Abstract: There is described a dry chemistry test element consisting of a chemistry unit and a mount that is ammonia-sensitive, wherein the mount is improved to prevent ammonia carry-over from test element to test element. The improvement is based upon the discovery that in previous test elements which were joined together using ultrasonic bonding along energy-directing ribs, ammonia carry-over was created by the leakage of ammonia from one ammonia-sensitive element to another test element. Each element had a construction of a mount that provided a gas leakage path into the viewing aperture of the bottom sheet of the mount. The elements of the invention are provided with a smooth area on the bottom sheet which is fixed to the chemistry unit with an adhesive while the rest of the mount is joined at the energy-directing ribs.

Abstract: Nitrides and oxynitrides which can be used as selective detectors of reducing gases in the atmosphere, and a detection device containing them. Selective detectors of nitrogen-containing reducing gases in the atmosphere, in particular ammonia and gases containing NH and/or NH.sub.2 groups, of the semiconductor resistance type, the nitrides and oxynitrides according to the invention are of tetrahedral structure and contain:a metal chosen from the group comprising Li, Na, K, Be, Mg, Ca, Sr, Ba, Zn and Mn;a second element chosen from the group comprising Si, Ge, P, Al and Ga;nitrogen and, if appropriate,oxygen.

Abstract: A process for determining the composition of an aqueous solution of ammonia and carbon dioxide from which ammonium carbamate or ammonium carbonate crystallizes out upon cooling to below the saturation temperature. The density and the saturation temperature of the solution are measured, and the ammonia, carbon dioxide, and water composition is determined by reference to densities and saturation temperatures of aqueous solutions of ammonia and carbon dioxide of known composition. The composition thus determined can be used to effect control over the composition of such aqueous solutions.

Abstract: An integral multilayer analytical element for the analysis of ammonia or an ammonia forming substrate in a liquid sample is disclosed. The element comprises a transparent support on which an indicator layer for ammonia, a liquid blocking layer, a reagent layer incorporated with a reagent which may react with the substrate to form ammonia, and a spreading layer, are integrally superposed in this order. The improvement is that the liquid blocking layer is made of a porous material which is permeable to ammonia but substantially impermeable to liquids.

Abstract: A device for detecting small amounts of a chemical such as ammonia, and other ammonia-like molecules such as hydrazine or pyridine, in air and in other gases is disclosed. A capillary tube serves as a multiple total reflective medium for an optical beam from a light-emitting diode. The outer surface of the capillary tube is coated with a dye which, when exposed to the chemical, changes color so that the multiply reflected light is modified. The resultant change in the output light intensity from the capillary tube is photodetected and recorded to sense the presence of the chemical. When the chemical is removed, the dye returns to its original color so that the device can be reused.

Abstract: An ammonia gas analyzer and a sulfuric acid converter utilized in the ammonia gas analyzer in which a sample gas is maintained at a relatively high temperature prior to entering the sulfuric acid converter to thereby prevent acidic sulfuric acid sulfates and/or ammonia sulfates from crystallizing and being deposited on the walls of the device. The ammonia gas analyzer includes gas sampling means, a gas measuring channel connected to the gas sampling means, a comparison gas channel connected parallel to the measuring gas channel with the measuring gas channel including an NH.sub.3 /NO converter for converting NH.sub.3 in a sample gas into NO and means for measuring a concentration of NH.sub.3 on the basis of variations of an amount of NO in the measuring gas channel with respect to that in the comparison gas channel.

Abstract: A reaction vessel, test device, and method of detection or measurement are disclosed, featuring the use of at least two operatively connected zones formed by transport surfaces spaced apart throughout most of the zones a capillary distance. The zones are fluidly connected by meniscus control means effective to stop capillary flow of the liquid from one zone to the other, until an externally generated actuation pressure is applied.