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p Alkalinity and m Alkalinity

What is p Alkalinity?
  • The  term  p  Alkalinity  stands  for  “Phenolphthalein  –  Alkalinity”. 
  •  It  is  the  measurement  of Hydroxide and carbonate ion amount. 
  • It is determined by titrating a water sample with an acid of a known concentration in the presence of phenolphthalein as the indicator.
 What is m Alkalinity?
  • The  total  measurement  of  Hydroxide  bicarbonate  and  carbonate  ions amount is given by m Alkalinity. The letter m refers to Methyl orange.
  • It is the indicator that is used to determine the total alkalinity given by the above hydroxide and carbonate species.
  • When methyl orange is added, it gives its color change only  in its pH range which is, 3.1  –  4.4. Since only  trace  concentrations  of  other  acids  are  dissolved  in  water  except  for  carbonic  acid,  m Alkalinity can be considered as the total alkalinity because it gives the total carbonate alkalinity.
What is the difference between p Alkalinity and m Alkalinity?

p Alkalinity vs m Alkalinity
  • p alkalinity is the measurement of alkalinity given by hydroxide ions and half of the carbonate alkalinity.
  • m alkalinity is the measurement of alkalinity given by hydroxide ions and total carbonate alkalinity.
Indicator
  • Phenolphthalein indicator is used to determine p alkalinity.
  • Methyl orange is used to determine m alkalinity.
pH Range
  • p alkalinity is measured at a range of 8.3 –10.0 pH.
  • m alkalinity is measured at a pH range of 3.1 – 4.4.

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