Sodium Thiosulphate solution
Light sensor & datalogger
Clamps and stands
Add 10ml of the Sodium Thiosulphate solution to the boiling tube and place in the water bath set to 25 degrees C.
Add 5ml of the acid to a test tube and also place this in the water bath.
Set up a clamp and stand to hold the boiling tube with the LED torch on one side of it and the light sensor on the other. Set the datalogger to measure light intensity vs time.
When both liquids are at the correct temperature take them out of the water bath, fix the boiling tube into the clamp stand between the torch and the sensor, so that the sensor is against the tube and the light shines through the liquid then tip in the acid.
When the light intensity measured stops changing stop the datalogger.
Repeat the experiment using temperatures of 30, 35, 40, 45 and 50 degrees C.
Be careful when clamping the boiling tube so that it does not get crushed. Clear up spills straight away. Goggles should be work when pouring liquids.