands
it is hard to get off. I remember years ago -- after using silicon
caulking --- jump into my pickup truck ---- what da! My hand's
were so slippery I could not hold on too the steering wheel.


djh
----
His talk was like a stream, which runs
With rapid change from rocks to roses;
It slipped from politics to puns,
It passes from Mahomet to Moses;
Beginning with the laws which keep
The Planets in their radian courses;
And ending with some precept deep
For dressing eels, or shoeing horses.
Winthrop Mackworth Praed
The Vicar

GreenD - 30-5-2011 at 10:00

any brand names associated with the stuff at the automotive place? People might not even know what I'm talking about if I ask for that... but I'll definitely give it a shot. Thanks ya'llz

hissingnoise - 30-5-2011 at 10:30

Quote:
Electrical contact silicon grease for the ground glass then taping up the outside of joints with Teflon tape, then keck clamp on the Teflon tape for extra security works great.

You don't have to be a plumber to be able to effect a good seal with teflon tape and for normal distillation, it replaces vaseline and silicone greases.
As I said already, Glindemann rings flow under pressure into the minute pitting of the ground surfaces . . .
This property makes them ideal for vacuum work but they are not used singly!
I remember vaseline as a yellowing bubbling liquid, with NO<sub>2</sub> occasionally visibly leaking from joints . . .


hissingnoise - 30-5-2011 at 12:22

BTW, Dr Glindemann is quite a character . . .

peach - 30-5-2011 at 13:36

I'd go with the teflon tape if you can't find some sort of cheap silicone grease.

I used to use vaseline and only vasline when I first got bits of taper glassware; because I could barely afford the glass let alone special grease and everything else for it. It's not ideal, but it does work. It can be washed out of joints quite rapidly by solvents as they go by and it is chemically reactive to a degree. But it may not actually be that much of an issue for you, particularly at first where you'll be learning a lot just using the glassware and getting used to it.

One thing is for sure, it's certainly better than putting the glass together with nothing between the joints - they're not only going to piss condensates and bleed air & reactive gases, they'll end up seized (perhaps permanently).

I'm sure I have seen something very similar to those taper bands used by girls in their hair, called 'invisible hair bands' or 'no slip'. They of coarse are unlikely to be teflon, but then, neither are the Suba Seals used on air free systems that cost thousands of dollars and that are in contact with warm solvents for days. The Suba Seals are natural rubber (elastic bands) or silicone. And I expect some of the hair bands are silicone as well, as they feel slippery and smooth and don't catch on hair (anyone NOT tried putting an elastic band on their head and experienced what it's like pulling it off?).

These are the ones, and I think they may be silicone.


Also available in sea horse, penguin, fish, sea lion, dolphin and shark taper configurations from all 6 years' old clothing outlets. These are silicone.


[Edited on 30-5-2011 by peach]

piracetam - 30-5-2011 at 14:53

tbh, I'm not sure if silicone grease gets in the rxn mixture
I recently did a MALDI characterization of an extract (which also had tween 80 in it), and got a pattern for ethylene glycol

halogenated hydrocarbons may somewhat dissolve the silicone grease.

Arthur Dent - 30-5-2011 at 15:31

Quote: Originally posted by piracetam  

halogenated hydrocarbons may somewhat dissolve the silicone grease.


I tried and definitely no it will not, the automotive silicon grease is totally imprevious to all of the solvents I tried, including trichloroethane and also to very strong mineral acids. Here's a picture of the grease I use, and it's available at any suto parts store under "silicone dielectric compound"



Robert

piracetam - 30-5-2011 at 19:47

have you ever analyzed it?
I'll have to add some to dcm agan, then spot it on a plate, to rule it out.

MS doesn't lie. it's sensitive enough to detect trace amounts, pg/mL
it's even shown leachates from PP microcentrifuge tubes exposed to dcm.

[Edited on 31-5-2011 by piracetam]

Arthur Dent - 31-5-2011 at 03:58

I have tried about 6 solvents that I have, and the major concentrated acids and acid mixtures and that's plenty for me. I don't have DCM but if the grease is not affected by chloroform, trichloroethane nor acetone, it's a good start.

Besides, if I ever work in analytical chemistry where ppb contamination would affect a reaction, i'll use the grease at the right. But I'm sure any member on this board working in this field already has all the adequate glassware and professional vacuum grease. What we're talking here is an inexpensive alternative to the "professional vacuum grease". This compound is inexpensive and is in every point similar to the real stuff. And so far, it's done a top notch job with my distillation glassware and my glass dessicator. I'm sure it will be more than adequate with 99% of the experiments performed on our board.

Another good test (that I can't perform because I don't have any) would be to fill a 24/40 flask with bromine, and dab a 24/40 glass stopper with the grease and see how long it will take for the bromine to "creep up" the joint. This would be a definitive test to see if there's any difference between the two. perhaps I could try this with iodine crystals?

Robert

#maverick# - 8-6-2011 at 17:01

i found some lithium grease in my shed main ingredient is perchloroethylene i wondering how would this work as a glass joint sealer

#maverick# - 8-6-2011 at 17:12

edit upon further research it is not a suitable grease as it is not chemically inert, i will stop being a cheap bastardd and buy some dielectric grease

BromicAcid - 8-6-2011 at 19:39

Personally I love Glindemann rings, and you can reuse them too. They give a surprisingly good seal. I've used sulfuric acid a few times in place of vacuum grease, works good for distillations for, of all things, sulfuric acid ;) not to mention perchloric acid. I've also used sodium silicate for that permanent (sounds good at the time but I'm gonna regret it later) seal. At work we use the Dow High Vacuum grease. It holds up pretty good but will leach out of the joint upon prolonged refluxing of solvents like toluene and of course things like DAST just consume it wholesale.