Re: proper pH

[Bill Warner <lww at ictech_net>]

>Date: Sat, 21 Feb 1998 09:25:07 -0800 (PST)
>From: "A. Inniss" <andrewi at u_washington.edu>
>Subject: Re: proper pH
>
>	Well, yes, as "true" buffer is one that contols pH shifts in
>either direction.  I believe the term is amphiprotic?  Chemists help me!

Not quite.  An amphiprotic substance is simply a substance that can act as
either an acid or a base.  In general, amphiprotic substances by themselves
do not resist pH changes well, and are not effective as buffers.

A buffer is a solution that contains a conjugate acid-base pair.  That is,
an acid and a base in equilibrium (not a single substance), which together
act to resist pH changes.

>There was some discussion a while back about calling baking doda (sodium
>bicarb., or maore accurately sodium hydrogen carbonate) a "true" buffer.  
>Some argued that it is really more like a pH adjuster from a chemists
>perspective.

The bicarbonate ion is an amphiprotic substance, and by itself is not a
buffer.  However, in combination with a suitable concentration of carbonate
ion, or aqueous CO2, it can be one half of a buffer system.

--Bill

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