What is the Difference Between p Alkalinity and m Alkalinity?

The difference between p alkalinity and m alkalinity lies in the measurement process and the pH indicators used for each. Here are the key differences:

• p Alkalinity: Also known as phenolphthalein alkalinity, it measures the amount of hydroxide (OH-) and half of the carbonate ion (CO3-2) concentration in a solution. p Alkalinity is determined by titrating to the phenolphthalein endpoint at pH 8.3.
• m Alkalinity: Also known as methyl orange alkalinity or total alkalinity (T), it measures the amount of hydroxide ions and total carbonate ions (CO3-2) concentration in a solution. m Alkalinity is determined by titrating to the methyl orange endpoint at pH 4.5.

In summary, p alkalinity focuses on the measurement of hydroxide and half of the carbonate ions, while m alkalinity measures the total alkalinity, including hydroxide and all carbonate ions. The pH indicators used for each, phenolphthalein for p alkalinity and methyl orange for m alkalinity, are also different.

Comparative Table: p Alkalinity vs m Alkalinity

The difference between p Alkalinity and m Alkalinity lies in the indicators used to determine them and the species of alkalinity they represent. Here is a table summarizing the key differences:

p Alkalinity, also known as phenolphthalein alkalinity, is determined by titrating a water sample to a pH of 8.3 using the phenolphthalein indicator. It measures the amount of hydroxide ions (OH-) and half of the carbonate ions (CO32-) in the solution.

m Alkalinity, also known as total alkalinity or methyl orange alkalinity, is determined by titrating a water sample to a pH of 4.5 using the methyl orange indicator. It measures the amount of hydroxide ions (OH-), carbonate ions (CO32-), and bicarbonate ions (HCO3-) in the solution.