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 H2This 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.
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 HydrideHello 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.
Gregory Stachowiak / Scientist, Technical Service Associate
6000 N Teutonia Avenue / Milwaukee WI 53209 / USA
P: (800) 231-8327, x5326 / Gregory.Stachowiak**At_Symbol_Here**sial.com
http://www.erowid.org/chemicals/dmt/dmt_synthesis1..shtml   ; scroll down to step 3: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,-RussRussell Vernon, Ph.D.DirectorEnvironmental Health & SafetyUniversity of California, Riverside900 University AveRiverside, CA 92521Direct (951) 827-5119Admin (951) 827-5528Fax (951) 827-5122