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Biochemscientist
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Grease sources for glassware joints?
Hi all,
I recently obtained my first distillation set and will soon be embarking on a few distillation projects. I am new to working with this type of
glassware, and I one thing I am wondering is about greasing the joints. Is greasing required, or is it optional? Are there any readily-available
substances that will function for this purpose such as glycerin or petroleum jelly, or is it necessary to order a special type of grease?
Thanks!
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hkparker
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required! Don't do what I did when I got my first ground glass joint and just put them together, they can easily be stuck without lubrication.
I have always used vasaline (petroleum jelly) and it works great. I would not use glycerin. Other substances such as silicon oil or teflon tape are
sometimes used but for most everything petroleum jelly does great.
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Bot0nist
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Also, look for plumbers silicon grease. It is very unreactive and a lot cheaper than buying 'vacuum grease.'
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Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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woelen
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Another important thing is to use a VERY thin layer of grease. Keep in mind that the grease may dissolve in some compounds and may contaminate what
you are distilling.
I do not always grease the joints. Sometimes the compound to be distilled is a perfect agent for sealing the joints. In such cases I take some of the
liquid to be distilled and _slightly_ wet the joints with that.
In some special cases I use concentrated sulphuric acid for greasing. E.g. when I distill bromine or fuming nitric acid I do that. The concentrated
sulphuric acid does not dissolve in bromine and it does not react with bromine, while most greases both dissolve and react. It does dissolve in fuming
nitric acid and in that case the greasing must be particularly thin.
When I distill organic water-insoluble solvents (e.g. hexane), then I use water for 'greasing' the joints.
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Arthur Dent
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There have been many threads on this... again, i'll mention one particular type of grease that I have discovered is narly as good as the real stuff:
Left ot the picture above is automotive silicone dielectric compound. It's about $7 or $8 a tube, on the right is the "real thing" that's about $50
for one ounce!!!
Both are nearly similar in every point, chemically unreactive to nearly everything, and unless you do some hi-end analytical chemistry, will be
perfectly suited for all ground glass joints.
The problem with vaseline is that it doesn't stand up very well to heat, kind of runs off, possibly contaminating the solution you want to isolate,
and it reacts with certain hydrocarbons, effectively f***ing up your reactions in certain cases. And unless you have absolutely perfect-fitting
joints, Silicon oil will not be adequate. Teflon tape is very good, but unless you tape the joint perfectly without the slightest crease in the tape,
it won't be a good sealed joint.
That automotive silicone dielectric compound pictured above can be found at any Canadian Tire, or any automotive parts store like NAPA and places of
that sort.
Robert
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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fledarmus
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For whatever grease you are using, the key is to use as little as you need to avoid contaminating your reaction and everything else your glassware
touches. When I use grease at all (which is very rarely), I apply a small amount to the top half of the inner joint and wipe it off with a paper
towel, then put the joint together. The joint will appear white when it is put together completely dry, and will appear clear where there is a film of
grease. You want a complete clear ring in the top half of the joint, and at least a complete dry ring at the very bottom of the joint. Otherwise you
will be getting grease into your reaction.
Usually I only grease joints that will be subjected either to vacuum, long periods (several days) of reflux, or strong bases. So little grease is
required that it is worth spending the money on a high-quality silicon high vacuum grease - it will take you a long time to use up one tube. I've
never seen anything as expensive as $50 an ounce - even from a high end chemical supply house like Aldrich it's only about $6 an ounce. This is what I
use: Vacuum grease
Vaseline is very soluble in most non-polar solvents like toluene and hexane, and tends to get into everything. Silicon oil is too thin and tends to
run out of the joint.
**Edited to add this exception based on Arthur Dent's picture - I use much more vacuum grease to seal things like desicators and vacuum ovens than I
use on reaction glassware. These are not coming into contact with solvents so they will not contaminate your reaction unless you touch them, and since
the joints remain in contact for very long periods of time under vacuum, they do tend to freeze up if they are not used regularly and occasionally
cleaned and regreased. Solvent stills, which also run constantly for long periods of time, are so hard to keep joints free that we've found it worth
the money to add teflon sleeves (SciMar teflon sleeve) to each of the joints. Saves us a lot of broken glassware when we do eventually need to clean out the stills.
[Edited on 19-8-2011 by fledarmus]
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Bot0nist
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Quote: Originally posted by woelen  |
In some special cases I use concentrated sulphuric acid for greasing. E.g. when I distill bromine or fuming nitric acid I do that. The concentrated
sulphuric acid does not dissolve in bromine and it does not react with bromine, while most greases both dissolve and react. It does dissolve in fuming
nitric acid and in that case the greasing must be particularly thin.
