Hach DR/850, Procedures Manual, Page: 223 / 460

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Large interferences are caused by some biocides used in cooling
tower samples. Hach recommends testing the ternary complex
procedure on molybdenum standards containing the specific
biocides in use to determine if the ternary complex method will
work with these samples.
After many samples have been analyzed, the sample cells may
show a slight blue color. Rinse with Hydrochloric Acid Solution,
1:1, to eliminate the build-up.
Summary of Method
The ternary complex method for molybdenum determination is a
method in which molybdate molybdenum reacts with an indicator
and sensitizing agent to give a stable blue complex.
REQUIRED REAGENTS
Molybdenum Reagent Set, 20 mL sample (100 tests) ..................................................24494-00
Includes: (1) 23524-49, (1) 23525-12
Quantity Required
Description Per Test Unit Cat. No.
Molybdenum 1 Reagent for 20 mL sample size ............1 pillow ............100/pkg .......23524-49
Molybdenum 2 Reagent Solution................................... 0.5 mL .... .50 mL MDB .......23525-12
REQUIRED APPARATUS
Cylinder, mixing, graduated, 25 mL ................................... 1........................each .........1896-40
Sample Cell, 10-20-25 mL, w/cap ...................................... 2......................6/pkg .......24019-06
OPTIONAL REAGENTS
Hydrochloric Acid Solution, 1:1, 6.0 N ................................................... 500 mL ...........884-49
Molybdenum Standard Solution, Ampule
75 mg/L Mo
6+
, 2 mL ..............................................................................20/pkg .......25575-20
Molybdenum Standard Solution, 10 mg/L Mo
6+
..................................... 100 mL .......14187-42
Sodium Hydroxide Standard Solution, 1.0 N................................. 100 mL MDB .........1045-32
Water, deionized ...............................................................................................4 L ...........272-56
MOLYBDENUM, MOLYBDATE, LR,
continued