multi EA 5100
Sulfur analysis with the S module 5100 coulometric
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10
Sulfur analysis with the S module 5100 coulometric
10.1 Function and design
10.1.1 Function and measuring principle
Expansion of the basic module with the detection module allows the determination of
the sulfur content in solids, liquids, and gases via microcoulometric titration.
The organic sulfur compounds are incinerated into a mixture of sulfur dioxide (SO
2
) and
sulfur trioxide (SO
3
) in the basic module. Both oxides are created in a fixed relation. Car-
bon dioxide and water is also created during this incineration.
The amount of SO
2
is proportional to the total sulfur amount in the sample.
The measuring gas flow is first dried and then routed to the detection module via a
transfer line. In the measuring cell, the sulfur oxides dissolve in the electrolyte and react
with iodine. This decreases the cell potential.
R-S + O
2
→ SO
2
+ SO
3
+ CO
2
+ H
2
O
2 H
2
O + SO
2
+ I
2
→ H
2
SO
4
+ 2 HI
R: Hydrocarbon residue
After a specified accumulation time dependent of the sulfur content of the sample, titra-
tion begins. The iodine ions are oxidized back to iodine at the anode. This increases the
cell potential. The end point of the iodometric titration has been reached when the
measuring cell has again reached its original potential.
With titration and end point routine: The electrode reactions consist of an anode reac-
tion (+) and a cathode reaction (-).
Anode (+): 2 I
-
→ I
2
+ 2 e
-
Cathode (-): 2 H
+
+ 2 e
-
→ H
2
10.1.2 Design
The detection module consists of the following main components:
¡
Measuring cell with electrodes
¡
NOx and HX absorbers for gas purification
¡
Gas inlet tube
¡
Magnetic mixer
¡
Interface to the basic module
A easily-opened door for changing the electrolyte solution is installed on the front of the
detection module. For maintenance purposes, the door can be removed.
