Chemistry Reference
In-Depth Information
bromide and silver chloride, the determination of bromide in the presence of chloride is
not as accurate as the determination of other pairs of halides.
Hara and Okazaki [169] have described a method for the two point Gran titration of
chloride in non saline water using a silver sulphide ion selective electrode. The analysis
was performed without sample pretreatment and results correlated well with those
obtained by potentiometry and spectrophotometry or ion chromatography. Interferences
and the detection limit were examined, and the effects of temperature and number of
titration points. The Monte Carlo simulation method was used to determine the precision
of the method; two titration points were sufficient to obtain maximal precision of 0.2%
provided that the potential difference between them exceeded 20mV. The two point Gran
titration procedure was used to analyse stream and lake water with an error of less than
2% and compared with the usual seven point Gran titration method.
Levy [170] has described a titrimetric procedure for the determination of chloride ions
in the presence of free chlorine. Previous workers have attempted to remove free chlorine
by boiling the sample. This however leads to partial decomposition of hypochlorous acid
to hydrochloric acid and oxygen:
Table 2.7
Results of inter-laboratory bias tests
Std soln 46.0mg Cl L
−1
Lab
Analytical
method
River Water A
River Water B
Mean
cocn
found
a
(mg
Cl
L
−1
)
Deviation
from true
value (%)
Max
possible
bias (%)
Mean
concn
found
a
(mg
CIL
−1
)
Deviation
from
mean
value (%)
Max
possible
bias (%)
Mean
concn
found
a
(mg
CIL
−1
)
Deviati
fro
me
value (
1
Mohr titration
46.0
±0.09
0.0
±0.2
97.9
±0.17
+1.4
+1.6
8.52
±0.17
−
2
Mohr titration
45.0
±0.26
−2.2 −2.7
97.4
±0.49
+0.9
+1.4
8.28
±0.13
−
3
Mercuric
nitrate
titration
46.0
±0.41
0.0
±0.9
97.0
±0.25
+0.5
+0.8
8.80
±0.23
+
4
Mercuric
nitrate
titration
45.9
±0.13
−0.2 −0.5
96.7
±0.19
+0.2
+0.4
8.39
±0.11
−
5
AutoAnalyzer
48.0
±0.89
+4.3
+6.3
94.6
±1.03
−2.0 −3.0
8.90
±0.40
+
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