LaMotte AUXILIARY PHOSPHORUS TEST KIT APT - Manual (Page 3)

of the boiling step. Do not allow the sample to go to dryness or to
dense white sulfur trioxide fumes. Remove from heat and cool.
4. Add one drop of *Phenolphthalein Indicator, 1% (2246) to the
cooled sample.
5. While swirling flask, use a 1 mL pipet (0354) to add *Sodium
Hydroxide, 15% (7886) dropwise until the solution turns faint pink.
A volume of slightly less than 3 mL is required.
6. While swirling flask, add *Sulfuric Acid, 36% (7885), one drop at a
time, until pink color disappears.
7. Quantitatively transfer the sample, which should be at room
temperature, to the 50 mL graduated cylinder (0418). After
transferring the solution from the flask to the graduated cylinder,
wash the flask with a little Deionized Water (5115PT) and add to the
solution in the graduated cylinder. Now dilute exactly to 50 mL using
Deionized Water (5115PT) and mix well.
8. Test the solution, from Step 7, for orthophosphate according to the
procedure given for the particular test outfit being used. This is
Reading B. Reading B represents hydrolyzable phosphorus
(polyphosphates) and orthophosphates.
Hydrolyzable Phosphorus = Reading B - Reading A
C. TOTAL PHOSPHORUS
1.
Fill 50 mL graduated cylinder (0418) to 50 mL line with filtered
water. Pour into a 125 mL Erlenmeyer flask.
2. Use a 1 mL pipet (0354) to add 1 mL of *Sulfuric Acid, 36% (7885)
to flask. Swirl to mix.
3. Use the 0.5 g spoon (0698) to add one measure of *Ammonium
Persulfate Reagent (6566). Swirl to dissolve.
4. Add a few boiling stones (7888). Place flask on hot plate and boil
gently for 30 minutes. Add Deionized Water (5115PT) to the sample
during the boiling step to maintain a volume between 10 and 50 mL.
Or microwave on high power for 2 minutes. Permit the volume to
decrease to approximately 10 mL (about c inch of water) by the end
of the boiling step but do not allow the sample to go to dryness or to
dense white sulfur trioxide fumes. Remove from heat and cool.
5. Add one drop of *Phenolphthalein Indicator, 1% (2246) to the
cooled sample.
6. While swirling flask, use a 1 mL pipet (0354) to add *Sodium
Hydroxide (7886) dropwise until the solution turns faint pink. A
volume of slightly less than 3 mL is required.
7. While swirling flask, add *Sulfuric Acid, 36% (7885), one drop at a
time, until pink color disappears.