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Computation of iodine species concentrations in waterDuring an evaluation of the use of iodine as a water disinfectant and the development of methods for measuring various iodine species in water onboard Space Freedom, it became necessary to compute the concentration of the various species based on equilibrium principles alone. Of particular concern was the case when various amounts of iodine, iodide, strong acid, and strong base are added to water. Such solutions can be used to evaluate the performance of various monitoring methods being considered. The authors of this paper present an overview of aqueous iodine chemistry, a set of nonlinear equations which can be used to model the above case, and a computer program for solving this system of equations using the Newton-Raphson method. The program was validated by comparing results over a range of concentrations and pH values with those previously presented by Gottardi for a given pH. Use of this program indicated that there are multiple roots to many cases and selecting an appropriate initial guess is important. Comparison of program results with laboratory results for the case when only iodine is added to water indicates the program gives high pH values for the iodine concentrations normally used for water disinfection. Extending the model to include the effects of iodate formation results in the computer pH values being closer to those observed, but the model with iodate does not agree well for the case in which base is added in addition to iodine to raise the pH. Potential explanations include failure to obtain equilibrium conditions in the lab, inaccuracies in published values for the equilibrium constants, and inadequate model of iodine chemistry and/or the lack of adequate analytical methods for measuring the various iodine species in water.
Document ID
Document Type
Conference Paper
Schultz, John R.
(Krug Life Sciences, Inc. Houston, TX., United States)
Mudgett, Paul D.
(Krug Life Sciences, Inc. Houston, TX., United States)
Flanagan, David T.
(Krug Life Sciences, Inc. Houston, TX., United States)
Sauer, Richard L.
(NASA Lyndon B. Johnson Space Center Houston, TX, United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1994
Publication Information
Publication: Seventh Annual Workshop on Space Operations Applications and Research (SOAR 1993), Volume 2
Subject Category
Man/System Technology And Life Support
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.

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