13 COLOURED EXTRACTS FROM FLOWERS AS INDICATORS OF ACIDS AND BASES a Extract coloured substances from plants Select brightly coloured flowers such as the purple and red bougainvillaea or coloured leaves Squeeze or grind one of the coloured flowers or leaves in a mortar with a mixture made of 2 mL acetone and 2 mL ethanol By this means the colouring matter will be extracted into the solvent Filter and collect the filtrate Repeat this experiment with one or two other flower colours Keep these coloured solutions for use as indicators in the next experiment