Study on Estimation of Alkalinity of Water Sample Using a Novel Technique pH-Metric Method

Abstract

The alkalinity of water is one of the important parameters of water quality. The volumetric titration method using a standardized hydrochloric acid solution is a prevalent technique to estimate individual concentrations of basic radicals, like, , , and  ions, which are primarily responsible for the alkalinity of water. However, the method needs two external indicators, namely phenolphthalein and methyl red to mark the end points of titrations. Furthermore, accuracy of the method is sacrificed due to inevitable parallax errors during marking of the end point of titration. This present work reports that during titration of a given water sample with a standardized acid solution, preferably  solution,  changes continuously. This change in  is closely monitored and recorded graphically. Sharp change in  is observed near the end point of titration and hence neutralization volume can be obtained from the corresponding curve. The nature of the  curve clearly indicates the type of basic radical/radicals present in the water sample. The neutralization volume, thus obtained, is used to calculate the individual concentration of each basic radical present in the water sample. This novel technique obviates the use of any external indicators and eliminates any possible parallax error.