Chemistry Reference
In-Depth Information
steel wire was immersed in the solution downstream of the electrode pair and also
connected to the chassis ground point. Without these connections the signal was noisy.
The use of mercury(I) chloride electrodes for determining chloride concentrations can
be extended from the levels attainable by manual analysis to very low levels (less than
20µg L
−1
) by housing the electrode in a flow cell at a controlled temperature. At a given
temperature, the electrode is about 10 times more sensitive than the silver chloride
electrode.
One advantage of this greater sensitivity is that the mercury(I) chloride electrode does
not need to be operated at sub-ambient temperatures in order to obtain adequate precision
in the concentration range 1-20µg L
−1
. Two kinds of electrode can be used, that
developed at CERL and the Ionel SL01. The two electrodes are almost equally sensitive
and precise, but the Ionel has a faster response time and requires no preparation.
11.2.1.4
Ion chromatography
Roberts
et al.
[17] have described a method for the determniation of chloride in boiler
feed water. The application of this technique is also discussed under multianion analysis
in section 12.10.1.
11.2.2
Nitrite
11.2.2.1
Ion chromatography
The application of this technique is discussed under multianion analysis in section
12.10.1.
11.2.3
Phosphate
11.2.3.1
Ion chromatography
Stevens and Turkelson [18] have described a procedure for the determination of down to
1mg L
−1
of phosphate in boiler blow down water. The application of this technique is
also discussed under multianion analysis in section 12.10.2.
11.2.4
Silicate
11.2.4.1
Spectrophotometric method
Spectrophotometric methods have been described for the determination of traces of
silicate in high pressure boiler feed water [4,18] and deionised water [6]. Silicomolybdate
procedures employing 4-amino-3-hydroxynaphthalene-1-sulphonic acid have been
employed [4,18]. Spectrophotometric evaluation of the reduced complex is carried out at
805-810nm in these methods.
It is essential, in order to avoid silica contamination, to use precleaned polyethylene
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