Water hardness test by EDTA titration method

Water hardness determination with EDTA titration can be done as per below procedure.EDTA titration method for water hardness testing. Principle, calculations, reagents edta titration procedure for water hardness testing. Total water hardness.

 

METHOD      :-          Titrimetric method.


PRINCIPLE  :-          EDTA form chelated soluble complex when added to a solution of Certain metal cations. If small amount of Eriochrome Balck is added to an aqueous solution containing Ca and Mg ions at pH 10 + 0.1, the solution becomes wine red. After titrating with EDTA Ca and Mg will be complex the solution turns from wine red to blue.
 
REAGENTS :-          1) Buffer Solution :-
Dissolve 1.179 EDTA and 780mg of
Magnesium Sulphate ( MgSO₄.7H₂O) in 50ml distilled water
Add this solution to 16.9gm NH₄Cl and 143ml conc. NH₄Cl
with mixing and dilute to 250 ml with distilled water.

• 01 M EDTA Solution :-

3.723 gm of EDTA in 1000ml Distilled Water.

• Eriochrome Black T :-

0.5 gm of dye i.e. Eriochrome Black T + 100 gm of Sodium chloride => grind to fine powder . This will serve as an indicator.


PROCEDURE:-       Take 50ml sample + 1 ml buffer solution to give pH 10.0 +
A pinch of Eriochrome Black T indicator. Titrate with 0.01M EDTA. End point is wine red to blue.


CALCULATION:-                                                                            A x B x 1000
Hardness as CaCO₃mg/l =                                                        -------------------------------
                                                                                                            ml of sample


A         =          Burette reading.
B         =          mg of CaCO₃ equivalent to 1 ml of EDTA.