McBain, James William (1882–1953)

Canadian physical chemist whose main researches were concerned with colloidal solutions, particularly soap solutions.

McBain was born in Chatham, New Brunswick, and studied at the University of Toronto and briefly in Germany at Leipzig. From 1906 he worked in the UK at the University of Bristol, becoming professor 1919. In 1926, he went to the USA to become professor at Stanford, California.

As early as 1910 he showed that aqueous solutions of soaps such as sodium palmitate are good electrolytic conductors. He postulated the existence of a highly mobile carrier of negative electricity – the ‘association ion’ or ‘ionic micelle’.

To determine the thermodynamic properties of soap solutions, he developed his own method based on the lowering of the dew point.

McBain proved that the surface phase in simple solutions is not just one monolayer thick: oriented underlayers exist beneath the monolayers of soap, and he devised an ingenious apparatus for determining their composition.

In the adsorption of gases and vapours by solids, various processes can take place simultaneously: physical sorption, chemisorption, and permeation of the solid by the gas or vapour. McBain introduced the generalized term ‘sorption’ to include all such cases. The McBain–Bakr spring balance provides a continuous record of the quantities and rate of sorption.