Quantitative test for starch, using COLORIMETER
1 You are provided with boiling tubes containing 20cm3 of each of the following
concentrations of starch solution *.
0.16 0.08 0.04 0.02 0.00 gdm-3
2 To each boiling tube add 1cm3 of iodine solution *.
3 Use a yellow filter in the colorimeter throughout.
4 Place a sample of the zero concentration solution in the colorimeter and set
the % transmission to 100.
5 Place a sample of each of the other solutions in the colorimeter and read the %
transmission of each. Record the data in a table such as the one below.
6 Add 1cm3 of iodine to 20cm3 of the solution of unknown concentration.
7 Place a sample of the unknown in the colorimeter and record the %
8 Plot a calibration curve using the data from the table (step 5).
9 Use the calibration curve to determine the concentration of the unknown
Starch concentration/g dm-3 % transmission
* see CLEAPSS p1725
Specimen results: see Public folder-practical- calib curve
For more information about the principles of using a colorimeter see: Public folder-
File: starch(qu) (disc 9)
and Public folder (A level biology- practical)