Determination Of the total hardness of water
Theory: Water Hardness is a traditional measure of the capacity of water to precipitate soap.
In fresh water, the principal hardness causing ions are calcium & magnesium with precipitate soap.
Total hardness is defined as the sum of the calcium & magnesium concentration, both expressed as CaCO3, in mg/l.
Soft Water 0-75mg/l
Medium Water 75-150mg/l
Hard water 150-300mg/l
Very Hard Water >300mg/l
Principle: EDTA (Ethiline Diemine Tetra Acitate) & sodium salts forms a geletanious soluble complex when added to a solution of a certain metallic cations.
If a some amount of Chrome Black T is added to sample at pH=10, it will give wine red colour with magnesium & calcium salts.
If EDTA is added, it reacts with calcium & magnesium from dry complex.
The solution will turn from wine red to blue colour.
This is the end point of the titrarion.
Apparatus Required: Burette, Burette Stand, Pipette, Two Conical Flasks, Measuring Cylinder, Standard N/50 EDTA Solution, Eriochrome Black T indicator, Ammonia Buffer( to raise pH of water to about 10)
Procedure:
1. Take 100ml of water sample in a conical flask.
2. Add 1ml of Ammonia buffer to flask.
3. Add 6 drops of Eriochrome Black T indicator to flask. Wine Red colour will be developed.
4. Titrate it with standard EDTA solution till the colour changes from wine red to blue.
Calculations:
Hardness in mg/l as CaCO3=
(ml of EDTA used x N/50 x 50 x 1000)/ ml of water sample
Result: The hardness of the given water sample is found to be _____mg/l.
Theory: Water Hardness is a traditional measure of the capacity of water to precipitate soap.
In fresh water, the principal hardness causing ions are calcium & magnesium with precipitate soap.
Total hardness is defined as the sum of the calcium & magnesium concentration, both expressed as CaCO3, in mg/l.
Soft Water 0-75mg/l
Medium Water 75-150mg/l
Hard water 150-300mg/l
Very Hard Water >300mg/l
Principle: EDTA (Ethiline Diemine Tetra Acitate) & sodium salts forms a geletanious soluble complex when added to a solution of a certain metallic cations.
If a some amount of Chrome Black T is added to sample at pH=10, it will give wine red colour with magnesium & calcium salts.
If EDTA is added, it reacts with calcium & magnesium from dry complex.
The solution will turn from wine red to blue colour.
This is the end point of the titrarion.
Apparatus Required: Burette, Burette Stand, Pipette, Two Conical Flasks, Measuring Cylinder, Standard N/50 EDTA Solution, Eriochrome Black T indicator, Ammonia Buffer( to raise pH of water to about 10)
Procedure:
1. Take 100ml of water sample in a conical flask.
2. Add 1ml of Ammonia buffer to flask.
3. Add 6 drops of Eriochrome Black T indicator to flask. Wine Red colour will be developed.
4. Titrate it with standard EDTA solution till the colour changes from wine red to blue.
Calculations:
Hardness in mg/l as CaCO3=
(ml of EDTA used x N/50 x 50 x 1000)/ ml of water sample
Result: The hardness of the given water sample is found to be _____mg/l.
2 comments
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ReplyThe experiment uses EDTA to determine water hardness as CaCO3, with color change from wine red to blue as the endpoint. visit for tanker lorry water supply in chennai anna nagar
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