It involves the standardization of copper sulphate solution. This is same as done in the previous activity.

1)  Pipette accurately 5 ml of Solution A and Solution B in conical flask of 250 ml capacity.

2)  Heat this mixture to boiling on an asbestos gauge and add standard invert sugar solution from the burette about 1 ml less than the expected volume which will reduce the Fehling solution of say, 48 ml.

3)  Add 1 ml methylene blue indicator.

4)  Carry out the titration and complete it within 3 minutes.

5)  The change in blue  to reddish brown colour due to  cuprous oxide formation is taken as the end point.

6)  From the volume of the invert sugar solution used, the strength of CuSO₄ is calculated by multiplying  the titrated value with 0.001 (mg / ml of the standard invert sugar solution). This is known as Fehling factor.