标准电极电势Standard electrode potential

把待测半电池与标准氢电极（铂黑电极浸在 1 mol dm⁻³ H⁺ 中，通入 100 kPa H₂）用盐桥连接，用高阻电压表测电动势。若半电池中没有固体金属（如 Fe³⁺/Fe²⁺），用铂作惰性电极。实际中常以甘汞电极等作参比电极。

Connect the half-cell to a standard hydrogen electrode (platinised platinum in 1 mol dm⁻³ H⁺ with H₂ at 100 kPa) through a salt bridge and measure the e.m.f. with a high-resistance voltmeter. If the half-cell has no solid metal, such as Fe³⁺/Fe²⁺, platinum serves as an inert electrode. In practice reference electrodes such as the calomel electrode are often used.

E° 越正，氧化型越容易被还原，是越强的氧化剂；E° 越负，还原型是越强的还原剂。电池电动势 E°cell = E°(正极) − E°(负极)，E°cell > 0 的反应在标准状态下可自发进行。浓度改变时用能斯特方程计算实际电势。

The more positive E°, the more easily the oxidised form is reduced and the stronger it is as an oxidising agent; the more negative, the stronger the reduced form as a reducing agent. E°cell = E°(positive) − E°(negative), and reactions with E°cell > 0 are feasible under standard conditions. The Nernst equation gives potentials at other concentrations.