1. to assemble and operate a paper chromatography apparatus
2. to study the meanilng and significance of Rf values
3. to test various food colorings and to calculate their Rf values
4. to compare measured Rf values with standard Rf values
5. to separate mixtures of food colorings into their components
6. to identify the components of mixtures by means of their Rf values
Supplies
Equipment Chemical Reagents
per class: set of food coloring
5 glass stirring rods (yellow, green, blue, red)
several pairs of scissors unkown mixture of food colorings
per lab station:
3 large test tubes(25 mm x 200 mm)
3 Erlenmeyer flasks (250 mL)
metric ruler
pencil
chromatography paper strips
(2.5 cm wide x 66 cm long)
Procedure
Part I: Setting Up
1. Get 3 Erlenmeyer flasks and put a test tube in each one.
2. Get 3 chromatography paper and draw a line across each strip 4cm from one end then cut a point from the end.
3. Put water on test tubes, about 2cm deep
Part II: Rf Values of Individual Food Colorings
1. You get to test one food coloring to test. Get one of your chromatography paper and place a dot of food coloring on the line.
2. Put the strip in the test tube. Don't push the strip down too far, tip should just touch the bottom. Don't let the strip touch the wall of the test tube.
3. Observe.
4. Continue observing for 10 min. Try to identify 2 colors as they move up the paper.
5. After about 20 minute and there's no more color separating, immediately draw a line across the top edge of the water before it evaporates.
6. Measure d1 and d2 then record the values on tables 1 and 2. Then calculate the Rf value.
Part III: Separation of Mixtures into Their Components
1. Second strip will be spotted with a sample of green coloring and the third will be spotted with an unknown mixture of food coloring.
2. Follow directions from part II from 2-6.
3. Record data on Table 3
4. Clean up.
Table 1 : Results for Lab Station
Table 2 : Class Results
Table III
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