Saturated solution of $\mathrm{KNO}_{3}$ is used to make 'salt-bridge' because
Saturated solution of $\mathrm{KNO}_{3}$ is used to make 'salt-bridge' because
velocity of $\mathrm{K}^{+}$ is greater than that of $\mathrm{NO}_{3}^{-}$
velocity of $\mathrm{NO}_{3}^{-}$ is greater than that of $\mathrm{K}^{+}$
velocity of both $\mathrm{K}^{+}$ and $\mathrm{NO}_{3}^{-}$are nearly the same
$\mathrm{KNO}_{3}$ is highly soluble in water
Solution
For a good salt bridge, the velocities of ions should be same. If the velocities are not same, then the ions would not be able to neutralize the charge equally in both half cells. Consequently, an opposite force would be developed that restricts the flow of current. For $\mathrm{KNO}_{3}$, the velocities of $\mathrm{K}^{+}$and $\mathrm{NO}_{3}$ - are nearly same. Therefore, it is used to make salt bridges.
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