23
23
MAGNETIC STIRRER
HI 190M
POWER
SPEED
ON
OFF
MAX
FILTERED
SOLUTION
6. Dip the sodium electrode
FC300B
into the
filtered sample. The tip of the electrode
should be immersed for approximately
2.5 cm/1" (i.e. the electrode junction must
be completely immersed) without touch-
ing the bottom of the beaker. During mea-
surement, the sample should be gently
stirred (100 rpm).
7. Wait for the reading to stabilize, i.e. no
drift for at least a couple of minutes.
Take note of the measured value.
8. Since the dilution rate is 1/10, the reading
in the g/L range has to be divided by 100
to get the actual reading of NaCl (per
gram of cheese or meat) or it can be
considered the value directly expressed in
% of NaCl.
Note
: 10 to 15 minutes as response time, in
the first measurement taken in samples
of cheese or meat, is the right amount
of time needed by the electrode to
stabilize. The next measurements in
cheese or meat samples will have a
shorter response time (less than 2 min-
utes). Do not rinse the sodium elec-
trode between measurements since con-
tamination is negligible.
mannacl_r1.P65
24
24
IONIC STRENGTH ADJUSTER (ISA)
It is recommend the use of
HI 7090
ISA solu-
tion when the NaCl concentration of the
sample is lower than 5 g/L. In such case, the
calibration of the meters should be performed
with standard solution containing 2% of ISA.
ISA
(Ionic Strength Adjuster) = 50% of NH
4
Cl 4M +50% of NH
4
OH 4M (use 2mL of ISA
every 100 mL of sample).
TEMPERATURE
The best working temperature is around 20-
25°C (68-77°F).
For greatest accuracy, we suggest to perform
the calibration of the meter with standard
solution at a temperature as close as pos-
sible to the temperature of the sample (± 1°C/
±2°F).
Na CONCENTRATION WITH HI 931100 AND
HI 931102
It is always possible to determine the Na
concentration by using the formula:
X
Na
= X
NaCl
• (23 / 58.4)
where
X
Na
= Na concentration
and
X
NaCl
= NaCl concentration
