Abstract: A method of introducing selectivity to a non-selective gas sensor for determining an amount of a gas of interest contained in a measurement gas wherein the non-selective gas sensor responds not only to the gas of interest but also to other interfering gases contained in the measurement gas, the method includes the steps of periodically modulating a specified flux of a measurement gas at a first predetermined frequency, periodically modulating a specified flux of a gas of interest at a second predetermined frequency, adding the modulated flux of the gas of interest to the modulated flux of the measurement gas, exposing a non-selective gas sensor to the combination of the modulated flux of the measurement gas and the modulated flux of the gas of interest, measuring a sensor output of the non-selective gas sensor at zero frequency (DC) and at specified frequencies (AC), and determining an original concentration of the gas of interest in the measurement gas from the measured sensor output at zero frequency and at

Abstract: A method for determining an amount of a gas of interest contained in a measurement gas includes the steps of periodically modulating a specified flux of a measurement gas at a first predetermined frequency, periodically modulating a specified flux of a specified gas that can react non-linearly with the gas of interest at a second predetermined frequency, adding the modulated flux of the specified gas to the modulated flux of the measurement gas, passing the mixture of the two modulated gas fluxes through a reactor where the gas of interest reacts with the specified gas to produce a third gas, exposing a gas sensor that can respond to the third gas present in the gas mixture after the reactor, measuring the sensor output at zero frequency (DC) and at specified frequencies (AC), and determining the original concentration of the gas of interest in the measurement gas from the measured sensor output at zero frequency and at the specified frequencies.

Abstract: A cutting and scraping tool has a molded, one piece body having a first portion to be held by one hand of the user and an integral blade receiving and holding portion. The blade receiving portion has a first wall which is thinner than the first portion and establishes a shoulder at the junction of the two portions. The first wall has an extension at one end which includes a section of approximately the size and shape of the first wall and a flexible connecting web enabling the section to become a second wall when folded against the first wall then to define a blade holding slit the bottom of which is the shoulder and which is dimensioned to accommodate a blade with one edge exposed. One end of the slit is closed by the web and the other ends of the walls are releasably connected to permit blade placement and removal. A blade within the slit is held against movement by bosses on one wall passing through openings in the blade and into sockets in the other wall.

Abstract: A method of selectively sensing the quantity of methane gas in an oxygen containing gas stream, which method, as taught in one of its preferred embodiment, includes the step of providing a platinum catalyst (12) and a palladium catalyst (14). The platinum and the palladium catalysts are electrically interconnected (16--16) so as to obtain an electrical output reading (24) therefrom. The electrically interconnected catalysts are heated to a temperature in a range of 350.degree.-450.degree. C. whereby a reference electrical output reading is obtained therefrom. A gas stream containing suspected methane is passed over the electrically interconnected catalysts. Methane gas contained in the gas stream is oxidized only by the palladium catalyst while all other oxidizable components of the gas stream are oxidized by both catalysts.

Abstract: Ablation of single crystal alkaline earth metal halides as barium fluoride is accomplished by contacting them with monovalent acid in fluid medium. Smooth etched surfaces are obtained by hydrogen halide as hydrochloric acid in aqueous solution acting on single crystal barium fluoride.