COMPLEXOMETRY ANALYSIS (Calcium and Magnesium) BY EDTA TITRATION

 Inorganic Chemistry Practical

 

 

Aim: Determination of Calcium and Magnesium in a given  water sample by EDTA  titration.

 

Procedure:

Weight out accurately 0.367 gm. of CuCl₂^.2H₂O and 0.510 gm. of MgCl₂^.6H₂O separately and then transfer it t into 250 ml. measuring flask and dilute it exactly to 250 ml. with deionized water and shake it well.

• TO DETERMINE CALCIUM AND MAGNESIUM

Take 10 ml of the diluted solution in 150 ml.  conical flask.  Add 10  drops  buffer  solution  (pH  =  10)  and  3-4  drops  of  Eriochrome  Black T  (EBT) indicator. Titrate this solution against 0.01 M EDTA solution. At the end point color changes from wine red to blue or green.  Let this reading be X ml.  This reading represents Ca+2 and Mg+2 together. Subtract Y from X to obtain the amount of Mg+2 only.

• ESTIMATION OF CALCIUM

Take 10 ml. diluted solution in 150 ml. conical flask. Add 4-5drops of 4.0 N NaOH solution and few crystals of Muroxide  (Ammonium  Purpurate)  indicator powder.  Titrate  this  solution  against  0.01  M EDTA  using  microburette.  At the  end point colors change from orange red to lavender or purple. Note this reading be Y ml. These readings represent only Ca+2.

 

• Observation

Part:-I         Estimation of Calcium and Magnesium

•  Burette: 0.01 N EDTA
•  Pipette: Take  10 ml. given  Water  sample  + 10  drops of  buffer Solution (pH=10)
•  Indicator: EBT
• Color change: Wine red to blue

Burette Reading	Pilot ml.	Ist  ml.	IInd ml.	IIIrd ml.	Constant
Final reading					X ml.
Initial reading
Difference

• Part:-II        Estimation of Calcium
• Burette: 0.01 N EDTA
• Pipette: Take  10 ml. given  Water  sample  + 5 drops of  4N NaOH solution
• Indicator: Murexide
• Color change: Orange red to lavender or purple

 

 

Burette Reading	Pilot ml.	Ist  ml.	IInd ml.	IIIrd ml.	Constant
Final reading					Y ml.
Initial reading
Difference

 

 

Result:

 

(1)       Amount of Calcium in the given unknown solution is         ppm.

           (2)       Amount of Magnesium in the given unknown solution is         ppm.