Hach DR/700 Procedures Manual page 351

ARSENIC,
22.
Place the
prepared sample in
the cell holder.
Note: Typical indoor
lighting permits the
DR/700 to operate with
the cell compartment
open. In bright
sunlight, it may be
necessary to close the
cell compartment cover.
Transfer 10 mL of the
blank and 10 mL of the
sample to a
10-mL sample cell and
proceed.
REAGENT PREPARATION
Prepare the arsenic absorber solution as follows:
1. Weigh 1.00 g of silver diethyldithiocarbamate on an analytical
balance.
2. Transfer the powder to a 200-mL volumetric flask. Dilute to volume
with pyridine. (Use pyridine only in a fume hood.)
3. Mix well to dissolve. Store the reagent, tightly sealed, in an amber
bottle. The reagent is stable for one month if stored in this manner.
Larger volumes of reagent can be prepared if the reagent is used within
one month.
CALIBRATION
Perform a new calibration for each lot of arsenic absorber solution
prepared as follows:
continued
23.
Press:
The display will
count down to 0.
Then the display will
show the results in
mg/L arsenic (As).
READ
52-25