Dr. Vidhin Kamble Dept. of Zoology. Sangola College, Sangola

Showing posts with label Estimation of Hardness of water. Show all posts
Showing posts with label Estimation of Hardness of water. Show all posts

02 April 2021

Estimation Of Hardness Of Water (EDTA Method) (Total, Permanent And Temporary)

 Estimation Of Total, Permanent And Temporary Hardness Of Water (EDTA Method)

Aim: To estimate the amount of total, permanent and temporary hardness in the collected sample of water.

Principle:

Hardness in water is due to the presence of dissolved salts of calcium and magnesium. It is unfit for drinking, bathing, washing and it also forms scales in boilers. Hence it is necessary to estimate the amount of hardness producing substances present in the water sample.

Hardness of water is determined by titrating with a standard solution of ethylene diamine tetraacetic acid (EDTA) which is a complexing agent. Since EDTA is insoluble in water, the disodium salt of EDTA is taken for this experiment.

Total hardness

Total hardness is due to the presence of bicarbonates, chlorides and sulphates of calcium and  magnesium ions.  .

Temporary hardness is due to the presence of bicarbonates of calcium and magnesium ions. It can be easily removed by boiling. When water is boiled, temporary hardness producing  substances (bicarbonates) are precipitated as insoluble carbonates or hydroxides. This precipitate can be removed by filtration. The permanent hardness is due to the presence of chlorides and sulphates of calcium and magnesium ions. This type of hardness cannot be removed by boiling

The total hardness of water is estimated by titrating the water sample against EDTA using Eriochrome Black-T (EBT) indicator.

Procedure:

The burette is filled with standard EDTA solution to the zero level, following usual precautions.

1.      20 Ml of the given water sample is pipette out into a clean conical flask.

2.      5 ml ammonia buffer and 2 drops of ebt indicator are added

3.      Titrated against edta

4.      From the burette.

5.      The end point is the change of colour from wine red to steel blue.

6.      The titration is repeated to get concordant titre value.

Observation table

Volume of water sample (ml)

Burette Reading

Mean CBR

Initial

Final

 

 

 

 

 

 

 

 

 

 

Calculation

Total hardness =         Mean CBR X 1000 / Volume of water sample used       

Result :

Total hardness of given water sample is  = ---------------ppm

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