LaMotte AM-21 Water Pollution Detection Outfit - Manual (Page 16)

5. To cells 3 and 4, add six drops of *Sodium Hydroxide Reagent with
Metal Inhibitors (4259) and stir the contents of the cells with the
spatula.
6. To cells 3 and 4, add one Calcium Hardness Indicator Tablet (5250) to
each and stir until tablets are disintegrated or until the liquid has
developed a full red color. Cell 3 will be used as the “before” color change
standard.
7. Refill the Direct Reading Titrator with Hardness Reagent #7 and add
dropwise to cell 4, stirring the solution after each drop. Continue until
the sample color changes from red to blue. Read the test result directly
from the scale where the large ring on the Titrator meets the Titrator
barrel. Record the result as ppm Calcium Hardness.
8. Subtract the Calcium Hardness level from the Total Hardness level to
determine the Magnesium Hardness level.
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