W3T331759 / WT.050.585.003.UE.IM.1014
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MICRO/2000® AND DEOX/2000® MODULE
4.1.5 Total chlorine monitoring
Potassium iodide liquid reagent must be added to the analyser sample
for the measurement of total chlorine residual. The sample pH should be
maintained between 4.0 and 4.7. The iodide solution is made by adding
potassium iodide to one gallon of unchlorinated DI water.
4.1.6 Interfering residuals
Interfering residuals can cause either positive interference (strong
oxidants) or negative interference (e.g. organics that combine with
chlorine to form organic forms, some of which can behave as free chlorine
or may not be detected at all by the standard method of measurement
or by the analyser). Decreasing the analyser sample pH (e.g. from pH4
to pH2.5) may, in some applications, cause interference from oxidants
but, where acceptable, may also be desirable to improve the response to
sluggish organic chlorine compounds in the measurement of potassium
permanganate or chlorine dioxide residuals, ammonium sulphate reagent
liquid is used to eliminate the response (interference) to free chlorine when
necessary.
The MICRO 2000 Residual Analyser allows the flexibility to
select from several analyser sample conditioning chemicals (reagents).
The choice of conditioning chemical is made to provide the best analyser
performance while considering chemical cost and handling requirements.
Some applications require no chemical conditioning of the analyser
sample while others may require a combination of chemicals. Sample
conditioning may be used to provide a stable condition for residual
measurement, to eliminate interference from background residuals which
are not of interest and to chemically convert residuals to a form which
is conveniently measurable by the analyser.
Specifically, the choice of chemicals for analyser sample conditioning
in a given application is based on three parameters - the residual to be
monitored, other (potentially interfering) residuals present and water
pH and alkalinity.
Summary of Contents for WALLACE & TIERNAN DEOX/2000
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