MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Acid-base titration. Image 1 of 3. Titrations are a method of volumetric analysis, in which a volume of one reagent is added to a known volume of another reagent until an end point, in this case between pH 3.1 and 4.4. This end point can be measured by using an indicator, a substance that changes colour depending on its environment. This reaction is an acid-base titration, and the indicator used is methyl orange. The indicator is red here, showing it is in an acid. For a sequence showing the change in colour at the end point, see images A500/348-350.
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