Abstract: An FTIR (Fourier transformation infrared) spectrometer is disclosed, wherein a validation/calibration of the spectrometer can be carried out in cyclically recurring intervals. Using at least two temporarily available gases, a reference spectrum with a zero gas and an absorption spectrum with a calibration gas are recorded. Substitute gases can be used during validation of the spectrometer as gas components, the substitute gases simulating actual measured gas components with respect to metrological properties.

Abstract: An apparatus for measuring the total content of organic carbon (TOC) and nitrogen (TN) in water. The TOC value is correctly determined as the sum of the liquid, dissolved, and solid substances of a specimen of the water. The apparatus includes a NDIR gas analyzer for simultaneously measuring the concentration of CO.sub.2 and NO gas components with a phase separator, a thermal reactor, a condenser, and two amplifiers for the pneumatic signals of the receivers with an indicator for the measured TOC and TN concentrations. The specimen is split into a gaseous part and a liquid part in the phase separator. The gaseous part which essentially contains the inorganic fraction of carbon, the TIC fraction, in the form of CO.sub.2 gas is cooled in a condenser until a substantial fraction of its water vapor content is separated in the condenser by condensation. The dried gaseous part is directed via the comparison vessels as comparison gas.

Abstract: The invention relates to a method for determining the concentration of gases in a mixture of gasses by means of a gas sensor composed of three electrodes 1,2,3 and a solid electrolyte 4 upon the surface of which are secured the electrodes. A voltage Us being composed of a dc component Udc and an ac component Uac is applied to at least two electrodes, the measuring electrode 1 and the counter electrode 2. Us is controlled with reference to the reference electrode 3. The voltage components Udc and Uac of the voltage Us are chosen so that the metal salt formed by the ions of the solid electrolyte 4 with the gaseous components to be detected is again decomposed. The ion, current flowing between the electrodes is measured in dependence upon the voltage as applied. The concentration of the several gasses can be determined by known mathematical methods from the functional relation between the ion current and the voltage Us.