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Wow, I never thought of using H<sub>2</sub>SO<sub>4</sub> to lube my joints in my HNO<sub>3</sub> distillation. It
makes perfect sense though. It's slightly viscous, and for my needs a little sulfuric acid contamination is not a problem. I'll be trying it this
weekend. Thank you woelen!
[Edited on 19-8-2011 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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redox
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I would recommend just buying regular vacuum grease. About 5 months ago I bought 1/4 of an ounce of high-vacuum grease on ebay for $12, and I have
barely broken the surface! Keep in mind that I have used this frequently. A little bit of grease goes a long, long, way.
Also, it probably matters that I only use 14/20 and 14/10 joints, which are significantly smaller than 24/40.
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User
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I also would recommend using the real stuff, its very inert,at least when this is requires.
On any other occasion ,for example when distilling alcohol just use petroleum jelly.
It depends heavily on the application.
What a fine day for chemistry this is.
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MeSynth
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I'm sure that as long as you never apply a vacuum and you dont push them together harder than you need to in order to get the clip on you dont need
lube for the joints.
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Mildronate
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I use vaseline or nothing.
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magnus454
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Plumbers waterproof grease (HOME DEPOT) or REESE trailer ball hitch lubricant (TEFLON) found at many autopart stores, and outdoor sports stores
History is repeating itself.
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User
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| Quote: |
I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need
lube for the joints. |
Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.
What a fine day for chemistry this is.
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MeSynth
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| Quote: Originally posted by User |
| Quote: |
I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need
lube for the joints. |
Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.
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As long as your set up isn't closed (why?) then it shouldn't have the pressure needed to escape through the joints. The flow of gas/pressure will flow
out of the set up just like it would with the joints greased unless your glassware is no good or the joints have been damaged. Plus! Say your
distilling your "volatile liquid" and you just greased your joints. That gas is going to touch the grease and possibly react with it and possibly
contaminate what ever it is your distilling.
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hkparker
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| Quote: Originally posted by MeSynth | | I'm sure that as long as you never apply a vacuum and you dont push them together harder than you need to in order to get the clip on you dont need
lube for the joints. |
The fact that joins can become welded together means you need lube. Otherwise it is likely that they will get stuck, even if you don't push them
together very hard.
But as woelen said, many different compounds can be used as lube depending on what your distilling as to reduce contamination.
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"Nothing is too wonderful to be true if it be consistent with the laws of nature." -Michael Faraday
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Bot0nist
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| Quote: Originally posted by MeSynth | | Quote: Originally posted by User |
| Quote: |
I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need
lube for the joints. |
Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.
|
As long as your set up isn't closed (why?) then it shouldn't have the pressure needed to escape through the joints. The flow of gas/pressure will flow
out of the set up just like it would with the joints greased unless your glassware is no good or the joints have been damaged. Plus! Say your
distilling your "volatile liquid" and you just greased your joints. That gas is going to touch the grease and possibly react with it and possibly
contaminate what ever it is your distilling. |
It is very unlikely to react with silicone grease.
Volatile liquids do bleed out the joints. Just the other day I was drying some solvents and the methyl ethyl ketone was seeping out of one of joints,
even though I greased it. Stinky stuff.
[Edited on 21-8-2011 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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redox
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| Quote: Originally posted by Bot0nist | | Quote: Originally posted by MeSynth | | Quote: Originally posted by User |
| Quote: |
I'm sure that as long as you never apply a vacuum and you don't push them together harder than you need to in order to get the clip on you don't need
lube for the joints. |
Not entirely true, when one distills highly volatile liquids the joints start to bleed, seen this happen on multiple occasions.
|
As long as your set up isn't closed (why?) then it shouldn't have the pressure needed to escape through the joints. The flow of gas/pressure will flow
out of the set up just like it would with the joints greased unless your glassware is no good or the joints have been damaged. Plus! Say your
distilling your "volatile liquid" and you just greased your joints. That gas is going to touch the grease and possibly react with it and possibly
contaminate what ever it is your distilling. |
It is very unlikely to react with silicone grease.
Volatile liquids do bleed out the joints. Just the other day I was drying some solvents and the methyl ethyl ketone was seeping out of one of joints,
even though I greased it. Stinky stuff.
[Edited on 21-8-2011 by Bot0nist] |
Methyl ethyl ketone = stinky? No! MEK smells like butterscotch; its nice.
