LaMotte ALKALINITY TEST KIT DR-A - Manual (Page 3)

CAL CU LA TION OF AL KA LIN ITY RE LA TION SHIPS
Results obtained from Phenolphthalein and Total Alkalinity
determinations offer a means for the stoichiometric classification of
three principal forms of Alkalinity present in many water supplies.
Classification attributes the entire alkalinity to bicarbonate, silica,
phosphoric and boric acids. This classification system further assumes
incompatilibity of Hydroxide and Bicarbonate Alkalinities in the same
sample. Since calculations are on a stoichiometric basis, ion
concentrations in the strictest sense are not represented in the results.
According to this scheme:
A.
Carbonate Alkalinity is present when Phenolphthalein is not zero
but is less than the Total Alkalinity.
B. Hydroxide Alkalinity is present if Phenolphthalein Alkalinity is
more than one-half the Total Alkalinity.
C. Bicarbonate Alkalinity is present if Phenolphthalein Alkalinity is
less than one-half the Total Alkalinity.
Mathematical conversion of the result is shown in the following table:
Re la tion ships Be tween Phenolphthalein,
To tal, Car bon ate, Bi car bon ate and Hy drox ide Al ka lin ity
Re sult of
Ti tra tion
Hy drox ide
Al ka lin ity as
CaCO
3
Carbonate
Alkalinity as
CaCO
3
Bicarbonate
Alkalinity as
CaCO
3
P = 0 0 0 T
P < ½T 0 2P T - 2P
P = ½T 0 2P 0
P > ½T 2P - T 2(T - P) 0
P = T T 0 0