5
By simply pressing
START
key, the
HI 84431
automatically starts pump operation and titrates the
sample to the end point. The
HI 84431
has a simple and accurate peristaltic pump to ensure the best
accuracy and repeatability. By performing pump calibration with the Hanna standard provided, the
instrument accuracy is assured.
The instrument employs a powerful and effective built-in algorithm to analyze the pH response to
determine the exact pH endpoint, then uses this to make the necessary calculations. The Titratable
Alkalinity determination is instantaneously displayed in selected measurement units on the large
dot matrix display. The instrument is ready for the next analysis immediately.
Other features:
• Log on demand up to 100 samples (50 for pH measurement; 50 for titration results)
• GLP feature, to view last calibration data for pH electrode and pump
MEASUREMENT SIGNIFICANCE
Water alkalinity is expression of a waters acid-neutralizing capacity and it is determined by
titration with standard acid solutions.
Alkalinity is an important parameter for control and treatment of potable and wastewaters, because
it indicates the water buffering capacity (ability to resist at pH change, primarily because of
bicarbonate/ carbonate content). A low water alkalinity signifies that the water is susceptible to pH
change and high alkalinity indicates that water is able to resist a major change of pH. Alkalinity can
be used to estimate water hardness or to determine water corrosive capacity.
Alkalinity of surface water, quantified by mg/L as CaCO
3
or meq/L, may be caused by carbonate,
bicarbonate, hydroxide, phosphates, borates, silicates or organic acids salts.
Conventionally, the water alkalinity is approximated as sum of components. Three types of alkalinities
exist together to form total alkalinity:
TA = OH
¯
+ CO
3
2
¯
+ HCO
3
¯
OH
¯
– hydroxide alkalinity
CO
3
2
¯
– carbonate alkalinity
HCO
3
¯
– bicarbonate alkalinity
TA – total alkalinity
Different tests can be performed to determine the quantity of different alkalinities present. A
titration to pH 8.3 is considered Strong Alkalinity (SA) and to pH 4.5 Total Alkalinity (TA).