Hach DR/850 Procedures Manual page 443

VOLATILE ACIDS,
17.
Press:
ZERO
The cursor will move to
the right, then the
display will show:
0 mg/L HOAc
Note: If Reagent Blank
Correction is on, the
display may flash "limit".
See Section 1.
Sampling and Storage
Accuracy Check
continued
18.
Place the prepared
sample into the cell
holder. Tightly cover the
sample cell with the
instrument cap.
Collect samples in plastic or glass bottles. Analyze samples as
soon as possible after collection. Samples can be stored up to 24
hours by cooling to 4 °C (39 °F) or below. Warm to room
temperature before testing.
Standard Additions Method
a) Snap the neck off a Volatile Acids PourRite Ampule
Standard Solution, 62,500 mg/L as acetic acid.
b) Use the TenSette Pipet to add 0.1, 0.2, and 0.3 mL of
standard, respectively, to three 25-mL graduated mixing
cylinders, each containing 25 mL of filtered sample.
Stopper. Shake well to mix.
c) Remove a 0.5 mL aliquot of sample from each cylinder;
add to three dry sample cells. Analyze all three samples
along with the original test sample beginning with Step 5
of the procedure. The volatile acid concentration should
increase 250 mg/L volatile acids as acetic acid for each 0.1
mL of standard added.
d) If these increases do not occur, see Standard Additions in
Section 1.
19.
Press:
READ
The cursor will move to
the right, then the result
in mg/L Volatile Acids
as acetic acid will
be displayed.
443