Determination of CLORIDES from irrigation water sample.

Aim -

Determination of chloride from irrigation water simple. 

Principle -

Mohr's titration method (argentrometric) is most commonly used for chlorides determination. 

It Depend upon formation of sparingly soluble greek silver chromate (AgcrO4) precipitated at the end point. 

When sample is titrated against the standard Silver Nitrate (AgNo3) solution in presence of potassium chromate (k2crO4) as colour indicator.

Reagents -

1) potassium chromate indicator 5% solution -

Dissolved 5gm potassium chromate in about 75 distilled water and add saturated solution of silver nitrate. Dropwise until a slite permanent red precipitated is formed. Filter and dilute 100ml with distilled water .

2) standard silver nitrate (0.02 normality AgNo3) -

Dissolved 3.40 gram silver nitrate in distilled water and volume made up to 1 litre and stored in Amber colour bottle away from light. 

Procedure -

Take 10 ml of water sample in hundred ml conical flask and dilute to 25 ml with distilled water. 

Add 5 drops of K2 cr O4(potassium chromate)  indicator .

Making it dark yellow indicator.

Titrated with standard silver nitrate (0.02 normality ) solution with continuous  stirring . 

Till first brick red colour appears. 

Note the volume silver nitrate required as 'V' ml. 

Rating for chlorides. 

 

<4	Good quality water
4 to 10	Medium quality water
>10	Bad quality water.

Formula / calculation -

Chloride ( mleq/lit)  =volume of AgNo3 required × N of AgNo3 × 1000/volume of water sample. 

= V × 0.02 × 1000/10

put value of V .

Chlorides( mleq/lit)=  -------

Results 

Hence given water sample contain ---------mleq/lit chlorides. 

Conclusion -

Hence the given water sample is ---------(rating) quality water.