Total Hardness(CaCO3)

October 13, 2016 11:30 am

Total hardness is the hardness caused due to the presence of calcium & magnesium ions present in the water.

Definition

Total Hardness test is defined as the sum of Calcium Hardness & Magnesium Hardness in the given sample. The calcium & magnesium hardness is the concentration of calcium & magnesium ions expressed as equivalent of calcium carbonate (CaCO3) in mg/L.

Range

Implications

Exposure to hard water can worsen eczema in small children.

Hardness changes the taste of water.

Hard water along with soap can increase metal or salt deposition on skin & clothes. This can result in skin irritation.

Hardness in water can cause scale deposition in water systems. Also, it can corrode the metal surfaces & pipes which reduces the lifespan of the appliance (eg. water heater).

Analysis Procedure

1. Pipette out 20 ml of sample in a conical flask
2. Add 2 ml of ammonia buffer
3. Add 2 drops of EBT indicator
4. Fill the burette with EDTA
5. Titrate the contents in the conical flask against EDTA solution
6. Continue the titration till the colour changes to dark blue
7. Calculate the Total Hardness

Calculation

Total Hardness (mg/L) = Volume of EDTA (B.R) X N X 50 X 1000 / mL of sample

Conclusion

Selection of most appropriate technology for water treatment will depend upon the quality of water. Hence, degree of hardness in water is an important factor for economic & operational considerations.

Disclaimer

The details given are for general understanding. References should be taken from respective authorized agencies.