Hach DR/700 Procedures Manual page 216

POTASSIUM, continued
13.
Place the
prepared sample in
the cell holder.
Note: Typical indoor
lighting permits the
DR/700 to operate with
the cell compartment
cover open. In bright
light, it may be
necessary to close the
cell compartment cover.
Transfer 10 mL of the
prepared sample to a
10-mL cell. If the 10-
mL cell is used for the
treated standard,
another 10-mL cell must
be used for the prepared
sample.
CALIBRATION
A new calibration is needed for each new lot of Potassium 3 Reagent
Powder Pillows. A new calibration is also needed when the expected
potassium concentration of the water sample to be tested is not between
the standards last used to calibrate the DR/700.
To perform a calibration, make 2 potassium standards. Make them so
that one has somewhat less potassium and the other somewhat more
potassium than the expected potassium concentration of the water
sample. Make each as described in step 5 of the potassium procedure.
Continue by doing steps 2 and 6 through 10, processing both standards
like the displayed standard.
Next, perform paragraph 3.2.4.1, Calibration Using Two Prepared
Standards, in the DR/700 Instrument Manual. Either standard can be
14.
Within 7
minutes after the 3-
minute period, press:
READ
The display will
count down to 0.
Then the display will
show the results in
mg/L potassium (K).
Note: Clean the cells
with soap and a brush
after use.
45-44