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More on Determining Free Available Chlorine
Author(s) -
Johnson J. Donald
Publication year - 1983
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.1002/j.1551-8833.1983.tb05111.x
Subject(s) - chlorine , iodide , chemistry , standard error , statistics , mathematics , inorganic chemistry , organic chemistry
Writing in response to “Determining Free Available Chlorine by DPD‐Colorimetric, DPD‐Steadifac (Colorimetric), and FACTS Procedures” by Cooper et al (JOURNAL AWWA July 1982) and “Letters to the Editor” by Palin (JOURNAL AWWA March 1983), this reader states that the practical significance of a 4 percent error in monochloramine (NH2Cl) is debatable. Two situations commonly occur in which this error is much higher than 4 percent. If the concentration of NH2Cl is 2.5 mg/L and free chlorine is 0.1 mg/L, then the error chlorine measurement after 1 minute is also 0.1 mg/L or a 100 percent error in free chlorine. Of even greater significance is the error caused by a small amount of iodide coupled with the fact that the DPD method uses 10 g potassium iodide/L in the total chlorine measurement.