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Author: Subject: Rubber stoppers, or Glass Joints?
SimplyChem
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Rubber stoppers, or Glass Joints?

Hello All
I am a bit new to chemistry, but am looking to purchase a distillation apparatus to distill some nitric acid and things of the like.

(I will post a photo of the apparatus I have been looking at. Seems good enough for a beginner like me )

After reading that someone's rubber stopper melted, I am debating on whether or not to purchase a rubber stopper to fit my boiling flask, or a glass joint. (70 degrees?)

Also, I don't want to risk getting glassware stuck together, as I don't really want to pay $30 for some Corning grease. Anyway, experiences and input would be greatly appreciated. - A fellow noob. Chemosynthesis International Hazard Posts: 1071 Registered: 26-9-2013 Member Is Offline Mood: No Mood I always use glass. For most hobby activities, vaseline is actually a decent substitute for greasing your joints. TheChemiKid National Hazard Posts: 493 Registered: 5-8-2013 Location: ̿̿ ̿̿ ̿'̿'̵͇̿̿з=༼ ▀̿̿Ĺ̯̿̿▀̿ ̿ ༽ Member Is Offline Mood: No Mood Buy a glass joint. Nitric Acid will completely destroy any plastic or rubber. The glass may be more expensive, but it will serve you in the long run. When the police come \( * O * )/ ̿̿ ̿̿ ̿'̿'̵͇̿̿з=༼ ▀̿̿Ĺ̯̿̿▀̿ ̿ ༽ SimplyChem Harmless Posts: 3 Registered: 27-3-2014 Location: California Member Is Offline Mood: Spontaneous Thanks for the input! I had thought Vaseline would work Haha, just hoping it doesn't react with anything. That would be an unpleasant surprise. Its just a shame most glassware I see online is so expensive. Seems a bit much for what it is. this "Distillation Adapter, 75° 3-way, 24/29" I have been looking at is 20 dollars! HeYBrO National Hazard Posts: 289 Registered: 6-12-2013 Location: 'straya Member Is Offline Mood: try ebay. type the size joint you want and a plethora of kits should appear. Ask Dr.Bob, he is a member here who sells second hand glassware that is in immaculate condition (most is new intact) and his prices cannot be matched. It is a sticky thread in the reagents and equipment thread. Have fun! SimplyChem Harmless Posts: 3 Registered: 27-3-2014 Location: California Member Is Offline Mood: Spontaneous Thanks! thebean Hazard to Others Posts: 116 Registered: 26-9-2013 Location: Minnesota Member Is Offline Mood: Deprotonated Use glass joints. Also someone said that vaseline makes good lube. It's decent but I prefer silicon plumber's lube. It's more heat resistant. "You need a little bit of insanity to do great things." -Henry Rollins Steam Hazard to Others Posts: 237 Registered: 25-3-2014 Location: Minnesota Member Is Offline Mood: Triple Point If you really want to get fancy you can shell out the extra$7.50 and purchase a thing of dow highvac grease! ;)

DISCLAIMER: The information in this post is provided for general informational purposes only and may not reflect the current law in your jurisdiction. No information contained in this post should be construed as legal advice from the individual author, nor is it intended to be a substitute for legal counsel on any subject matter. No reader of this post should act or refrain from acting on the basis of any information included in, or accessible through, this post without seeking the appropriate legal or other professional advice on the particular facts and circumstances at issue from a lawyer licensed in the recipient’s state, country or other appropriate licensing jurisdiction.
thesmug
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 Quote: Originally posted by Steam If you really want to get fancy you can shell out the extra $7.50 and purchase a thing of dow highvac grease! Wow! Where does one find this so cheaply? Also to OP, based on what you've said, I think you're buying from Homesciencetools, correct? I have their standard organic chemistry glassware kit and it's very good quality and extremely useful for many procedures, however it is extremely expensive. I would suggest you get something with similar or identical parts as a starting point (though I don't think you probably need a fractionating column). Of course buy it from somewhere cheaper. ParadoxChem126 Hazard to Others Posts: 104 Registered: 5-4-2013 Location: USA Member Is Offline Mood: No Mood Teflon tape can also be used to seal ground joints. In some ways, it is better than grease because it does not usually dissolve in solvents. Grease can sometimes dissolve in the reaction solvent and contaminate the product.  Quote: Originally posted by SimplyChem Also, I don't want to risk getting glassware stuck together, as I don't really want to pay$30 for some Corning grease.

Ground joints can usually be separated by applying a little heat from a hot air gun. The heat causes the outer joint to expand slightly, allowing the inner one to be pulled out.

I agree that you should invest in a ground glass apparatus. They are much more versatile and convenient than traditional rubber stopper setups.

Zyklon-A
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Petrolium jelly will melt with very little heat. Get all glass.

thesmug
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 Quote: Originally posted by Zyklonb Petrolium jelly will melt with very little heat. Get all glass.

I think he was asking about sealing said glass joints. Still a very good point, though.
Zyklon-A
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Yeah, I know. I guess a very thin coat might not be affected even if it is above it's melting point.
It will also vaporize slowly above it's melting point.

Chemosynthesis
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 Quote: Originally posted by Zyklonb Yeah, I know. I guess a very thin coat might not be affected even if it is above it's melting point. It will also vaporize slowly above it's melting point.

Definitely not ideal, but it's an old trick from Kubrick, iirc.
MrHomeScientist
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I use silicon "faucet grease" from the plumber's section (I can't remember the actual name - it comes in a little round grey plastic container). I'm wary of using teflon tape, because if you don't wrap it just right the seal can be compromised. They do make teflon sleeves specifically for ground glass joints that sound very nice, but are quite expensive.

If you're reluctant about splurging on expensive grease, just remember that one tube of grease will last you forever!
hissingnoise
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And there's always Glindemann?

Funkerman23
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 Quote: Originally posted by hissingnoise And there's always Glindemann?
A great solution, were it not for the main seller of said rings. According to the homepage linked, its sold by Sigma. Not really an option for us amateurs unless a new seller emerges.

[Edited on 28-3-2014 by Funkerman23]

" the Modern Chemist is inundated with literature"-Unknown
Chemosynthesis
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Obviously your mikeage may vary, but I generally only even use grease when applying vacuum, inert atmosphere, and sometimes drying tubes anyway. Perhaps the seldom prolonged alkaline reaction, but I have been able to avoid joint seizing with prompt and routine cleaning. I keep forgetting about those Teflon sleeves and tape since I never worked in a lab that used them on anything I did.

More on rubber... it can not only melt, but react. The ability to drill holes or make slits in them is what makes them most useful, in my opinion. Additionally, old rubber loses some of its plasticity for a variety of reasons (ex. leaching and perhaps UV polymerization) over time. Properly respected glass should last you a long time.
*FWOOSH*
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NEVER use rubber on vacuum setups, I've had a stopper get pulled so tightly into a joint under simple aspirator vacuum that it actually SHATTERED a piece of glassware
Chemosynthesis
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 Quote: Originally posted by *FWOOSH* NEVER use rubber on vacuum setups, I've had a stopper get pulled so tightly into a joint under simple aspirator vacuum that it actually SHATTERED a piece of glassware

Excellent advice. I hadn't even thought of that... however, I would add the caveat that you may use rubber stoppers in vacuum if there is some kind of pressure release hole drilled in, such as having two holes to link a thick walled flask in series while serving as a water/vacuum trap.

 Sciencemadness Discussion Board » Fundamentals » Reagents and Apparatus Acquisition » Rubber stoppers, or Glass Joints? Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues