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On page 1176 in the September 2001 (1) issue there
is a CLIP on acetic anhydride in which boric acid is described
as a mild oxidizing agent. I do not question that heating
a mixture of acetic anhydride and boric acid is a hazardous
operation, but I do strongly question whether boric acid is
an oxidizing agent of any kind, mild or otherwise.
If boric acid is an oxidizing agent in this or any reaction,
it must then be reduced. What are the products of
the reduction of boric acid?
No oxidation or reduction occurs in the reaction at all.
The violent reaction is caused by the avidity of acetic
anhydride for water. Acetic anhydride reacted with boric acid to
form acetic acid and boric oxide (boric anhydride). A quick
look at the heats of formation of the components will show
that there is plenty of energy available.
This may be considered a mere quibble, but I have
been involved in a situation in which ferric oxide was labeled
a strong oxidizer, due to the thermite reaction with
aluminum metal. Our HazMat people (all nonchemists)
insisted that ferric oxide must be labeled, stored, and handled
with the same precautions as nitric acid, peroxide, etc. We
do not want boric acid to be treated by (e.g.) HazMat as
an oxidizing agent. (These same people thought that boric
acid belonged with hydrochloric, phosphoric, and
sulfuric acids.)
Literature Cited
1. Young, J. A. J.
Chem. Educ. 2001,
78, 1176.
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