From: "CHANDRA, Tilak" <tchandra**At_Symbol_Here**FPM.WISC.EDU>
Subject: Re: [DCHAS-L] Hydrofluoric acid
Date: April 2, 2012 10:32:59 AM EDT
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: <8EB0100E-EF2A-4260-82C9-18BAC336BE07**At_Symbol_Here**>

Hi all:

In extremely dilute solutions of H2O in the strongly acidic solvent HF, the
Bronsted base H2O will be protonated to the entity H30+, itself solvated by
HF molecules. The resulting solution will be basic relative to neutral HF
because of enhancement of the concentration of the Lewis
base F- through displacement, as a result of the protonation, of the position
of equilibrium for self-ionization of HF. However many such solutions are not
as basic as might be expected.
The Hammett function for 0.5 mole % of H2O in HF is -10.11 [l] whereas that
of a KF solution of equal strength is -9.5 111. If each H20 molecule was
protonated, the concentration of the base F- would be expected to be
identical with that from KF. With dilution of both solutes, H2O and KF, the
basicities of the two solutions approach each other, e.g. at 0.1 and 0.02
mole %, the Ho values are -10.57 and -10.87 for H2O and -10.30 and -10.79 for

Journal of Fluorine Chemistry, 25, 1984, 75-82.


Tilak Chandra, Ph.D.
Chemical Safety Specialist
Environment, Health and Safety
University of Wisconsin-Madison
30 East Campus Mall
Madison, WI 53715
Ph. 608-890-0255
FAX 608-262-6767

-----Original Message-----
From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of
Secretary, ACS Division of Chemical Health and Safety
Sent: Sunday, April 01, 2012 9:39 AM
Subject: [DCHAS-L] Hydrofluoric acid

From: Ernest Lippert
Subject: Hydrofluoric acid
Date: March 31, 2012 10:30:09 PM EDT

With reference to the Case report on hydrofluoric acid (HF) vapor facial
exposure (Journal of Chemical Health & Safety, January/February 2012; Sie´we´,
et al., p 7) the first sentence of the Introduction is incorrect.
Hydrofluoric acid is not "one of the strongest inorganic acids". It is, in
fact, a weak acid. See any good basic chemistry text such as Chemistry, J.
McMurry and R.C. Fay, Prentice Hall, ISBN 0-13-737776-2, p. 590-591, 1998.

The sentence would better be stated as "Hydrofluoric acid (HF), although a
weak acid, is the most tissue-destructive of the inorganic acids, and ..."

Ernest L. Lippert

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