RICHARD MEGNA / FUNDAMENTAL PHOTOS / SCIENCE PHOTO LIBRARY RICHARD MEGNA / FUNDAMENTAL PHOTOS / SCIENCE PHOTO LIBRARY
A solution of sodium hydroxide containing an indicator, phenolphthalein. The pink colour seen is characteristic of phenolphthalein. The indicator is used to show the transition of an acid neutralisation of an alkali. The acid is added slowly from the burette seen above the flask containing a known amount of the alkali. When the indicator looses its colour, the neutralisation has taken place. With phenolphthalein, this 'end point' is reached at a pH of between 8.3 and 10.2. The amount of acid added is measured, and calculations of the neutralisation reaction may be made.
Model release not required. Property release not required.