What is hardness of water? How can it be determined by using EDTA in a laboratory? In an experiment to determine the hardness, a sample 100 ml of water required 15 ml of N/50 EDTA. 100ml. of water after boiling for 15 minutes and making up to 100 ml again with distilled water, required 8 ml of EDTA for titration. Calculate total, temporary and permanent hardness of water