Normal carbonate is present if the alkalinity to phenolphthalein is
greater than zero but less than the alkalinity to methyl orange,
erythrosine, or lacmoid. If the phenolphthalein alkalinity is exactly
equal to one-half the methyl orange, erythrosine, or lacmoid alkalinity
the alkalinity is due entirely to normal carbonate. If the
phenolphthalein alkalinity is less than one-half the methyl orange,
erythrosine, or lacmoid alkalinity normal carbonate expressed in terms
of calcium carbonate is equal to twice the phenolphthalein alkalinity.
If the phenolphthalein alkalinity is greater than one-half the methyl
orange, erythrosine, or lacmoid alkalinity the normal carbonate is equal
to twice the difference between the methyl orange, erythrosine, or
lacmoid alkalinity and the phenolphthalein alkalinity. The carbonate,
carbon dioxide as carbonate, and bound carbon dioxide can be calculated
as follows:
Carbonate (CO_{3}) = 0.6 times the normal carbonate expressed in terms
of calcium carbonate.
Carbon dioxide as carbonate (CO_{2}) = 0.44 times the normal carbonate
expressed in terms of calcium carbonate.
Bound carbon dioxide (CO_{2}) is the sum of the carbon dioxide as
carbonate and one-half that as bicarbonate.