Sciencemadness Discussion Board - Refluxing

Refluxing

#maverick# - 9-6-2011 at 17:16

i was refluxing for the first time ever today, is the whole setup supposed to be closed, and i noticed at the top of my column the glass stopper kept popping off, its probably cuz i lacked a keck clip and the silicone kind of melted might it be because i didnt apply it thick enough, im sorry this is my first time ever refluxing/disitilling.

setup:

grease i used: http://www.lowes.com/pd_53861-1366-88693_0__?productId=10921...

Magpie - 9-6-2011 at 17:54

You should never heat a closed glassware system.

The purpose of the reflux column is to condense vapors from the pot, which then fall back into the pot. So there is no need to try to contain them by sealing.

It looks like your glassware acquisitions are way ahead of your knowledge. You should get a good organic lab manual and read that beforehand.

Rogeryermaw - 9-6-2011 at 19:14

absolutely correct magpie. if you need to control the atmosphere in your system, use inert gas. a reflux should be performed in an open system. good thing it wouldn't seal or you may have lost some nice glass or worse. better a joint to give out than for the glass to fail.

edit: if the grease you're using is melting, try automotive dielectric grease. a lot of people here have used it with success. personally i wouldn't know. i got vacuum grease at elemental for fairly cheap, but many claim great success with the electronic grease.

[Edited on 10-6-2011 by Rogeryermaw]

#maverick# - 9-6-2011 at 19:14

Quote: Originally posted by Magpie

You should never heat a closed glassware system.

The purpose of the reflux column is to condense vapors from the pot, which then fall back into the pot. So there is no need to try to contain them by sealing.

It looks like your glassware acquisitions are way ahead of your knowledge. You should get a good organic lab manual and read that beforehand.

Will do magpie. Actually I have vogels practical chem book. I'll practice my techniques and with time I will get it

#maverick# - 9-6-2011 at 19:23

Quote: Originally posted by Rogeryermaw

absolutely correct magpie. if you need to control the atmosphere in your system, use inert gas. a reflux should be performed in an open system. good thing it wouldn't seal or you may have lost some nice glass or worse. better a joint to give out than for the glass to fail.

edit: if the grease you're using is melting, try automotive dielectric grease. a lot of people here have used it with success. personally i wouldn't know. i got vacuum grease at elemental for fairly cheap, but many claim great success with the electronic grease.

[Edited on 10-6-2011 by Rogeryermaw]

Wow. I feel a bit incompetent lol. And yea I'll try that or some Teflon tape. Once I have read up more on refluxing and distilation

Rogeryermaw - 9-6-2011 at 19:38

dude, don't be down on yourself. if you added the knowledge of everyone on this site into one person he would still have a long way to go. the good thing is that you are using your brain for something other than keeping your head from caving in. but there is a lot of good knowledge here so asking questions is a good start and most here will be glad to offer help for you as they have done for me and several others.

Magpie - 9-6-2011 at 19:39

Vogel's is good. But for instruction in laboratory techniques I recommend the last book on this list by Pavia et al:

http://www.abebooks.com/servlet/SearchResults?an=Pavia+et+al...

#maverick# - 9-6-2011 at 19:50

Quote: Originally posted by Rogeryermaw

dude, don't be down on yourself. if you added the knowledge of everyone on this site into one person he would still have a long way to go. the good thing is that you are using your brain for something other than keeping your head from caving in. but there is a lot of good knowledge here so asking questions is a good start and most here will be glad to offer help for you as they have done for me and several others.

thank you for the kind words

#maverick# - 9-6-2011 at 19:52

Quote: Originally posted by Magpie

Vogel's is good. But for instruction in laboratory techniques I recommend the last book on this list by Pavia et al:

http://www.abebooks.com/servlet/SearchResults?an=Pavia+et+al...

looking into it as we speak

#maverick# - 9-6-2011 at 21:13

ok ill have another go at ethyl acetate soon, its a simple synthesis, thank you for your help guys

blogfast25 - 10-6-2011 at 04:35

Nice spiral cooler. But total overkill in all likelihood. A much cheaper Liebig cooler (air or water cooled) or even a nice Vigreux column cooled with damp cloth will suffice for refluxing water based reactions, extractions or whatever takes your fancy.

Make sure you don't break that baby now... by top stoppering for instance

and don't forget boiling stones!

[Edited on 10-6-2011 by blogfast25]

Arthur Dent - 10-6-2011 at 06:12

If you need to reflux while preventing air from entering the vessel, use a tapered vent at the top of your column connected through a tube to a bubbler filled with whatever inert/neutralizing liquid recommended for your reaction, use an empty conical flask with sidearm between the column and the bubbler because as soon as you remove the heat, a vacuum effect will quickly draw in air, pushing back the liquid of your bubbler back to the reaction vessel.

A nice setup you have. Yeah, I second Rogeryermaw suggestion of silicone dielectric grease from the auto parts store, it hasn't failed me so far.

Robert

The WiZard is In - 10-6-2011 at 06:12

Quote: Originally posted by #maverick#

Wow. I feel a bit incompetent lol. And yea I'll try that or some Teflon
tape. Once I have read up more on refluxing and distilation

This being a science form a less forgivingly person would
mention something from Chem. 101 — Boyle-Mariotte Law.

Once your apparatus reaches operating temperature you could
stopper it off, however .... when you turn the heat off you will
create a vacuum making it difficult to remove the stopper, and
possibly imploding you glassware.

