Chemistry Reference
In-Depth Information
Evolved cyanide is determined by pyridine-barbiturate photometry or potentiometrically
with ion selective electrodes.
The initial sample (600ml) is preserved by the addition of 5ml 50% sodium hydroxide.
To remove sulphide 0.2g cadmium carbonate is added to 600ml of preserved sample and
the solution filtered. A portion of this
Table 8.17
Total cyanide values for waste water samples by high-acidity and EDTA
displacement procedures
Total cyanide found,
mg L
−1
High-acidity
procedure
EDTA displacement
procedure
Sample
nature
a
Thiocyanate
present
mg L
−1
Nitrate
present
mg
L
−1
Not
added
Added
Sulphamic acid
Not added
Added
WW H
<0.2
71
<0.02
<0.02
WW I
<0.2
97
0.02
0.01
WW J
<0.2
105
<0.02
<0.02
WW K
<0.2
173
<0.02
<0.02
WW L
1.2
90
0.37
0.07
WW M
2.0
31
0.66
<0.02
WW N
3.0
294
0.40
0.02
WW O
4.0
9
0.60
0.07
<0.02
WW P
4.2
100
1.5
0.12
WW Q
4.6
105
1.10
0.02
WW R
5
102
2.2
<0.02
WW S
5
33
1.20
0.02
WW T
6
66
3.4
0.01
WW C
6
127
2.0
0.26
0.12
0.02
WW F
9
140
2.8
0.16
<0.02
WW U
12
64
4.9
0.03
WW V
15
91
4.7
0.18
<0.02
WW W
17
139
0.8
0.02
a
WW=wastewater
Source: Reproduced with permission from the American Chemical Society [54]
sample is treated with sulphamic acid and disodium ethylene diamine tetraacetic acid,
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