Water Analysis : To Estimate Calcium Hardness of Water
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 pinch of murexide indicator.
-
Titrate immediately by slandered EDTA till pink color
changes to purple. Note down the volume of
EDTA.
-
Calculate
the amount of EDTA required by sample (C = A – B)
-
Use
the following formulae and calculate the concentration of Ca (mg/l) and Ca
hardness as CaCO₃
(mg/l)
1.
Ca
as CaCO₃
mg/l = ( C * 400.8)/ ml of Sample
2.
Ca
hardness as CaCO₃ mg/l
= ( C * 1000 * X) / ml of Sample
Comments
Post a Comment