Abstract: An electrode unit for use in an analyzer of blood and of liquids includes a cylindrical outer housing having open ends and a pair of top hat end plate bushings each having a central bore and a plug portion, the bushings being positioned in each end of the housing with the plug portion directed into the housing to form a filling chamber with the inner surface of the housing. A sodium glass capillary tube is mounted in the bores of the bushings. An annular groove is formed in an end flange portion of each bushing so that a connecting alignment ring may seat in the bushing annular grooves of two adjacent electrode units to center the electrode units.