‘Soap Volume’ Method

• 1. Measure out fixed volume a water sample to a boiling tube and add measured 1cm^3 of soap solution.
• 2. Put a bung in the top of the boiling tube and shake the mixture vigorously for 5 seconds.
• 3. If a long-lasting larger forms, stop adding soap solution. If lather doesn’t form, keep adding 1cm^3 portions of soap solution until a long-lasting lather forms.
• 4. Record the volume of soap solution needed to form the long-lasting lather and repeat steps for other water samples.
• 5. Compare soap solution for each sample - sample with the largest soap solution volume is the hardest sample of water.