What happens if the sample alkalinity is higher than 700 mg/l CaCO3 when a CL17 is used to measure total chlorine?

Document ID

Document ID TE9889

Published Date

Published Date 05/08/2018
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Question
What happens if the sample alkalinity is higher than 700 mg/l CaCO3 when a CL17 is used to measure total chlorine?
Summary
CL17 higher amount of CaCO3
Answer
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The free chlorine oxidizes the DPD compound indicator, this reaction can only take place if the samples pH is between 6.3-6.6.  For total chlorine potassium iodide is added to the reaction. The Chloramines oxidize iodide to iodine which along with the free Chlorine oxidizes the DPD compound this reaction only happens at a pH of 5.1.  If they pH levels are not met because the alkalinity of the solution the readings of the CL17 will be low.
 

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