Indicators from blue plants

Red cabbage - a vegetable side dish - is often referred to as blue cabbage, depending on how the vegetable is cooked. How can the same substance have different colours? What "tricks" do cooks perform here? And what reactions take place? You can answer all these questions after performing the following experiment. For comparison you carry out the same examinations with a blue pansy flower.


1.     Cut up the cabbage leaf and the petals separately into the smallest possible pieces.

2.     Place the materials into two separate ampoules and fill each with water to a height of 2-3 cm.  Label the vials accordingly.                                              (More see below)


3     Put the stoppers loosely on the ampoules and heat them over the candle burner to boiling. Let them boil for a short time.                                                             4.     Transfer into each of two lines of the blister pack in the same order some drops of vinegar, lemon juice, solution of baking soda and lime water. Label the wells accordingly.

5.  Add a drop or two of "cabbage juice" in the upper row from a pipette (RO) .
Add a drop or two of "pansy juice" to each of the samples in the bottom row from the second pipette (ST).


First publication: 2008                                                          Last modification: 12.06.2014