89th American Meteorological Society Annual Meeting

Sunday, 11 January 2009
Verification of the ratio of iodine to ozone in typical ozonesonde cathode solutions
Phoenix Convention Center
L. A. Baran, University of Wyoming, Laramie, WY; and J. L. Mercer and T. Deshler
Ozonesondes are instruments commonly used to measure ozone concentration in the atmosphere. Essentially an electrochemical cell, air is pumped into the cathode chamber where ozone reacts with a dilute solution (typically 1.0% or 0.5%) of potassium iodide, forming iodine. A current is generated as two electrons for every iodine molecule flow across the cell; this current is directly proportional to the amount of ozone entering the chamber. Theoretically, one molecule of iodine is produced for every molecule of ozone reacting in the solution. However, past studies have suggested that additional reactions, which may be due to phosphate buffers included in the KI solution, occur producing more iodine and thus causing erroneously high concentrations of ozone to be documented. The overall goal of this project is to determine, using the most widely used cathode solution strengths (1% full buffers and 0.5% half buffers), if the stoichiometry of the reaction is indeed 1:1. After exposing cathode solutions to known amounts of ozone, the iodine formed is titrated. More iodine than ozone would suggest that other reactions are occurring in the cell, and a correction factor may need to be applied to ozonesonde data to allow for accurate documentation of ozone levels. Currently, lab results have yielded less iodine than ozone. A typical lab test generated 1.2E-07 moles of ozone, with some of this ozone escaping the sensing solution (~2E-08 moles). Assuming no other ozone loss is occurring, total ozone reacting in the solution is approximately 9E-08 moles. Titrations of iodine show that approximately 4.25E-08 moles were formed during the test. This is a result that has not been documented in past work, and must be studied further. Work must be done to lessen the escaping ozone as well as determine the cause for the low amounts of iodine formation.

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