Metallized‐Glass Hydrogen Electrodes

1. The properties of various combinations of silver, gold, palladium, and platinum, deposited on glass for use as hydrogen electrodes, have been studied. 2. These metals are easily plated on to glass tubing by dipping the glass into alcoholic solutions of their salts and then heating, the use of essential oils for reducing purposes being quite unnecessary. 3. A palladium deposit on glass made in this way may be used as a bright hydrogen electrode in solutions where Pd or Pt. black produces undesirable catalytic action. 4. Platinized gold on glass and platinized platinum on glass are the most satisfactory hydrogen electrodes for general work, being mechanically strong, very cheaply and easily made, rapid in action, and very reliable. 5. Electrodes containing palladium either as base film on glass or as electrolytic black, are slow in action, due to a strongly marked arrest in the time‐potential curve, but the final values obtained are quite reliable. 6. Palladinized electrodes have a remarkable capacity for retaining their hydrogen potential for long periods after the hydrogen supply is stopped. 7. Palladinized electrodes may be used without any external hydrogen supply, for rough determination of pH in well buffered solutions, by cathodic charging before use. 8. Palladium coatings direct on glass are liable to disintegrate after long use. 9. Silvered glass electrodes are not reliable for hydrogen electrode work, though they may be used as oxygen or air electrodes in alkali or as silver chloride electrodes after anodic treatment in hydrochloric acid. 10. All hydrogen electrodes require longer time for attaining equilibrium in alkali than in acid.