LaMotte TOTAL & PHENOLPHTHALEIN ALKALINITY TEST KIT 4533 - Manual (Page 2)

7. Multiply number of drops used in Step 6 by 10. Add to result from
P Alkalinity procedure. Record as ppm Total Alkalinity as CaCO
3
.
ppm T Alkalinity =
(Number of drops in Step 6 x 10) + ppm P Alkalinity
If testing only Total Alkalinity, do Steps 1, 5 and 6. Multiply number of
drops used in Step 6 by 10. Record as ppm Total Alkalinity as CaCO
3
.
CAL CU LA TION OF AL KA LIN ITY RE LA TION SHIPS
The results obtained from the Phenolphthalein and Total Alkalinity
determinations offer a means for the stoichiometric classification of the
three principal forms of alkalinity present in many water supplies. The
classification attributes the entire alkalinity to bicarbonate, carbonate and
hydroxide, and attributes the absence of other weak acids of inorganic or
organic composition, such as silica, phosphoric and boric.
This classification system assumes the incompatibility of hydroxide and
bicarbonate alkalinities in the same sample. Since the 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 the phenolphthalein alkalinity is
not zero but is less than the total alkalinity.
B. Hydroxide alkalinity is present if the phenolphthalein alkalinity is
more than one-half the total alkalinity.
C. Bicarbonate slkalinity is present if the phnolphthalein alkalinity is less
than one-half the total alkalinity.
Relationships Between Phenolphthalein Alkalinity,
Total Alkalinity, Carbonate Alkalinity, & Hydroxide Alkalinity
Result
of
Titration Hydroxide
Alkalinity as
CaCO
3
Carbonate
Alkalinty as
CaCO
3
Bicarbonate
Alkalinity as
CaCO
3
P = 0 0 0 T
P < aT 0 2P T - 2P
P = aT 0 2P 0
P > aT 2P - T 2(T - P) 0
P = T T 0 0
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