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Measurement limitations (pH)
- To: Aquatic-Plants at actwin_com
- Subject: Measurement limitations (pH)
- From: Paul Sears <psears at nrn1_NRCan.gc.ca>
- Date: Mon, 17 Dec 2001 11:24:42 -0500 (EST)
- In-Reply-To: <200109110748.f8B7m2Y25156 at actwin_com> from "Aquatic Plants Digest" at Sep 11, 2001 03:48:02 AM
I mentioned some limitaions of the test kits in an earlier posting.
I should mention another. Chemical indicators are materials that
change colour as the pH changes. They do this by changing form:
HA (yellow) <-> A- (blue) + H+
This means that the indicator is itself a buffer. If your solution
to be tested is very dilute, and you add too much indicator, the
indicator will have a significant, and perhaps even dominant, effect
on the pH.
Use the minimum possible.
Paul Sears Ottawa, Canada