How will you distinguish between temporary hard water and permanent hard water

Distinguish between temporary hard water and permanent hard water —

1. Two unknown samples 'A' and 'B' containing temporary and permanent hard water are taken separately in a trough or beaker.
2. The water is boiled slowly, gases allowed to escape out and then the water is filtered.
3. Ordinary soap is rubbed by the hands inside each filtered sample.

Observation —

1. One sample of water 'A' lathers with soap.
2. The sample of water 'B' does not lather with soap.

Result —

1. The boiled and filtered sample 'A' which lathers is temporary hard water whose hardness is removed by boiling.
2. Sample 'B' is permanent hard water whose hardness cannot be removed by boiling.