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8. ESTIMATION OF TOTAL HARDNESS OF WATER, , Ex. No.:, , Aim, , To estimate the total hardness of the given sample of water by EDTA titration using a, , standard solution of calcium chloride of strength 0.01M., , Principle, , The total hardness of water can be determined by titrating a known volume of hard water, against EDTA solution using Eriochrome Black — T indicator. The estimation is based on the, , complexometric titration., , Date:, , , , , , , , , , , , , , Procedure, Short Procedure, DESCRIPTION TITRATION - I TITRATION - IL, Burette solution EDTA solution EDTA solution, Pipette solution Standard calcium chloride | Hard water, solution, Reagents added Ammonia buffer solution Ammonia buffer solution, Indicator Eriochrome Black — T Eriochrome Black — T, End point Change of colour from Change of colour from, wine red to steel blue wine red to steel blue, , , , , , , , , , , , Titration —I, Standardisation of EDTA solution, , The burette is washed with water, rinsed with distilled water and then with the given EDTA, solution. It is filled with same solution up to zero mark. The initial reading of the burette is noted. A, 20 mL pipette is washed with water, rinsed with distilled water and then with the given standard, calcium chloride solution. 20 mL of standard calcium chloride solution is pipetted out into a clean, conical flask. Half a test tube of ammonia buffer (10 mL) is added into the flask. A pinch of, Eriochrome Black — T indicator is added into the flask. The solution turns to wine red in colour. The, solution is titrated against EDTA solution taken in the burette. The end point of the titration is the, change of colour from wine red to steel blue. The titration is repeated to get concordant titre value., From the titre value, the molarity of EDTA solution is calculated., , 148