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Plug the 12 VCD adapter into the power supply socket.Press the button "R" so that the absorbance value is 0.00 and transmittance value is 100%. 3. Remove the cuvette containing the reference sample and place another cuvette containing the CuSO4 solution of known concentration into the colorimeter. Press the button "T" and record the value of absorbance displayed on the LCD screen in the Table 1.Plot a graph of absorbance (Y-axis) versus the concentration of CuSO4 solution (X- axis).Mark the aborbance value of solution X on the X-axis and draw a horizontal line which meets the calibration curve.2.4.5.6.7.

Plug the 12 VCD adapter into the power supply socket.
2. Switch on the colorimeter and fix the wavelength at 680nm. Fill the cuvette with the
reference sample (distilled water) and place it in the colorimeter. Press the button “R”
so that the absorbance value is 0.00 and transmittance value is 100%.
3. Remove the cuvette containing the reference sample and place another cuvette
containing the CuSO4 solution of known concentration into the colorimeter. Press the
button “T” and record the value of absorbance displayed on the LCD screen in the
Table 1.
4. Repeat the same procedure with other solutions of CuSO4 including the solution of
unknown concentration (solution X) and record the absorbance of each solution in
Table 1.

ً 5. 6. 7. Plot a graph of absorbance (Y-axis) versus the concentration of CuSO4 solution (X-
axis). The graph will be a straight line and is called the calibration curve.
Mark the aborbance value of solution X on the X-axis and draw a horizontal line which
meets the calibration curve. Now draw a vertical line from this point to meet the X-
axis. The point where this vertical line meets the X-axis gives the value of “X”
(unknown concentration of CuSO4).
The concentration of the solution X can thus be calculated.