Chemistry Reference
In-Depth Information
removal of calcium and magnesium by ion exchange is critical since these ions cause a
premature indicator change. At least ten samples can be analysed per h with results
comparable to, or better than, those obtained with the conventional turbidimetric
procedure. The procedure is not affected by phosphate,
Table 6.5
Sulphate analysis for standard addition study
Sulphate
added
(mg
L
−1
)
Sulphate
found
(mg
L
−1
)
Dilution
1:x
Recovery
(%)
Sulphate
added
Sulphate
found
(mg
L
−1
)
Dilution
1:x
(mg
L
−1
)
Recovery
(%)
0
a
217
c
162
5
100.6
378
5
100.0
327
c
217
392
5
103.4
487
8.33
99.8
327
b
487
8.33
99.8
434
c
596
10
100.2
434
579
10
97.3
545
c
704
10
99.7
653
c
545
719
10
101.8
813
12
99.8
635
819
10
102.9
a
Turbidimetric analysis gives 171 mg L
−1
;
b
turbidimetric analysts gives 460mg L
−1
;
c
these
samples were treated with Dowex 50-X8 before addition of Na
2
SO
4
Source: Reproduced with permission from Elsevier Science [29]
chloride, nitrate and fluoride in amounts up to 200mg L
−1
, although these anions can
result in slightly different indicator colours.
6.3.6
Sulphide
6.3.6.1
Ion selective electrode
The application of this technique is discussed under multianion analysis in section
14.11.1.1.
6.4
Borehole waters
6.4.1
Iodide
6.4.1.1
Spectrophotometric method
In a further method [30] for determining iodide in borehole water, iodide is precipitated
with nitron in sulphuric acid medium. The extinction of a dichlorethane extract of the
reaction mixture is then measured. There is no interference from chloride or sulphate or
from bromide if sufficient aqueous chlorine is added, and nitrate interferes only in so far
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