Alkalinity of water and its importance

What is the alkalinity of water?
From a chemical point of view, the alkalinity of water indicates the amount of its capacity to be neutralized by acid. Neutralization of water means that the pH of the water reaches about 4.5.
The alkalinity of natural waters is due to the presence of hydroxides, carbonates and bicarbonates. Of course, other ions such as phosphates, silicates and borates can also cause alkalinity, but due to their very low concentration compared to the first series ions, the alkalinity caused by them can be ignored.
Methods of measuring the alkalinity of water (alkalinity)
a) Simple alkalinity or alkalinity relative to phenolphthalein (Pa):
This alkalinity includes anions that are titrated at a pH higher than 3.8 by a standard acid and in the presence of phenolphthalein reagent.
b) Total alkalinity or alkalinity relative to methyl orange (M):
This total alkalinity includes anions that are titrated at a pH higher than 3.4 by a standard acid and in the presence of methyl orange reagent.
Importance of alkalinity
Alkalinity is a factor affecting the corrosion and sedimentation of water. For example, it can be said that the alkalinity of water used in steam boilers must be high enough to prevent corrosion of the boiler walls. Also, alkalinity should not be so high that it causes solids to be transported by steam or causes alkali embrittlement and cracks in the boiler walls.
Relationship between alkalinity and pH
Alkalinity is closely related to pH, such that the higher the simple alkalinity (Pa), the higher the concentration of hydroxides and carbonates, so the higher the pH and the more alkaline the solution becomes.
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