YSI 9300 Photometer - Manual (Page 104)

PHOTOMETER TEST INSTRUCTIONS
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The Alkalinity of water is caused by the presence of alkaline substances such as
hydroxides, carbonates, bicarbonates and, to a lesser extent, silicates and
phosphates. Quantitatively alkalinity is the capacity of the water to react with
acid to a specified pH end point. The value obtained will depend on the pH
indicator used. Two measures of alkalinity are conventionally applied - Alkaphot M
(Alkalinity to methyl orange) and Alkaphot P (Alkalinity to phenolphthalein).
Alkalinity is an important test parameter in a number of industrial water uses,
notably in boiler water treatment. Boilers and steam raising plant are normally
operated under conditions of high alkalinity in order to minimise corrosion and
the monitoring of alkalinity is an important control test.
The YSI Alkaphot M and Alkaphot P tests provide a simple means of checking
Alkalinity M and Alkalinity P levels over the range 0 - 500 mg/l CaCO
3
. The tests
are particularly suited to boiler and industrial waters. The alkalinities specifically
due to carbonates, bicarbonates and hydroxides can be calculated from the
various data obtained.
Method
The YSI Alkaphot M and Alkaphot P tests are both based on unique colorimetric
methods. These methods offer considerable advantages over the titrimetric
methods traditionally used for measuring these parameters.
The tests are each based on the use of a single tablet reagent containing a
precisely standardised amount of acid combined with a color indicator. The tests
are simply carried out by adding the appropriate tablet to a sample of the water
under test. Over the alkalinity range of each test a distinctive series of colors is
produced - from yellow through green to blue in the case of the Alkaphot M test
and from colorless to purple in the case of the Alkaphot P test.
The color produced in each of the tests is indicative of the alkalinity and is
measured using a YSI Photometer.
Photometer Method
AUTOMATIC
WAVELENGTH
SELECTION
0 – 500 mg/l CaCO
3
PHOT.37.AUTO