\[t_+ = \frac{I_+}{I} = \frac{u_+}{u_+ + u_-} = \frac{\nu_+\lambda_+}{\Lambda_m},\qquad t_+ + t_- = 1\]
含义Meaning
某种离子所迁移的电量占总电量的分数，取决于离子迁移率。用希托夫法或界面移动法测定，可把电导率分解为各离子的贡献。
The fraction of current carried by an ion, set by its mobility; measured by the Hittorf or moving-boundary method, it splits conductance into ionic contributions.
符号说明Symbols
| 符号Symbol | 含义 Meaning | 单位 Unit |
|---|---|---|
| \(u_\pm\) | 离子电迁移率ionic mobility | m²·V⁻¹·s⁻¹ |
| \(\lambda_\pm\) | 离子摩尔电导率ionic molar conductivity | S·m²·mol⁻¹ |
推导Derivation
离子漂移速度 \(v = uE\)，所以各离子承载的电流 ∝ 浓度 × 电荷 × 迁移率。
Drift velocity v = uE, so current ∝ c z u.
对 1:1 电解质，\(t_+ = u_+/(u_+ + u_-)\)。
For a 1:1 salt t₊ = u₊/(u₊ + u₋).
离子摩尔电导 \(\lambda = zFu\)。
λ = zFu.
适用条件与局限Assumptions & limitations
迁移数随浓度略变；溶剂化离子的有效大小影响迁移率。
Varies slightly with concentration.
例题Worked example
KCl 中 t(K⁺) ≈ 0.49，接近 0.5，所以 KCl 盐桥可减小液接电势；HCl 中 t(H⁺) ≈ 0.82。
In KCl t(K⁺) ≈ 0.49, hence its use in salt bridges; in HCl t(H⁺) ≈ 0.82.