A Passive Badge Dosimeter for HCL Detection and Measurement - SBIR 90.I (A90-189)

The research conducted during this phase I SBIR project involved a thorough evaluation of the use of dye indicator molecules to provide a colorimetric detection of gas phase HCl molecules. A wise range of acid-base indicators, incorporated into a variety of physical i.e., potential badge type configurations were employed. These physical configurations included dye indicator incorporation into encapsulated micron sized liquid crystal droplets adsorption on silica the surface of thin film chromatography strips using a solvent evaporation procedure. Nine different acid-base dye indicators were selected on the basis of their pK sub a values using indicators having values of 7.0. Samples of the various dye encoded materials described above were tested in our qualitative in nature in that they involved exposure of the dye indicator samples to vapors from solutions of varying concentration of hydrochloric acid. With the exception of the microencapsulated samples, all of the samples changed color when exposed to sufficiently high concentrations of HCl vapor. In general, detector sensitivity correlated with indicator pK sub a approx. 7.0. The microencapsulated dyeliquid crystal droplets exhibited no color changes even on exposure to vapors from concentrated HCl solutions.