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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