389 / 670
Into a 120 mL sample beaker or autosampler cup. Add 5 mL nitric acid solution [
D
e], and 50 mL
123
of water before titration.
124
Add a magnetic stirring rod (if the titrator does not have a build-in rod stirrer). Place the
125
autosampler cup or beaker onto a magnetic stirrer and stir until dissolved or finely suspended.
126
(e)
The pH of the test solution must be below 1.5. In case of any doubts, check by means of a
127
pH-meter and, if necessary, add a little more nitric acid solution [
D
e].
128
G. Instrument Operating Conditions
129
(
a)
Check and maintenance of the combined silver electrode
130
Rinse electrode with deionized water and wipe before use. Renew the electrolyte 1M KNO
3
(
D
i)
131
periodically
per manufacturer’s recommendations
.
132
If fat sticks to the electrodes during a series of analyses, then eliminate it by briefly immersing
133
the electrode in acetone.
134
The silver electrode must be stored in 1M KNO
3
(
D
i) after appropriate cleaning.
Note: In place
135
of the combined silver electrode, separate silver and reference electrodes may also be used.
136
(b) Titration.
137
Connect the combined silver electrode to the titration apparatus, according to the manufacturer's
138
indications. Ensure that the titration vessels are correctly placed on the autosampler and there are
139
enough reagents: both nitric acid solution (if added automatically) [
D
e] and 0.1 M AgNO
3
[
C
i].
140
If no autosampler is available, then place the sample solutions manually under the titration
141
equipment.
142
Put the wash solution [
D
f] in the washing position if an auto sampler used. Ensure that the
143
volume of wash solution is adequate.
144
2015.07/2015.08 (February 2016)
Chlor-02/Chlor-04
FOR ERP USE ONLY
DO NOT DISTRIBUTE