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Subject: Re: FW: Lithium Aluminum Hydride & friction as an ignition source
Date: Thu, 30 Jun 2011 06:59:42 -0700
Author: NEAL LANGERMAN 		Next by Date:
Subject: Re: Lithium Aluminium Hydride & friction as an ignition source
Date: Thu, 30 Jun 2011 12:56:24 +0000
Author: Paul Dover


Date: Thu, 30 Jun 2011 09:06:30 -0400
Reply-To: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
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From: ILPI <info**At_Symbol_Here**ILPI.COM>
Subject: Re: FW: Lithium Aluminum Hydride & friction as an ignition source
In-Reply-To: <BE28425130279043A5B92A2BC7116E233F7313**At_Symbol_Here**EXCH-MBOX-1.exch.ucr.edu>

According to http://www.chemetalllithium.com/fileadmin/files_chemeta ll/Downloads/DL_LAH_CMYK.pdf which references primary literature I do not have current access to: 

In the absence of air the thermal decomposition of LiAlH4 begins at 125=B0C whereby hydrogen is liberated. At the same time finely distributed aluminum is formed: 

3 LiALH4 --> Li3AlH6 + 2 Al + 3 H2

This decomposition step is endothermic. At 200=B0C Li3AlH6 itself decomposes into LiH, Al and H2; the ultimate decomposition products are LiAl and H2 (430=B0C)3,4. 

3 J.A. Dilts, E.C. Ashby, Inorg. Chem. 11, 1230 (1972)

4 T.N. Dymova, D.P. Aleksandrov et al., Russian J. Coordination Chem. 1994, 20, 279-285 and 1995, 21, 175-182. 

Friction can no doubt exceed 125 C, and when you are making finely divided aluminum (which can be pyrophoric) and hydrogen, ignition in air is not all that surprising.  Presumably, the endothermic nature of the decomposition is why there is no autocatalytic friction-induced decomposition under inert atmosphere.

If someone has access to the literature, perhaps the decomposition under air is also discussed in one of those references.

Rob Toreki

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On Jun 29, 2011, at 8:13 PM, Russell Vernon wrote:

Dear Chemical Safety Experts,
One of the labs on our campus had a fire when the researcher scraped lithium aluminum hydride (LiAlH4) out of the glass jar in which it was packaged. The LiAlH4 was old and the researcher was using a dry metal spatula. A quick review of the manufacturer=92s Material Safety Data Sheet informed the user of moisture sensitivity but there is no indication of friction causing a fire.
The supervising faculty member reported personal knowledge that friction can cause ignition of LiAlH4.
The manufacturer (Sigma-Aldrich) of this material was contacted and responded:
From: Gregory Stachowiak [mailto:Gregory.Stachowiak**At_Symbol_Here**sial.com] On Behalf Of Sigma-Aldrich Technical Service
Sent: Friday, June 24, 2011 8:17 AM
To: Russell Vernon
Cc: Chantalle Carver
Subject: RE: 199877 -- Lithium Aluminum Hydride
Hello again Russell, 

We do not have any data on-hand suggesting that friction alone could cause ignition, however, all of our handling of this chemical is performed inside a glove bag under a completely inert atmosphere (argon specifically).  This inert atmosphere, combined with the idea that we don't "spread the product out over a large, flat, combustible surface" is likely why we have never had any issues with fires starting during the packaging process. 

As shown by those links, however, such an ignition does appear to be possible.  All we can recommend is handling this product under argon in a glove box or a glove bag to minimize the oxygen and moisture contact and therefore minimize the chances of a fire. 

Unfortunately, because we have not had issues with this problem, we do not have a specific written procedure for weighing it, no. 

Best regards,
Gregory Stachowiak

SIGMA-ALDRICH

Gregory Stachowiak / Scientist, Technical Service Associate 
Technical Services 
6000 N Teutonia Avenue / Milwaukee WI 53209 / USA 
P: (800) 231-8327, x5326 / Gregory.Stachowiak**At_Symbol_Here**sial.com
sigma-aldrich.com

http://cameochemicals.noaa.gov/chemical/989

http://www.chemicalbook.com/ChemicalProductProperty_EN_CB7318252.htm   

http://www.erowid.org/chemicals/dmt/dmt_synthesis1..shtml       ;     scroll down to step 3:

http://web.princeton.edu/sites/ehs/labsafetymanual/cheminfo/lah.htm

So it appears likely that friction alone in the presence of air may be able to ignite lithium aluminum hydride.
You may want to evaluate your own use and written procedures to prevent this from happening in your world.
Sincerely,
-Russ
Russell Vernon, Ph.D.
Director
Environmental Health & Safety
University of California, Riverside
900 University Ave
Riverside, CA 92521
Direct (951) 827-5119
Admin (951) 827-5528
Fax (951) 827-5122



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