09-24-03 13:30
No 460789
I have a question about possible hairline crack symptoms during a distillation.
A three-way adapter dropped. Thermometer broken: ok, replaced. Small chip on the top lip, where the thermometer typically goes, but the teflon themometer adapter gasket fits well under that, no perceived problem there. After the drop, there were some bubbles observed at the adapter/reaction flask joint. Cleaned up the joints, regreased, no obvious leaks. However, now, when distilling, the reflux front gets to the adapter/reaction flask joint, then takes approx an hour to go further. Eventually the distillation does get done, but it is taking much higher heat plate settings, faster spin rates, and about twice as long. Vacuum is typical of pre-incident levels, and steady. Indeed the vacuum is the same as if one were to block the tubing withour hooking up to glassware.
Is the adapter cracked? Can there be an "invisible" crack? Could a crack cause these symptoms? Is reality breaking down? I hate it when that happens, I prefer it to be enhanced. Anyone care to venture a cause and solution?
Tolerance is a sign of maturity.
(Newbee)
09-24-03 13:44
No 460791
to have a hair line crack.P is assuming you checked everything else, even going back to the pump and thermometer gasket.P had this problem once, and after a little thought, did this:cleaned every thing that was glass,washed,rinsed with methanol,and assembled .P had some liquid food colouring and with gloves on and a syringe,cranked up the vacuum and dripped the food colouring around the joints,and the dye got sucked in..it was then that P found a teeny invisible crack.If this doeesn't work,maybe dip the whole (now rigid) assembly under vac into water with a little soap in it,not foamy though.P hopes when the soapy watergets sucked through the crack, it will make a bubble or mess on the inside.
(Stranger)
09-24-03 16:43
No 460832
Thanks for the input. I may try the food coloring method - good idea. Submersion of the apparatus is not practical for me, though brushing soapy water onto the system might work. One question: the food coloring cleaned off easily? I think it's water soluble, but tell that to my fingers around Easter, LOL.
What I really need to know is are these the symptoms one would expect of a vacuum leak? Now that I rephrase it, I realize I never searched for vacuum leak. Oh well, maybe I can spell it for the flamers out there: imbecile
Senility means living in the present.
(Newbee)
09-24-03 21:35
No 460902
not aproblem, glad to help out a fellow Newbee.The colouring may get into the ground glass,but who cares..it will just brighten things up a little.P got the red on his fuc#*in nose and walked around looking like a boozer for 3 days....P now wears gloves for everything.And yes the raising temps are the first clue.
(Legba)
09-25-03 00:18
No 460932
If submerging everything and placing under a vacuum is not an option then pressurize everything and place liquid dishsoap on the outside, bubbles will form where ever a leak is present. A simple leak should be present by doing no more than blowing into the sealed system after applying soap, if its a difficult leak then you can easily and cheaply pressurize everything by picking up a $12.00 bottle of Nitrogen from any welding or Air Conditioning parts supplier in your area.
If in doubt and the equipment is in question, just replace it and avoid undesired ill effects. You wouldn't have to physically submerge everything to test for a vacuum leak though, just mix liquid dish soap with a little water in a spray bottle and mist it around the suspect area with your vacuum pump connected and running, the bubbles will show up on the inside if there is a leak.