MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Methyl orange. In an alkali and acid titration methyl orange is used as an indicator. Above pH 4.4 methyl orange is yellow, but as acid is added it turns orange. As excess acid is added and the solution goes below pH 3.1, it turns red. The process can be reversed by adding alkali until the solution returns to pH 3.47, its point of neutrality. Methyl orange has a sharp end point.
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