Notes On Individual Methods - Swann Chematest 35 Operator's Manual

Chematest 35
Photometry
4.3.
Free chlorine
and cyanuric
acid
Combined
chlorine
Ozone
14

Notes on Individual Methods

When free chlorine is determined in the presence of cyanuric acid,
two forms of chlorine are measured: free chlorine and chlorine
bound to cyanuric acid. To determine the disinfection capacity of
the water, the concentration of cyanuric acid must also be mea-
sured and the result of the chlorine determination must be correct-
ed as follows:
Cyanuric acid
Percentage of free
chlorine in the mea-
sured value
The method catalogue of the Chematest 35 contains two options
for measuring combined chlorine:
 with one cuvette or
 with two cuvettes.
Apart from the fact that one or two cuvettes are used, the two meth-
ods are identical. Measuring with only one cuvette is faster and re-
quires less reagents. However, some standards require
measurement with two cuvettes. The selection of the method
should be based on the site-specific requirements.
Ozone decomposes in a very short time and is usually only present
in traces. It is essential to rinse the cuvette three times with the
ozone-containing sample before starting the measurement. Carry
out the further steps as quickly as possible, but work meticulously.
20 mg/l 30 mg/l
50% 43%
50 mg/l 70 mg/l
26% 19%
A-96.730.121 / 160920