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Re: proper pH
>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
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.