What is the difference between free chlorine and total chlorine?

Document ID

Document ID TE191

Published Date

Published Date 03/05/2019
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Question
What is the difference between free chlorine and total chlorine?
Summary
Free and Total Chlorine difference
Answer
Free chlorine refers to both hypochlorous acid (HOCl) and the hypochlorite (OCl-) ion or bleach, and is commonly added to water systems for disinfection. When ammonia or organic nitrogen is also present, chloramines known as monochloramine, dichloramine, and trichloramine will quickly form. Chloramines are also known as combined chlorine. Total chlorine is the sum of free chlorine and combined chlorine. The level of total chlorine should always be greater than or equal to the level of free chlorine.

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