Patent GB-1340084-A (GB)
Title: Solid electrolyte cells
IPC: G01N27/406
Filed: 1970-12-31
Abstract: 1340084 Electro-chemical analysis KOMBINAT MESS-UND REGELUNGSTECHNIK DESSAU VEB 31 Dec 1970 61952/70 Heading GIN In a gas analysis system using a solid electrolyte cell a scale corresponding to the gas to be analysed is selected and mounted on the recorder and the system is calibrated either by using a gas of known constitution or a constant voltage cell. The electrolyte cell output is fed via a high input impedance convertor and potentiometer to a current recorder. For detecting free oxygen the appropriate scale, examples of which are shown is selected and fixed to the recorder. Then keeping the cell at some constant temperature in the range of operation of the cell and with an air reference gas a gas of known concentration, e.g. pure oxygen, is flowed through the cell. The potentiometer is then adjusted to adjust the recorder indicator to a mark on the scale corresponding to the known gas composition. After calibration the gas to be analysed is passed through the cell which is maintained at the same constant temperature. If the gas to be analysed is at a partial pressure less than in air, an air reference electrode is used and the polarity of the cell is reversed during calibration. When the gas to be analysed contains free oxygen and also oxygen in equilibrium with other gas components then the cell is operated at a fixed known temperature which is marked on the selected scale. In this case calibration is done by switching in a standard Western cell to the impedance convertor instead of the solid electrolyte cell and adjusting the potentiometer to bring the recorder indicator to a mark on the scale representative of the standard cell voltage. The zero-value of the recorder may be altered using an auxiliary voltage source and potentiometer which is calibrated by shorting out the main potentiometer, to adjust the recorder indicator to a mark on the scale. The temperature of the solid electrolyte cell may be measured using thermocouples and indicated on appropriate scales on the recorder. In order to analyse an inert gas mixture comprising oxygen, hydrogen and carbon monoxide and water and carbon dioxide a four electrode solid electrolyte cell is used. The inert gas  mixture, pure inert gas, and inert gas charged with water vapour are applied to a respective one of three of the electrodes and air is applied to a common reference electrode, the temperature of the cell being kept constant at the temperature at which the dissociation constants of water vapour and carbon dioxide are equal. The respective voltages from the cells may be applied via a respective impedance convertor and a potentiometer to a common recorder provided with a triple scale. Alternatively three separate recorders may be used. Solid electrolyte cell constructions. The solid electrolyte cell may be in the form of a tube which is mounted at each end in a respective metal socket. One of the sockets may be in two parts which screw together with a sealant ring therebetween. A flexible gas conduit is sealed to one part so that gas flows through the centre thereof and into the elctrolyte tube passing through the centre of the second part. The tube may be mounted at its opposite end in an annular metal socket and sealed therein by a plastics material, a flexible gas conduit also being sealed to the socket. If flue gases are to be analysed one of the metal sockets carrying the solid electrolyte cell is mounted via a flange to the wall of the flue gas containing vessel. The flue gas is drawn through a coarse filter and pipe inthe vessel across the face of the socket provided with a fine filter so that only a minor part of the flue gas passes into the cell. Alternatively the socket may be mounted directly on a pipe carrying flue gas and the pipe and coarse filter omitted.