The WiZard is In - 10-6-2011 at 06:52

Quote: Originally posted by Magpie

Vogel's is good. But for instruction in laboratory techniques I recommend the last book on this list by Pavia et al:

http://www.abebooks.com/servlet/SearchResults?an=Pavia+et+al...

Think big go for the 4th edition.

Amazon.com

INTRODUCTION TO ORGANIC LABORATORY TECHNIQUES
A Microscale Approach (Brooks/Cole Laboratory Series for Organic Chemistry) [Hardcover]

List Price: $252.95
Price: $196.18 & this item ships for FREE with Super Saver Shipping.

#maverick# - 10-6-2011 at 07:24

Quote: Originally posted by The WiZard is In

Quote: Originally posted by #maverick#

Wow. I feel a bit incompetent lol. And yea I'll try that or some Teflon
tape. Once I have read up more on refluxing and distilation

Thanks. Idk in a moment of stupidity I'm like I should stopper it off. Against my better judgement and knowledge.

[Edited on 10-6-2011 by #maverick#]

#maverick# - 10-6-2011 at 07:27

Quote: Originally posted by blogfast25

Nice spiral cooler. But total overkill in all likelihood. A much cheaper Liebig cooler (air or water cooled) or even a nice Vigreux column cooled with damp cloth will suffice for refluxing water based reactions, extractions or whatever takes your fancy.

Make sure you don't break that baby now... by top stoppering for instance

and don't forget boiling stones!

[Edited on 10-6-2011 by blogfast25]

Thanks. Yea I had boiling stones. I'll make sure to take good care of it. And I'll be on the lookout for a liebig

The WiZard is In - 10-6-2011 at 08:20

Quote: Originally posted by #maverick#

i was refluxing for the first time ever today, is the whole setup supposed to be closed, and i noticed at the top of my column the glass stopper kept popping off, its probably cuz i lacked a keck clip and the silicone kind of melted might it be because i didnt apply it thick enough, im sorry this is my first time ever refluxing/disitilling.

I would mention in passing — a coil condenser is not mechanically
ideal for refluxing. It is designed for straight through use, i.e.,
vapour in one end - distillate out the other. To much
heat and you will be blowing your chems out of the top of la
condenser. An Allihn bulb condenser is de rigeueu.

I know - Wili-P shows a coil condenser being used for
refluxing, however, note that it is being done under
vacuum/reduced pressure.

[Edited on 10-6-2011 by The WiZard is In]

#maverick# - 10-6-2011 at 11:08

Quote: Originally posted by The WiZard is In

Quote: Originally posted by #maverick#

i know its not ideal but it will have to do until i get a liebig or vigereux

turd - 10-6-2011 at 13:42

Apart from the correct objection concerning the coil-condenser, why is everybody using those silly plastic clamps? They break easily, melt easily and - worst of all - look embarrassingly n00bish.

#maverick# - 10-6-2011 at 13:49

Quote: Originally posted by turd

Apart from the correct objection concerning the coil-condenser, why is everybody using those silly plastic clamps? They break easily, melt easily and - worst of all - look embarrassingly n00bish.

Instead of asking why. Ask yourself why not?

turd - 10-6-2011 at 13:52

I already gave the answer to that question.

redox - 10-6-2011 at 14:00

Quote: Originally posted by The WiZard is In

Quote: Originally posted by Magpie

Vogel's is good. But for instruction in laboratory techniques I recommend the last book on this list by Pavia et al:

http://www.abebooks.com/servlet/SearchResults?an=Pavia+et+al...

I bought this book (albeit an older edition), for $10 dollars including shipping! I don't think the newer versions are all that different.

#maverick# - 10-6-2011 at 14:28

Quote: Originally posted by turd

I already gave the answer to that question.

Lol. Well I got em on the cheap and anything extra to help protect my investment doesn't hurt so why not?O

Rogeryermaw - 10-6-2011 at 16:38

i find that, under reduced pressure, the apparatus usually holds itself together well with no clips. sometimes to the point of being difficult to disassemble. also, they have been terribly frustrating due to how easily they break on me. until i find myself trying pressurized processes regularly, i probably will find their use limited. if i really do need a clip it's pretty easy to bend one out of copper wire. they're not incredibly strong, but they work. just be careful not to try to force one over glass if it's too tight as scratches are detrimental to the longevity of your equipment.

Magpie - 10-6-2011 at 17:39

I like the clips, especially those made of ptfe, because they assure that the joint is well seated, and I can manipulate the assembly without it falling apart and breaking. I leave one joint unclipped, usually one with a joint pointing straight up, as a safety relief valve of sorts. If enough pressure has built up to overcome the viscosity of silicone grease I want it to open up. I admit that they do look rather noobish, however.

#maverick# - 10-6-2011 at 17:44

yea they do look noobish but why not, also another question what do you guys use to get the silicone grease of the joints i have cleaned with soap and warm water, soaked it in and it still drys with some residue,

entropy51 - 10-6-2011 at 18:07

Quote: Originally posted by #maverick#

yea they do look noobish but why not, also another question what do you guys use to get the silicone grease of the joints i have cleaned with soap and warm water, soaked it in and it still drys with some residue,

There's an app, I mean thread for that.

#maverick# - 10-6-2011 at 18:32

Quote: Originally posted by entropy51

Quote: Originally posted by #maverick#

There's an app, I mean thread for that.

i like ur pun =)