Water Hardness Test Method

Last Updated on 22/12/2020

Water Hardness Test Method

Rana Sohel
Executive Engineer
Sunman Textile Mills Ltd. Chittagong
Email: rsohel07tex@gmail.com


The presence of Calcium, Magnesium salt i.e bi-carbonates, sulphates, Chloride in water is called causes of hardness of water. Such soluble salt are chloride, nitrites, sulphates and bicarbonate of these metal heavy metal like Fe and Al also can tribute in the hardness of water. It is reported as parts per million (as calcium carbonate). Moderate to high hardness water of 150–500 ppm can be partially softened by precipitation of the offending species. The water which contains these salt is called hard water. There are two types of hardness: Temporary hardness and permanent hardness. Hard water caused many problems to the textile fabric or fiber during wet processing. It also creates different problems in different stages of treatement with it. Besides scale formation on equipments, in boilers and pipelines. So before using water in wet processing treatment water hardness test should do.

Water hardness test
Fig: Water hardness testing

Water Hardness Test Method:
There are few methods for measuring water hardness. In this article I have explained three methods of measuring hardness of water.

1. Ammonia- Ammonium Chloride Buffer Solution:
Dissolve 67 gms. Ammonium Chloride to 570 ml concentrated Ammonia and then make up the solution to one Litre by distilled water.

2. Erichrome Black – T Solution:
Dissolve 75 ml Tri-ethanolamine to 25 ml Ethanol and then add 0.5 gm Erichrome Black – T in 100 ml volumetric flask.

3. 0.01M EDTA standard solution:
Dissolve 3.722 gms EDTA(Ethylene Diamine Terra Acetic Acid) to one Litre distilled water.

Testing Procedure:
Take 100 ml of Sample in a Beaker + 5 ml (NH4)Cl buffer solution + 1-2 drops of Black – T and Titrate it against EDTA (0.01M)

1 ml of 0.01 M EDTA = 1 mg.
Total Hardness= Volume of EDTA * 10 ppm.

100 ml Sample are taken. But for ppm sample will be 1 litre, so the result will be 10 times more.

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