pH indicator

Peter Gadsby pgadsby at care6.physio-control
Tue Apr 16 13:46:39 EST 1996


In article <3172BAF2.55A4 at primenet.com>, <estherc at primenet.com> writes:
> Path: 
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> From: Esther Ceren <estherc at primenet.com>
> Newsgroups: bionet.general
> Subject: pH indicator

> I am looking for the name of the chemical/pigment that changes it's 
> color from blue to red in the presence of an acid and to green in the 
> presence of an alkali. 
> 
You are probably talking about a mixture as opposed to a single indicator.
 From the Chem Physics Handbook52nd edition page d-106

Lacmoid  changes from red to blue  at 4.4 - 6.2

m-Nitrophenol changes from colorless to yellow from 6.8 - 8.6

That should give you what you want.

Pete




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