Hach DR/700 - Page 732

81-58
PHOSPHORUS, TOTAL, continued
4. Place the flask on
a hot plate. Boil
gently for 30 minutes.
Note: Maintain the
volume near 20 mL by
adding small amounts of
demineralized water.
Do not exceed 20 mL.
Note: This is more
easily accomplished
with a "double-boiler"
technique. Place the
flask in a pan or beaker
of boiling water which
is deeper than the
solution level in the
flask, Continue boiling
for 30 minutes.
5. Cool the sample
to room temperature.
6. Add 2.0 mL of
5.0 N Sodium
Hydroxide Solution.
Swirl to mix.
Note: Use the 1-mL
calibrated dropper
provided.
30 minutes