Elektrochemische Zelle

1,127,846. Electro-chemical analysis. BECKMAN INSTRUMENTS, Inc. May 26, 1967 [July 1, 1966], No. 24500/67. Heading G1N. In a polarographic or galvanic cell for determining the oxygen content of a sample medium in which two electrodes 22, 30, Fig. 1, are immersed in an electrolyte 20, and separated from the sample by a membrane 38, e.g. of PTFE or polyethylene, permeable to the oxygen only, the thin film of the electrolyte, between the membrane 38 and electrode 22 is purged of any oxygen which would interfere in the measurements on the sample by electro-chemical or chemical scavengers provided in the cell, The electro-chemical scavengers may comprise two electrodes, the cathode 42 having the form of a cylinder surrounding but spaced from a member 18 carrying the measuring cathode 22 and the anode being formed by a wire coil 43 wound round the member 18. Either a voltage is applied between the two electrodes or they are short circuited. If the former type of system is used in a polarographic cell or the short circuited electrodes are used in a galvanic cell, the electrode 43 may be omitted, the electrode 30 being common to both cathodes, Fig. 2 (not shown). In a modification of the scavenger having short circuited electrodes, the anode may be constituted by a coating (40), Fig. 3 (not shown), covering the upper part of the cylindrical cathode (52), or a wire (56), Fig. 4 (not shown), wound round it, the two being short circuited by contact with each other. In the embodiments, the cathodes of both the galvanic cell and the galvanic scavengers are made of a noble metal, e.g. gold or silver, the anodes of a base metal e.g. zinc, cadmium or lead and the electrolyte of potassium hydroxide. For the polarographic cell and equivalent scavenger the cathodes are made of a noble metal as before but the anodes are made of silver and the electrolyte of potassium chloride. The chemical scavenger, which effects the removal of dissolved oxygen by direct chemical action may take the form of a cylinder, e.g. like the cathode 42, the coil 43 and leads being omitted, or of a wire or cylinder around the bottom of the member 18. It may be made from an active metal, e.g. magnesium, thallum, cadmium or zinc. With this scavenger the electrodes of the cell and the electrolyte depend only in the manner of operation of the cell.