Abstract: The invention relates to a method for determining small quantities of carbon monoxide and nitrogen oxides in gaseous mixtures containing oxygen with the aid of a sensor whose electrical resistance changes at a higher temperature with the carbon monoxide and nitrogen oxide concentrations. It makes use of the fact that, with suitable sensors, on the one hand the resistance-temperature curve of the one of the gases to be determined is clearly different from that of the reference mixture over a broad temperature range (gaseous mixture without the two gases to be determined) and, on the other hand, the resistance-temperature curves of the two gases to be determined approach one another in one part of this temperature range, or coincide, and maintain a clear distance from one another in another part of this temperature range.

Abstract: The invention relates to catalytic coating compositions for surfaces of cookers, ovens, fryers or grills, to a process for the preparation of these coating compositions, and to cookers, ovens, fryers or grills or parts thereof having surfaces provided with the coating compositions according to the invention.

Abstract: The invention relates to a sensor for the determination of carbon monoxide, especially in gas mixtures containing oxygen, on the basis of doped metal oxides whose electric conductivity is a function of the composition of the gas mixtures. Suitable metal oxides are those having n-type conductivity, the dopants used being other oxides of a metal having a maximum valency <4; oxides of a metal catalyzing the reaction of carbon monoxide with oxygen to give carbon dioxide, each in amounts from 0.01 to 0.2 mol %; and from 0.001 to 0.1 mol % of an oxide of a metal of the 5th subgroup of the Periodic Table of Elements. The sensors are notable for a small resistance-temperature coefficient while having high sensitivity and low hysteresis.

Abstract: A gas sensor device has a carrier plate of ceramic or glass. The carrier has apertures which leave only strips in a spiral configuration connecting a middle region of the carrier to the outer region thereof. The apertures may be mere slits separating the connection strips or they may be apertures providing larger air gaps. On each middle region so provided on the carrier a sensor element is located that has two electrodes and a sensitive layer which establishes a conducting connection between the electrodes. The electrodes and the sensitive layer are directly applied to the upper surface of the middle region. The two electrodes are comb shaped and are placed in inter-digital configuration to define a meandering gap between them. On the underside of the middle region of the carrier a heating element for the sensor element is provided and, if desired, also a temperature measuring resistance for regulating the temperature produced by a heating resistor.

Abstract: An ignition system comprising one of a glow plug, spark plug and glow attachment having metal or ceramic surfaces which are exposed to a fuel/air mixtuer, and are at least partially covered with a coating comprising at least one complex metal oxide obtained as a result of a reaction of a basic oxide selected from a group comprising oxides of Si, Y, La and Ce and mixed oxides of the above-mentioned oxides with Al.sub.2 O.sub.3, with at least one further oxide selected from a group comprising oxides of alkali and alkali earth metals.

Abstract: The use of zeolites rich in silicic acids having an Si:Al ratio of 1:1 to 100:1 as specific adsorbents for NO.sub.X or CO is proposed. Because of their property of specifically adsorbing NO.sub.X or CO, these zeolites, in particular those zeolites doped with such metals as Ca, Co, Ni, Fe, Cu, Ag, Pt or Ru, and having the above mentioned ratio of Si to Al, are especially suitable for the production of specific NO.sub.X or CO sensors based on semiconductors. Such sensors can be used as sensors for exhaust gases of automotive vehicles, for example.

Abstract: To detect substantial deviation of operation of the engine with fuel-air mixtures from stoichiometric relationships, particularly extended operation under very lean or enriched supply mixtures, the exhaust gases are conducted past a first sensor which provides a clearly defined voltage jump upon change of the exhaust gases between reducing and oxidizing state; and, additionally, to a second exhaust gas sensor and preferably to a third sensor, the second and third sensors being, respectively, responsive to the oxygen level in the exhaust gases and to the CO (or hydrocarbon) level in the exhaust gases, respectively, and additionally modifying the relative proportion of fuel and air of the mixture being fed to the engine.

Abstract: Tin oxide doped with magnesium oxide or niobium pentoxide and prepared as a sintered material is found to be highly sensitive to oxygen partial pressure both in the presence of free oxygen and in the presence of oxidizable gases, such as carbon monoxide or the lower oxides of nitrogen, and even in the presence of mixtures of both, such as in the exhaust gas of an internal combustion engine. The electrical conductivity varies by substantially more than an order of magnitude in response to a change in the oxygen partial pressure of about one-half an order of magnitude. The doped oxides operate as poor catalysts for the oxidation of oxidizable components of the exhaust gases. Chromium oxide doped with tin oxide shows the effect of an excessively good catalysis from the point of view of range of measurement, but is usable to give a sharp indication of the appearance or disappearance of free oxygen in a gas mixture.

Abstract: The present invention provides a catalyst for converting the noxous CO, NO.sub.x and hydrocarbons found in the exhaust gases from internal combustion engines into less harmful gases, and to the method of treating said exhaust gases. The catalyst consists essentially of a solid solution of Fe.sub.2 O.sub.3, Cr.sub.2 O.sub.3, and Fe.sub.3 O.sub.4. The catalyst may be extended on a porous carrier such as aluminum oxide or aluminum silicate. The catalyst is particularly suited for treating the exhaust gas from internal combustion engines of motor vehicles.