From Big Medical Encyclopedia


a kind of an oxidation-reduction electrode, potential to-rogo is defined by balance of a redox system quinone — hydrochinone; in connection with a calomel electrode forms a galvanic cell, in size e. of page to-rogo can be judged pH of solution to within 0,03 — 0,05.

Represents a smooth platinum plate, submersed in the studied solution saturated with quinhydrone — equimolar mix of quinone (0C6H40) and hydrochinone (H0C6H40H). In water solution there is a reaction:

HOC6H4OH 0C6H40 + 2H + + 2yo.

In acid solutions potential is X. aa. linearly depends on pH of solution; for measurement of pH in alkaline solutions >(pH 8) it is unsuitable. X. aa. more and more seldom apply in analytical and a wedge, practice since in many parameters significantly concedes to a glass electrode (see).

See also Hydrogen ion exponent. Bibliography: Bate with River. Definitions of pH, the Theory and practice, the lane with English, page 221, L., 1968. G. A. Kurella.