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AIM: TO ESTIMATE CALCIUM HARDNESS OF WATER PRINCIPLE: When addition of EDTA is applied to water containing both Ca & Mg, it combined with Ca first. Ca can be determined directly by EDTA when the pH is sufficiently high, Mg(OH) ₂ and the indicator is used that combines with only calcium murexide indicator give a color change from pink to purple. When all the Ca has been complexed by EDTA at pH 12 to 13 WHO(1963): 75mg/l as maximum acceptable   ISO(10500:1991): 5mg/l as maximum permissile ] REQUIREMENT:   8% NaOH solution Mururide indicator: ammonium purpurate = 0.2gm NaCl   = 100gm Std EDTA solution (0.01m) EDTA = 3.723 gm + 1000 ml D/W PROCEDURE: -           Take 25 ml of sample and dilute to 50ml by using D/W -           Add 1ml NaOH to rise the pH to 12 to 13. -           Add a pinc...

INTRODUCTION: Hardness is define as the concentration of multivalent cationas in solution originally, water hardness as understood to be a measure of the capacity of precipitate soap. Soap is chiefly precipitate by calcium & magnesium ion present in water Other polyvalent cations also may get precipitate. So, they often are in complex form frequently with organic constituents and have a role in water hardness. Total hardness     is defined as sum of calcium & magnesium concentration. Both are expressed as calcium carbonate in/l. When hardness is numerically greater then the sum of carbonate and bi-carbonate alkalinity, that amount of hardness equivalent to total alkalinity    is called carbonate hardness. The amount hardness in exams of these is called non-carbonate hardness. When the hardness remain in the range of 100, 200, 300… mg/l    depending on the lower 7 treatment to which water has been subjected According to internati...