The Bjerrum length (after Danish chemist Niels Bjerrum 1879–1958 ) is the separation at which the electrostatic interaction between two elementary charges is the Boltzmann constant is the absolute temperature in kelvins. This length scale arises naturally in discussions of electrostatic, electrodynamic and electrokinetic phenomena in electrolytes, polyelectrolytes and colloidal dispersions.

In standard units is the elementary charge is the relative dielectric constant is the vacuum permittivity. For water at room temperature , so that

In Gaussian units

The relative permittivity εr of water decreases so strongly with temperature that the product (εr·T) decreases. Therefore, in spite of the (1/T) relation, the Bjerrum length λB increases with temperature, as shown in the graph above.

See also

• Debye length

• Debye–Hückel equation

• Shielding effect

• Screening effect

• Electrical double layer, (EDL)

• Brownian motion

References