The equivalence point of the reaction is determined by the use of acid- base indicator. For this titration the indicator is phenolphthalein, which changes from colorless at pH = 8 to pink at pH = 10. A known mass of the acid is placed in a container (generally an Erlenmeyer flask) and dissolved in about 25.0 mL distilled water (it is not necessary to dissolve all the acid at first). Then the NaOH solution is added using a burette so that the addition can be stopped, and the volume of base measured, when the first permanent pink color appears.