creator Stetter, Joseph R. creator Cao, Zhuang A highly sensitive and selective sensor for the detection of halogenated compounds comprises a bead of sodium lanthanum fluoride silicate, having the molecular formula NaLa.sub.4 (SiO.sub.4).sub.3 F, in which are embedded two noble metal electrodes, preferably a straight platinum wire near the center and a helical platinum wire near the periphery of the bead. A current passing through the helical wire maintains the sensor temperature at about 550.degree. C. by resistive heating. The electrical resistance between the two wires is deduced from measurements of the current passing through a fixed external resistor when a substantially constant voltage, preferably about 4 volts, is applied between the wires. A decrease in the measured resistance is an indication of the presence of a halogenated compound in the sample of air to which the bead is exposed. The sensor is preferably controlled by a microprocessor or microcomputer that also performs data processing. This system not only detects a halogenated compound of interest, but also measures its concentration. Submitted by Aric Ahrens (ahrens@iit.edu) on 2011-12-12T18:50:19Z No. of bitstreams: 1 5226309.pdf: 263401 bytes, checksum: 22c17659d6a89ec0265a2082049fd73b (MD5) Made available in DSpace on 2011-12-12T18:50:19Z (GMT). No. of bitstreams: 1 5226309.pdf: 263401 bytes, checksum: 22c17659d6a89ec0265a2082049fd73b (MD5) Previous issue date: 1993-07-13 Illinois Institute of Technology 2009-05-11 1993-07-13 5,226,309 http://hdl.handle.net/10560/2404 en United States Patent Patent reformatted digital application/pdf No Copyright - United States http://rightsstatements.org/page/NoC-US/1.0/ Open Access