To Determine The Total Hardness Of Water Using EDTA Method
Hard water is genrally considered to be one which requires considerable amount of soap to produce foam or leather. Hard water cause scale formation in boilers heaters and hot water pipes.
The rain water catches CO2 from the atmosphere when the water pass through CaCO3 rock in the Soil, these compounds make the water hard.
Calcium and magnesium chlorides and sulphates also cause hardness
There are two types of hardness:
This type of hardness is mostly caused by Ca(HCO3) or Mg(HCO3) OR both, therefore it is also called carbonate hardness, these compounds dissolve in water and form Ca2, Mg+2 and HCO3 ions which cause hardness
H2O+ CO2--> H2CO3
CaCO3 + H2CO3 --> Ca(HCO3)2
Temporary hardness can be removed by Clark's method by adding limewater,Ca(OH)2 to the hard water.
Ca(HCO3)2 + Ca (OH)2 -->2CaCO3 + 2H2O
As the magnesium carbonate and calcium carbonate are insoluble in water and settles down,
It is also known as non carbonate hardness and it is caused by CaCl2.MgCl2, CaSo4 and MgSO4, the ion exchange method is used for the removal of the permanent hardness sodium zeolite is added to hard water due to which calcium or magnesium zeolite is formed which is insoluble in water.
Ca + 2Na (zeolite) --> Ca (Zeolite ) + 2Na + 2
Total hardness = (Final hardness reading - Initial reading) 1000/50.
The following values give the type of hard water:
W.H.O guideline value of hardness is 500mg/lit as CaCO3
Buffer solution of hardness ferrochrome black tea EDTA solution of 0.02normality.