VPE 511: Environment and Environmental Hygiene (2+1)

CLASSIFICATION OF HARDNESS

• Temporary / carbonate hardness: (Carbonates of calcium and magnesium ions)
• Permanent / Non - Carbonate hardness: (Sulphates of calcium and magnesium ions).

Estimation of Total Hardness (Temporary hardness +Permanent hardness)

Aim

• To estimate the total hardness of given water sample.

Materials Required

• Burette 
• Conial Flask 
• Pipette 
• Solutions 
• EDTA Solution
  • 4 gms of distilled water 
• Ammonia Buffer
  • 16.9 gms of ammonium chloride + 14.3 ml con. NH₃OH + 1.15 gms of mercuric chloride in  250 ml of distilled water 
• Erichrome indicator
  • 1 gm of erichrome in 1000 ml of absolute alcohol.

Procedure

• The EDTA solution is taken in th burette 
• 25 ml of water sample is taken in a conical flask and 0.25 ml of ammonia buffer is added to it. 
• To that, 1 or 2 drops of erichrome indicator is added. 
• The mixture in the conical flask is titrated against EDTA in the burette. 
• End point is the appearance of blue colour.

Test Sample

S.No	Volume of Sample (ml)	Burette  Reading (ml)		Volume of EDTA Consumed (ml)
		Initial	Final
1.	25 ml water +0.25 ml ammonia buffer			V

Calculation

Total Hardness = Volume of EDTA consumed (V) x 20