From: David G. Naugler, Ph.D. (dnaugler$##$sfu.ca)
Date: Mon Apr 01 2002 - 14:27:49 EST
Sam,
To say that aluminum hydroxide is hydrated alumina is about as useful and
meaningful as to say that alumina is desiccated aluminum hydroxide. Alumina
comes in two polymorphs, alpha and gamma and above 1000 C. alpha is the
thermodynamically stable form. Likewise above 1000 C. any hydrated form of
hydrated alumina with stoichiometries such as AlO.OH or Al(OH)3 will be
converted into alpha alumina. However, alpha alumina is indefinitely
metastable at low temperatures so you cannot go the other way.
I have prepared aluminum hydroxide as the undesired end product from the
neutralization of LiAlH4 during a hydride reduction. The formation of
aluminum hydroxide or various forms of hydrated alumina are the natural
consequence of aqueous chemistry of aluminum salts. Aluminum is strictly
trivalent and aqueous complexes of aluminum salts have amphoteric character.
Addition of ammonia to a boiling solution of any aluminum salt gives AlO.OH
The true hydroxide, Al(OH)3, is obtained as a crystalline white precipitate
when carbon dioxide is passed into alkaline "aluminate" solutions.
d
----- Original Message -----
From: sam
To: Multiple recipients of list orglist
Sent: Saturday, March 30, 2002 11:05 PM
Subject: ORGLIST: preparation of aluminum hydroxide
Dear All
I need to use aluminum hydroxide for a purification. Merck Index says it
is merely hydrated alumina. Does any body know about the procedure or
experience doing aluminum hydroxide(hydrated alumina) and willing to
pass it on to me.
thanks in advance
sam
__________________
ORGLIST - Organic Chemistry Mailing List
Website / Archive / FAQ: http://www.orglist.net/
List coordinator: Joao Aires de Sousa (jas$##$mail.fct.unl.pt)
This archive was generated by hypermail 2.1.4 : Fri Sep 19 2003 - 12:16:54 EDT