Hach DR/700 Procedures Manual page 394

HARDNESS,
16.
Place the third
sample cell in the cell
holder.
Note: Typical indoor
lighting permits the
DR/700 to operate with
the cell compartment
cover open. In bright
sunlight, it may be
necessary to close the
cell compartment cover.
Transfer 10 mL of the
blank solution to a 10-
mL cell. If the
10-mL cell is used for
the blank, another
10-mL cell must be used
for the sample.
STATISTICAL EVALUATION
A single operator repetitively tested samples of two laboratory prepared
solutions, using one DR/700, matched sample cells and two
representative lots of testing reagents. Testing 1.23 mg/L Mg as CaCO
and 1.875 mg/L Ca as CaCO
deviation was ±0.020 mg/L as CaCO
respectively.
Testing zero concentration samples, the limit of detection was 0.011 mg/L
Mg as CaCO and 0.100 mg/L Ca as CaCO
3
calculated as three times the standard deviation when testing zero
concentration samples (Adapted from Analytical Chemistry, 1980, 52,
2242-2249).
continued
17.
Press:
READ
The display will
count down to 0.
Then the display will
show the results in
mg/L calcium as
CaCO .
3
Note: To convert the
results to mg/L Ca,
multiply by 0.400.
Note: Hardness (mg/L)
= mg/L Ca as CaCO
plus mg/L Mg as
CaCO .
3
concentration samples, the standard
3
3
52-68
3
and ±0.033 mg/L Ca as CaCO
. The limit of detection was
3
3
,
3