hydrogen electrode

electrode

 [e-lek´trōd]

either of two terminals of an electrically conducting system or cell; specifically, the uninsulated portion of a lead that is in direct contact with the body.

active electrode therapeutic electrode.

calomel electrode one capable of both collecting and giving up chloride ions in neutral or acidic aqueous media, consisting of mercury in contact with mercurous chloride; used as a reference electrode in pH measurements.

depolarizing electrode an electrode that has a resistance greater than that of the portion of the body enclosed in the circuit.

hydrogen electrode an electrode made by depositing platinum black on platinum and then allowing it to absorb hydrogen gas to saturation; used in determination of hydrogen ion concentration.

indifferent electrode one larger than a therapeutic electrode, dispersing electrical stimulation over a larger area.

point electrode an electrode having on one end a metallic point; used in applying current.

therapeutic electrode one smaller than an indifferent electrode, producing electrical stimulation in a concentrated area; called also active electrode.

hy·dro·gen e·lec·trode

the ultimate standard of reference in all pH determinations, limited and technically difficult to use, consisting of a piece of spongy platinum black partly immersed in a solution in a small glass tube; the tube above the solution is filled with hydrogen gas that is bubbled through the solution and absorbed by the platinum; the electrode thus measures the potential between H₂ and H⁺, the "standard" potential of which (1 atmosphere, 1 molar) is taken as zero; hence, the hydrogen electrode potential measures [H⁺] or pH.

hydrogen electrode

An electrode that absorbs and measures hydrogen gas; used as the reference for pH measurement in research laboratories.

See also: electrode