Is Vaseline a good alternative for ground glass joint grease(in moderation of course)?paulr1234 - 25-12-2011 at 19:29
It might be an adequate lubricant but it is not inert (it is a mixture of long chain hydrocarbons). It really depends on the reaction you are
planning. PTFE plumbing grease might be a better, also easily available and cost effective alternative but it isn't inert either.nerdalert226 - 25-12-2011 at 20:27
cool,thanks!zoombafu - 25-12-2011 at 21:15
If you are doing anything that requires a vacuum i recommend DOW corning vacuum grease, its expensive, but a tube will last you forever, and it is
probably some of the best quality out there.Endimion17 - 26-12-2011 at 06:24
It is a perfectly good alternative if there aren't high temperatures involved, combined with things like bromine.
For example, a thin layer on the top of the seal is perfect enough for distilling ether. Dessicator lid sealing is also one of the things where it can
find its purpose.
Save silicon grease for more demanding experiments...Arthur Dent - 26-12-2011 at 10:18
There have been many threads on this... again, i'll mention one particular type of grease that I have discovered is nearly 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 adequate, 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.
Teflon tape is adequate, but unless you tape the joint perfectly without the slightest crease in the tape, it won't be a good sealed joint.
I should also add that teflon has a rather high coefficient of thermal expansion. I was using the yellow gas line teflon tape (which is thicker) and I
cracked the female joints of three 500ml RBFs before I figured out why.Arthur Dent - 26-12-2011 at 11:32
I should also add that teflon has a rather high coefficient of thermal expansion. I was using the yellow gas line teflon tape (which is thicker) and I
cracked the female joints of three 500ml RBFs before I figured out why.
Ack!
Thanks for the advice. I'll stick to the grease then. The only time I use teflon tape is when I actually store my glassware and plug it with a ground
glass stopper in just to avoid joints freezing together, and it avoids dust gathering in the vessel.
Robert neptunium - 30-12-2011 at 08:19
DOW corning as mentioned before isnt super expensive ... works with acid, moderatly high temperature and of course vacuum...and high voltages !
think i bought 2 tubes in 2001 ...still hasnt started the second onehissingnoise - 30-12-2011 at 08:34
Glindemann rings can be used in vacuum distillation (two on each male joint), if you can get them . . .
BromicAcid - 30-12-2011 at 09:23
I love those Glindemann rings, I used to use them all the time for my 10/30 thermometer joints since they were too hard to clean out when they got
grease in them.Panache - 2-1-2012 at 18:10
Thats what i figured, i'm going to try to make some using some teflon film and concentric punches, then squeezing the rings out to tubes on the joint. Hexavalent - 7-1-2012 at 09:53
This thread should be in the reagents and apparatus section, no? Arthur Dent - 8-1-2012 at 06:10
Yes it should, but we love living on the edge... LOL
Robert Hexavalent - 8-1-2012 at 12:17
When I first came to the forum, I was told off for posting outside of the appropriate section and creating new threads even where original ones
existed . . .Hexavalent - 13-1-2012 at 15:04
I've recently discovered that when you store glassware with ground glass joints putting a thin sheet of filter paper between the male and female parts
really helps sticking and eliminates dust etc. getting in.zoombafu - 13-1-2012 at 16:44
I've recently discovered that when you store glassware with ground glass joints putting a thin sheet of filter paper between the male and female parts
really helps sticking and eliminates dust etc. getting in.
Good idea, I'll have to try that. Currently I don't put stoppers in any of my ground glass for storage, because one time I had a volumetric flask
stoppered up, and it got locked, I eventually got it out, but it took a while.
