MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Pupil performing titration. Schoolgirl dripping measured volumes of an acid from a burette (down right). The conical flask (lower right) contains a measured volume of an alkali and the indicator methyl red. As the acid & alkali mix they change the pH of the solution, resulting in a change in the indicator's colour. The yellow colour of the solution in the conical flask indicates that it has a pH above six, and is alkaline.
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