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Date: Tue, 6 Jan 2009 10:07:01 -0500
Reply-To: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Subject: Re: UCLA Lab Fire
From: "Pickel, Joseph M."
Date: January 6, 2009 9:36:20 AM EST (CA)
Subject: RE: [DCHAS-L] UCLA Lab Fire
Folks-
For what its worth, having worked in the lab for almost 10 years with
n-BuLi, sec-BuLi, and t-BuLi, and a variety of their derivatives, I am
dismayed by some of the advice given in the previous message. The
incorporation of opinions and speculation takes away from the fact
that alkyl lithiums are truly hazardous materials and whether or not
the author agrees with the facts of the newspaper article, it seems
that in one way or another, some poor student has sustained serious
burns by coming into contact with an alkyl lithium compound. That
being said--- these materials can be handled safely (even in sure-seal
bottles) by personnel who understand the hazards of the material and
take the appropriate precautions.
I will not go into great detail about what precautions must be taken
to handle alkyl lithiums and other pyrophoric materials, but I do want
to dispel some of the generalizations proposed in the previous note
- ***The pyrophoricity of alkyl lithiums will depend on concentration,
solvent, humidity etc... generalizations ala t-BuLi will be more
pyrophoric than n-BuLi are not necessarily accurate or helpful and no
one should be given the idea that a t-BuLi is significantly more
dangerous than others! Alkyl lithiums come in a variety of solvents at
a variety of concentrations and almost every one of these solutions
will catch fire if exposed to a suitably humid atmosphere. That being
said, the author of the previous letter was probably working with a
very old and therefore less concentrated bottle of n-butyl lithium
when he got it on his hand which is why it didn't burn.
- Sure-seal bottles aren't perfect, but they provide a safe way to
handle alkyl lithium solutions in a bench top environment. Unless the
seal is punctured by a very large gauge syringe or a nail, the seal is
sufficient to prevent moisture from entering the bottle and causing
big problems.
- The technique described below for withdrawing/dispensing solutions
from a sure-seal bottle is the lazy/ quick and dirty way of doing
things and can lead to significant hazards- I would not recommend them
to anybody. Better methods are described in the Aldrich technical
bulletin cited here-http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Bulletin/al_techbull_al134.Par.0001.File.tmp/al_techbull_al134.pdf
- I agree that purchasing large containers of chemicals for purposes
of cost savings is a bad idea, but that statement ignores the problem
of how to tell an ordinary chemist with a limited budget about the
merits of small containers. However, purchasing alkyl-lithium
compounds in small bottle is a no-brainer even for the thrifty
chemist! You see- even in the best storage conditions (complete
sealed from the atmosphere under an inert gas blanket and in the
Fridge) alkyl lithium compounds degrade over time to more stable
components. Therefore, the concentration of the alkyl lithium
solution marked on the label is almost always higher than what is
actually in the bottle. That means for a given reaction- the chemist
must either determine the concentration of the solution prior to each
use or use an increasingly large excess of solution for each
experiment... either one of the workaround techniques is less cost-
efficient that buying a small bottle on an as needed basis.
Be safe,
Joseph M. Pickel, Ph.D., CCHO
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