Extracts
(up) / 1, 3, 5 after adding acids / 2 and 4 after adding alkalis
W18 Extracting dye from blue Petunia petalsThis experiment
requires adult supervision
Usually red cabbage is used to extract
plant indicators. For microscale science experiments
blue Petunia petals have advantages: You need only smallest quantities, Petunia
can be easily dries. So they are available all the year. Material
Tray,
electric water cooker, scissors, broad ampoule (5 ml), pipette, blister from 10
tablets, tiny
piece of an apple, dropper bottles labelled petunia extract,
water, lime water, vinegar, citric acid, washing soda. Experiment
1. Cut a blue petunia petal (fresh
oder withered) (Photo
1) into
pieces, transfer them into the ampoule.
2. Add boiling water. Wait for cooling.
3. Transfer the extract from
the ampoule to the dropper bottle. Use the pipette
4. Add 10 drops of petunia extract to each of the 10 blisters.
5. The 5 blisters in the upper row
leave as standards.
6. Add to the 5 blisters below the standards: Drops of solutions:.... Lemon (1),
washing soda (2), lime water (4) and vinegar (5), tiny piece of crushed apple
(Photo
3).
Observations a) Photo
2:
Dried pieces float on the surface.
b) The blue dye sinks to the bottom.
c) Finally a blue solution can be decanted by the pipette. Explanation Anthocyan dye in the cells of the petals is extracted by water. The
solution of the dye has a higher density than water has.
Anthocyans are indicators:
By changes of their colour they indicate whether a solution is acidic, neutral
or alkaline. back.......
go on..............first
publication: 2006 .....................................last
modification: 21.12.2008
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