My quite small but growing Youtube Channel: http://www.youtube.com/user/RealChemLabs
Newest video: Synthesis of Chloroform
The difference between chemists and chemical engineers: Chemists use test tubes, chemical engineers use buckets. |
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Bot0nist
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Not to me, It chokes me out. It will make your eyes water and your throat close up, trust me.
Kinda like as bad as toluene or MNT/DNT. All smell 'good', but if your get a breath full, you'll know it.
*cough,gag*
[Edited on 22-8-2011 by Bot0nist]
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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User
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If it doesnt hurt the product one could even use some water to make the joints seal, someone pointed this to me once, dont even know if this is such a
good idea..
| Quote: |
As long as your set up isn't closed (why?) then it shouldn't have the pressure needed to escape through the joints. The flow of gas/pressure will flow
out of the set up just like it would with the joints greased unless your glassware is no good or the joints have been damaged. Plus! Say your
distilling your "volatile liquid" and you just greased your joints. That gas is going to touch the grease and possibly react with it and possibly
contaminate what ever it is your distilling.
|
Btw my joints arn't bad, as pointed out by botanist, this just happens, I wish it didnt.
It really sucks when the glass is hot and running.
I can understand the people that dont want to buy the super expensive grease.
Im using the same tube for nearly 2 years,a speck is enough.
The stuff is just good and holds up to above 400 degrees.
What a fine day for chemistry this is.
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CuriosityKilledtheKat
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here is a website that teaches you how to make your own grease/lubricant probably the cheapest way to go about it too i'll have a crack at it one day
soon...
www.instructables.com/id/Personal-Lubricant/
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redox
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You're joking, right?
I'm pretty sure that that recipe gives a horrible grease/lubricant. When the water evaporates you would be left with a white powder (the cornstarch),
which could only contaminate your reaction and it would be bad on the joints.
Also, maybe you didn't realize it, but that was designed to be a personal 
lubricant... who would actually use that?!
[Edited on 26-8-2011 by redox]
My quite small but growing Youtube Channel: http://www.youtube.com/user/RealChemLabs
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MeSynth
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Like I said before lube is not needed unless your glasswares joins are no good aaaannnddddd it is not desired unless a vacuum is being applied
ffooorrrr the reason that even if the distillate doesnt react with the grease it can still cause it to come into solution with the distillate
reeessullttting in contamination of the distillate. Use grease only when it is needed to pull a leak free vacuum, your joints are no good anymore, OR
your highly intelligent brain decides that grease will be needed to insure nothing escapes through the joints and that contamination of the distillate
or product of reaction will not be a problem.
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User
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Oke than the teachers at the lab-school I did were complete morons..
Never mind , not gonna start a flame war.
[Edited on 26-8-2011 by User]
What a fine day for chemistry this is.
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redox
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| Quote: Originally posted by MeSynth | | Like I said before lube is not needed unless your glasswares joins are no good aaaannnddddd it is not desired unless a vacuum is being applied
ffooorrrr the reason that even if the distillate doesnt react with the grease it can still cause it to come into solution with the distillate
reeessullttting in contamination of the distillate. Use grease only when it is needed to pull a leak free vacuum, your joints are no good anymore, OR
your highly intelligent brain decides that grease will be needed to insure nothing escapes through the joints and that contamination of the distillate
or product of reaction will not be a problem. |
YOUR highly intelligent brain obviously forgot about joint freezing. You won't catch me in a million years not using grease on my new Aldrich
Dean-Stark trap, or my three-necked flasks. I don't know if you have any ST glassware, but it really sucks to have a frozen joint, and using lube
greatly lowers the chances of freezing.
My quite small but growing Youtube Channel: http://www.youtube.com/user/RealChemLabs
Newest video: Synthesis of Chloroform
The difference between chemists and chemical engineers: Chemists use test tubes, chemical engineers use buckets. |
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zenosx
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I use a lithium grease "pen" that is basically a stick of lithium grease wrapped in paper. I have been using it for a couple of years now, and as most
have said, I lube the top or middle of the joint, leaving the lowest portion clean. Lubed portions will look "clear." I have never had stuck glassware
using this compound, and have never had it contaminate any distillation/reflux etc that I have been doing.
You do need to use more of it for vacuum distillations, but it has never pulled through the joint into my rigs. I also use it on all of my glass on
glass reagent containers with no issues, including my 98% HNO3 that had managed to eat through any other compound besides glass it was placed in.
A quick half/joint run around with the pen, and a quick twist always has worked, and since it is thick it actually helps to "glue" the joints together
and prevent disconnections.
I find vasoline and others like it too messy and hve only used them when I had a high likelihood of joint freeze (NaOH, etc,)
A question that sometimes drives me hazy: am I or are the others crazy?
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