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Biochemscientist
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[*] posted on 18-8-2011 at 22:43
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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[*] posted on 18-8-2011 at 22:55


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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[*] posted on 19-8-2011 at 03:12


Also, look for plumbers silicon grease. It is very unreactive and a lot cheaper than buying 'vacuum grease.'



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[*] posted on 19-8-2011 at 03:50


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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[*] posted on 19-8-2011 at 04:00


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




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[*] posted on 19-8-2011 at 04:13


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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[*] posted on 19-8-2011 at 05:27


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.


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!:D

[Edited on 19-8-2011 by Bot0nist]




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[*] posted on 19-8-2011 at 05:43


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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[*] posted on 19-8-2011 at 08:08


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.




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[*] posted on 20-8-2011 at 11:06


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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[*] posted on 20-8-2011 at 13:16


I use vaseline or nothing.
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[*] posted on 20-8-2011 at 15:41


Plumbers waterproof grease (HOME DEPOT) or REESE trailer ball hitch lubricant (TEFLON) found at many autopart stores, and outdoor sports stores



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[*] posted on 20-8-2011 at 22:48



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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[*] posted on 21-8-2011 at 14:23


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.
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[*] posted on 21-8-2011 at 14:32


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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[*] posted on 21-8-2011 at 15:20


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]




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[*] posted on 21-8-2011 at 15:36


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.




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[*] posted on 21-8-2011 at 18:11


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*:o

[Edited on 22-8-2011 by Bot0nist]




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[*] posted on 22-8-2011 at 01:39


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.




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[*] posted on 25-8-2011 at 19:25


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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[*] posted on 25-8-2011 at 19:49


Quote: Originally posted by CuriosityKilledtheKat  
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/


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?!:o




[Edited on 26-8-2011 by redox]




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[*] posted on 26-8-2011 at 00:50


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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[*] posted on 26-8-2011 at 02:58


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]




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[*] posted on 26-8-2011 at 06:48


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.




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[*] posted on 5-2-2013 at 20:34


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,)




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