Determination of calcium and magnesium from irrigation water sample.

Title - of calcium and magnesium from irrigation water sample. 

Principles -

Sodium EDTA forms complex, A stronger Complex with calcium and magnesium in alkaline buffer medium of pH is 10 using EBT indicator. At the end of reaction the colour of indicator changes from wine red to blue or blueish green. 

Reagents 

1) Buffer solutions -

Add 67.5 gm pure ammonium chloride in 570 ml concentrated ammonium Hydroxide and make up the volume to 1 litre with distilled water.

2) Erichrome black T indicators. -

Weight 0.5 gram of EBT di* and 4.5 gram hydroxylamine hydrochloride(NH2oH.Hcl) and dissolved both in hundred ml of Ethylene alcohol. 

3)EDTA Solution - 0.01N 

Weight 2 gram disodium salt of EDTA and dissolved in distilled water and make up volume of 1 litre with distilled water.

4) Potassium ferrocyanide -

Dissolve 4 gram potassium ferricyanide in hundred ml distilled water. 

5) Triethanolamine -

TEA Indicator reagent grade. 

6) Hydroxylamine hydrochoride - NH2oH Hcl. -

Dissolve 5 gram hydroxylamine hydrochloride in hundred ml distilled water. 

Procedure -

1) Take 10 ml of water sample in hundred ml clean conical flask and dilute by adding about 25 ml distilled water. 

2) Add 1 ml of buffer solution to raise pH to 10. Add 10 drops each of Potassium ferrocyanide, triethanolamine , hydroxylamine hydrochloride and 4 drops of EBT indicator. It will give red colour to the solution.

3) Titrate the contain against standard EDTA (0.01 normality) till colour changes wine red to blue.

4) Note the volume of EDTA used in ml .

5)Run the blank. Simultaneously using 10 ml distilled water in place of sample use all Regent and titrate against EDTA solution. 

6) Subtract blank reading from sample reading to get through reading of sample.

Sample reading - blank reading = ml. of EDTA 

Calculation -

Formulas 

Ca²+ + mg²+ m.eq./lit.  = 

ml. of EDTA × N of EDTA × 1000

÷ ml.  of water sample 

= ml. of EDTA × 0.01 ×1000 ÷ 10

=ml. of EDTA × 1

Ca²+ mg²+ m. eq./lit. = -----'

Ca + Mg of given water sample is -------- m. eq./lit. 

 Ratings -

Ratings for calcium and magnesium. 

<1.5m.eq./lit.	Good quality water.
1.50 to 3m.eq./lit .	Medium quality water.
>3m.eq./lit.	Bad quality water.

Conclusion -

Hence given water sample is ------(ratings)