250 cm3 Conical Flask & Bung
Measuring cylinder, 100cm3, 25cm3 & 10cm3.
1% Soap Solution
Sodium Carbonate Solution (0.40 mol/dm3)
1. Measure 20cm3 of hard water (containing the calcium ions) and pour it into the conical flask.
2. Measure out 80cm3 of distilled water and add it to the conical flask.
3. Add 5cm3 soap solution to the water.
4. Add 1cm3 of sodium carbonate solution (water softener), put on the bung and shake vigorously for 10 seconds.
5. Leave the flask for 20 seconds and if there is still a lather then record the volume of sodium carbonate solution added. If not add another 1cm3 of sodium carbonate solution, shake for 10 seconds and leave for another 20 seconds. Repeat this process until you have a lather and record the volume of sodium carbonate added.
6. Rinse out the flask thoroughly.
7. Now measure out 40cm3 of hard water, add it to the conical flask and add 60cm3 of water to dilute it up to 100cm3 and repeat the experiment.
8. Do this for 60cm3, 80cm3 and 100cm3 of hard water ensuring that enough distilled water is added to keep the total volume at 100cm3.
The soap solution is flammable to keep it away from naked flames.
The soapy water is very slippery so you must mop up any spills as soon as possible to avoid someone slipping over on it.