 The solutions may be gels or colloids as well as solutions of electrolytes, and as such the phase boundary between gels, or a gel and a liquid, can also act as a selective barrier.The electric potential arising between two such solutions is called the Donnan potential.The effect is named after the American physicist Josiah Willard Gibbs who proposed it in 1878 and the British chemist Frederick G. Donnan who studied it experimentally in 1911.