The alkalinity of water is a measure of its capacity to neutralize acids. It is primarily due to salts of weak acids,
although weak or strong bases may also contribute. Alkalinity is usually imparted by bicarbonate, carbonate and
hydroxide. It is measured volumetrically by titration with 0.02 N sulphuric acid and is reported in terms of CaCO3
equivalent. For samples whose initial pH is above 8.3, the titration is conducted in two steps. In the first step, the
titration is conducted until the pH is lowered to 8.2, the point at which phenolphthalein indicator turns from pink to
colourless. This value corresponds to the points for conversion of carbonate to bicarbonate ion. The second phase
of titration is conducted until the pH is lowered to 4.5, corresponds to methyl orange end point, which corresponds
to the equivalence points for the conversion of bicarbonate ion to carbonic acid.