Skip to main content

Alternate Reagents for the Amperometric Analysis of Residual Chlorine I. Background and Theory

Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

Amperometric measurement of residual chlorine is widely practiced, especially for the continuous monitoring and control of the chlorination process. Developed more than fifty years ago, the technique has evolved somewhat, but the recommended practice is quite similar regardless of the instrumentation used. Most often a reagent is added, the principal purpose of which is to reduce the sample pH to below about 5, ostensibly to have the free chlorine in the HOCl form to assure an accurate measurement. The most common reagent used is an acetate buffer; alternatively, a phosphate buffer, acetic acid or CO2 has been used to lower the sample pH.

Whereas the lowering of the sample pH to below 5 does permit accurate monitoring of free chlorine residuals, the reagents used have drawbacks. Most are nutrients that can facilitate the growth of microorganisms which can clog lines and portals in the monitors, and which can be a disposal problem if an adequate drain is not available. While CO2 is not a nutrient, its limited solubility and slow dissolution so limit its pH-reducing capability, especially in buffered waters, that its use often proves unsatisfactory. Cost and maintenance requirements are also concerns with all commonly used alternatives.

A re-examination of the theory of amperometric chlorine measurement has resulted in the recognition that it is not necessary to adjust the sample pH into the range wherein the chlorine is in the HOCl form. It is necessary to provide protons required for the electroreduction of chlorine, but these protons may be the “free” protons associated with a low pH or protons bound to a proton donor but at a higher pH. It is the availability of sufficient protons that is critical to an accurate measurement, rather than a low pH per se. The theory leading to this conclusion is reviewed and experimental confirmation is presented. The constraints on reagent selection are lessened and new selection criteria for alternative reagents for the amperometric analysis of residual chlorine are delineated.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Article Media
No Metrics

Document Type: Research Article

Publication date: 01 January 2000

More about this publication?
  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

    A subscription to the Proceedings of the Water Environment Federation includes access to most papers presented at the annual WEF Technical Exhibition and Conference (WEFTEC) and other conferences held since 2000. Subscription access begins 12 months after the event and is valid for 12 months from month of purchase. A subscription to the Proceedings of the Water Environment Federation is included in Water Environment Federation (WEF) membership.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access. Access begins 12 months after the conference or event
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Learn about the many other WEF member benefits and join today
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more