Water Hardness is water that contains a required quantity of dissolved minerals (like calcium and magnesium) As rainwater falls, it is naturally soft.
However, after that as water flows through the ground and into various waterways,
In addition, Water picks up minerals like chalk, lime and mostly calcium and magnesium and becomes hard water. As hard water contains essential minerals, water is very essential for every human being
It is extensively useful as drinking water and various other purposes. Water usage is not only because of the health benefits, but additionally also adds to the flavour of water that is also essential.
In other words, Water that does not produce lather with soap readily is called hard water.
Therefore , the Hardness of Water is usually a measure of calcium hardness in milligrams per litre (mg/l) OR parts per million (ppm) OR in grains per gallon (GPG).
For instance : sea water, river water, spring water lake water and well water.
Water Hardness Titration method
The Hardness of Water estimate is by titration method with the chelating agent, EDTA (ethylenediaminetetraacetic acid) (Greek χηλή, chelè, meaning claw). This reagent is a weak acid that can lose four H (in bold) on complete neutralization;
The four acid oxygen sites and the two nitrogen atoms have an unshared pair of electrons,
which can form bonds with a metal ion forming a complex ion or coordination compound.
The complex that forms is quite stable, and the conditions of the formation of the complex can have an easy control and it is ready for selection for a particular metal ion.
When a titration to determine the concentration of a metal ion occurs,
Additionally, the amount of EDTA quantitatively combines with the cation to form the complex.
In conclusion ,the endpoint is reached when essentially all of the cation has reacted with the EDTA.
In this analysis a solution of EDTA will be standardized by titration against a standard solution made from calcium carbonate, CaCO3.
The EDTA solution can be used to determine the hardness of an unknown water sample.
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