Abstract: Chemical sensors whose active element exhibits both a visual change in color and a measurable change in electrical resistance when exposed to an analyte to which it selectively reacts are provided. These sensor have several unique features including vastly improved stability measured in years, irreversible visual changes and surprisingly reversible electrical changes. The combined unique features enable a new generation of ultra low power alerting, alarming and readout devices for hydrazines and other strongly reducing chemicals.

Abstract: Chemical sensors whose active element exhibits both a visual change in color and a measurable change in electrical resistance when exposed to an analyte to which it selectively reacts are provided. These sensor have several unique features including vastly improved stability measured in years, irreversible visual changes and surprisingly reversible electrical changes. The combined unique features enable a new generation of ultra low power alerting, alarming and readout devices for hydrazines and other strongly reducing chemicals.

Abstract: A system for detecting organic contaminants in water supplies. A sampling unit is employed which includes a housing having at least one opening therein and a tubular member positioned within the housing having a central passageway surrounded by a side wall. The side wall is made of a composition designed to absorb the contaminants. In use, the sampling unit is immersed in a water supply. The water supply contacts the tubular member through the opening in the housing, with any contaminants being absorbed into the side wall of the tubular member. A carrier gas is then passed through the central passageway of the tubular member. The contaminants will diffuse out of the side wall and into the central passageway where they will subsequently combine with the carrier gas, thereby yielding a gaseous product. The gaseous product is then analyzed to determine the amount and type of contaminants therein.

Abstract: In solid-state chemical sensors, such as the 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, the performance and lifetime are adversely affected by a build-up of insulating reaction product between two electrodes. To prolong the lifetime, intermittent sensor operation is achieved by applying a voltage between the sensor electrodes during only a small fraction of each measurement cycle and/or by reversing the voltage in successive measurement intervals and/or by switching the connections between additional reserve electrodes and/or by periodically exposing the sensor to chemically filtered air at regular time intervals during a major fraction of each measurement cycle. The response speed and sensitivity of the NaLa.sub.4 (SiO.sub.4).sub.