Procedure:

 

• Pipette 10 ± 0.1 ml of the supplied milk (choose at least two from three samples provided: sterilised milk, UHT milk and pasteurised milk) into two white porcelain basins. This will help observe the colour change.

 

• Add 1.0 ml of the phenolphthalein indicator into each of the porcelain basin and mix thoroughly by stirring with magnetic stirrer.

 

• Rapidly, and with constant stirring, add the 0.1 M sodium hydroxide from a burette until a faint pink colour remains for at least 10 s. Note the volume of alkalis used and repeat the titration. The time for the titration should not exceed 30 s for each sample and the results should agree within 0.05 ml.

 

• Repeat the titration and calculations with the second milk sample.