Edible Indicators

 

Summary:  The anthocyanin in cabbage is used to demonstrate pH differences in household chemicals.

Hazards: 

Chemicals and Solutions: 

Materials: 

Purple Cabbage. (other fruits & vegetables which work well are radishes, beets, blueberries, grape juice. NOTE: Purple cabbage offers a wide range of colors and is probably the best example if a single indicator is to be used)

Beakers /cylinders

blender

array of buffers pH 2-13

household items: vinegar, aspirin, baking powder, ammonia

Procedure: 

To make cabbage indicator simply place several cabbage leaves in a blender, add water and puree.

Add indicator to each cylinder in the array of buffers.

The pH of household chemicals can be tested by adding indicator and comparing the color produced to the buffer array.

Note: The indicators tend to deteriorate on standing and should be either freshly prepared or refrigerated if necessary for a day or two. I have frozen them in ice cube trays and they have kept well for several weeks.  The indicator is an anthocyanin.

Hint: 

Discussion: 

For cabbage:

pH1-3                       pink                              7-up, vinegar, aspirin,lemon juice

pH4-7                       purple                           tap water

pH8                           blue                              soap

pH9                           blue green

pH10                         green                            sodium bicarbonate, Rolaids

pH11                         green-yellow

pH12 & up                yellow                           ammonia, drano

To schedule a demonstration, please send an email to the demonstration lab.

 

Contact:

Eric Camp

Lecture Demonstration Technician

Bagley Hall 171

(206) 543-1606

ericcamp@uw.edu

 

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