Dielectric Constant

The dielectric constant (ε, Greek epsilon) is a property of a solvent. It is a measure of how well the solvent reduces interactions between ions in solution.

A dielectric constant greater than or equal to 20 means the medium is a good solvent (ie, at 20°C dH₂O has an ε ≈ 80) and an ε below that means the medium is a poor solvent (ie,at 20°C acetic acid has an ε ≈ 6).

F = [ k · q₁ · q₂ ] / [ ε · r² ]