## Principle

Total Hardness is a titration test.

The Indian Standard for drinking water holds that the acceptable limit is 200 mg/l, but in the absence of any other toxic substances or alternate source, this is relaxable upto 600 mg/l.

## Calibration

No calibration is needed for this test

## Test

• Take 25 ml of water sample in 50 ml measuring tube, add 1 ml of Total Hardness Reagent A and add one small spoon of Total Hardness Reagent B.
• A wine red color develops if hardness is present. If the solution continues to remain colourless, hardness is 0.
• Titrate the red wine color solution till turns blue, by adding drops of the Total Hardness Titrant. Keep count of the number of drops till the solution turns blue. Shake the solution on addition of each drop.
• On the app, go to `Titration Test` > `Total Hardness` and enter the number of drops.
• This should give you the result in mg/l.