From: ILPI Support <info**At_Symbol_Here**ILPI.COM>
Subject: Re: [DCHAS-L] Schlenk Line Survival Guide
Date: Wed, 22 Apr 2020 12:18:06 -0400
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: A81D514D-7E12-4AFD-8445-475C872E2477**At_Symbol_Here**

Nice discussion.  I have an intro to vacuum/Schlenk lines here:   It is not intended to be comprehensive, but it does discuss safety and the link to bubblers does discuss mercury in a balanced way - avoid, but if you do use it, take precautions.

You haven't lived until you've used a Toepler pump - over a liter of mercury cycling over and over in the vacuum system.  They are incredibly useful for a very narrow need of collecting and measuring the volume of non-condensable or condensable gases under high vacuum conditions.   I suspect only a small minority of current organometallic chemists have heard of them, let alone know how to use one.  Probably only a handful of them still in existence:

At the start of the cycle, the gas in the system fills the vacuum line and space above the mercury pool.  As the mercury rises, it cuts off the connection to the vacuum system and forces the trapped gases above it into a small narrow tube with a one-way valve.  When the mercury hits an electrical contact, a solenoid automatically lowers the mercury level.  The space above the mercury is now a complete vacuum (except for mercury vapor).  As the column falls further, it eventually reopens the connection to the vacuum system, and the system re-equilibrates at a new and lower pressure than before the first cycle.  The cycle then repeats, each time forcing the collected gas into the collection tube.  Repeat it enough times over several hours and you will eventually force all the gas in the system into the collection tube.  You can then measure the pressure in the collection tube and use PV=nRT to calculate the amount of gas collected.

But wait, there's more!  Suppose you have a collection of gases. You can measure their total pressure and then cycle the collected gas over a catalyst.  So, for example, you can oxidize your hydrogen to water by passing it through a "burn tube" containing a heated copper oxide catalyst.  The water that is formed can then be removed by passage through a cryogenic trap, and you can measure the remaining gases in the system.  You calculate the amount of H2 by the difference between the original and new pressures.

Very nice stuff.  Helped me get a couple of JACS papers as an undergrad.

Rob Toreki

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On Apr 22, 2020, at 11:47 AM, Jack Reidy <jreidy2**At_Symbol_Here**STANFORD.EDU> wrote:

I like this guide ( by Pat Frank at SLAC (although I think he just retired). It does discuss and describe mercury, but clearly states that they are not permitted. I'm more of an analytical chemist by training, though, with no Schlenk-line experience outside of lab classes, so I'm less likely to catch any faults than those with more experience.
Jack Reidy (he/him)
Research Safety Specialist
Environmental Health & Safety
Stanford University
484 Oak Road, Stanford, CA, 94305
Tel: (650) 497-7614
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Pickel, Joseph
Sent: Wednesday, April 22, 2020 3:11 AM
Subject: Re: [DCHAS-L] Schlenk Line Survival Guide
I have to say that I was really excited when I saw and read through this guide that Neal alerted us to.  Having done my graduate research using high vacuum and Schlenk line techniques and seeing so many others struggle to do the same I thought this was a great introduction to this tool that is accessible and in a form that many young scientists will appreciate.
Craig's comments about some of the missing detail and safety details struck me as correct, but misdirected.  This is most definitely a guide and not a treatise on the subject -for that I would recommend The Manipulation of Air Sensitive Compounds"  by Shriver and Drezdzon- Wiley 1986- with the side note that I believe  Neal worked in Shriver's lab way back when. However, when I pulled my copy off the shelf last night- I noted that it also discussed use of mercury devices including mercury diffusion pumps (but it does have a paragraph of info on mercury hazards later in the book).
So my question to Craig and the group is-  is there a better guide on this subject that is as accessible/available and has the appropriate safety information that we could recommend instead? I am not aware of one and would suggest not discounting this guide but rather reaching out to the author and providing him this safety information to supplement his already good guide and make it better.
Joe Pickel
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Craig Merlic
Sent: Tuesday, April 21, 2020 6:06 PM
Subject: [EXTERNAL] Re: [DCHAS-L] Schlenk Line Survival Guide
This Schlenk line guide is a bit simplistic and old-school.  For example:
"The inert gas is vented through a bubbler (either oil or mercury).-".  
Really? mercury bubbler?   We should only be recommending oil.
Rest of same sentence: "allowing the inert gas pressure to be monitored."
Not really.  It does allow one to see the flow of inert gas, but not truly monitored.  The function of the bubbler is to provide a small positive pressure so when one releases an evacuated flask to inert gas the system should not have negative pressure and suck in oil/air.
Missing from diagram - Since a taller column of oil is necessary to achieve the same positive pressure of inert gas, a trap should be placed between the inert gas manifold and the bubbler to catch oil moving towards the inert gas manifold.
Missing from diagram - An inert gas ballast should be connected to the inert gas manifold.  My students use a 1 L flask so that when a larger evacuated flask is switched to inert gas the drop in inert gas manifold pressure is not so great as to suck oil back into the system.  Too much pressure reduction and air could be sucked in after the oil.
The guide does not include information about usage, mainly just startup and shutdown.  So maybe a starting point, but not a guide to usage.
Craig A. Merlic
Professor of Chemistry, UCLA Department of Chemistry and Biochemistry
Executive Director, UC Center for Laboratory Safety
Los Angeles, CA  90095-1569
Voice:  310-825-5466
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> on behalf of NEAL LANGERMAN <neal**At_Symbol_Here**CHEMICAL-SAFETY.COM>
Organization: Advanced Chemical Safety
Reply-To: <neal**At_Symbol_Here**CHEMICAL-SAFETY.COM>
Date: Tuesday, April 21, 2020 at 9:50 AM
To: <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Subject: [DCHAS-L] Schlenk Line Survival Guide
ASYNT has updated its SCHLENK LINK SURVIVAL GUIDE.  Very helpful for those new to vacuum techniques or as a sanity check for the pro.
Stay healthy and stay safe
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