Hardness, Total
Hardness, Total
Hardness_MP_ULow_CPZ_Eng_2400.fm Page 5 of 6
Summary of Method
Calcium and magnesium combine equivalently with the Chlorophosphonazo
Indicator to form a colored complex which absorbs light very strongly at 669 nm.
One drop of the CDTA reagent breaks up this complex, and the resultant
decrease in color is proportional to the amount of calcium and magnesium (as
CaCO
3
) in the sample.
Required Reagents
Quantity Required
Description Per Test Unit Cat. No.
Chlorophosphonazo Indicator Solution Pillows..................................1 ....................... 100/pkg.............25895-99
CDTA Reagent for Ultra Low Range Hardness ...................................1 drop.............. 10 mL SCDB .....25896-36
Required Apparatus
Clippers (Shears) for opening solution pillows ...................................1 ....................... each....................23694-00
Multi-pathlength Cell Adapter...............................................................1 ....................... each....................59466-00
Sample Cell, Multi-pathlength w/cap ..................................................1....................... 6/pkg.................59405-06
Required Standards
Calcium Standard Solution, 20-mg/L as CaCO
3
........................................................... 946 mL...............21246-16
Calcium Standard Solution, 0.50-mg/L as CaCO
3
........................................................ 946 mL...............20580-16
Water, Ultra-pure (aldehyde-free) .................................................................................... 500 mL...............25946-49
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