1928 Frederick Donnan
Collie was succeeded in 1928 by Frederick Donnan. After Graham's day, physical chemistry had been largely lost to mainland Europe, and Donnan was instrumental in restoring Britain's place in physical chemistry. He is best known for the Donnan equilibrium which refers to the diffusion of ions across a membrane in the presence of a non-diffusible ion.
He had a heavy political clout. He worked closely with the chemical industry, and as Foreign Secretary of the Royal Society he worked to bring over many Jewish refugees from Germany before the 1939-1945 war. Many of these spent a short period at University College before moving on to more permanent posts; two of these were Freundlich, of surface chemistry fame, and Edward Teller, later to be one of the fathers of the atomic bomb.