SOME ASPECTS OF 
Tee, PHYSICAL “CHEMISTRY, OF 
| INTERFACES. 
ADDRESS TO SECTION B (CHEMISTRY) BY 
Proressor F. G. DONNAN, C.B.E., F.RB.5., 
PRESIDENT OF THE SECTION. 
Ir was at the last meeting at Liverpool, in 1896, that I first had the 
honour of attending a gathering of the British Association. On that 
occasion Dr. Ludwig Mond, F.R.S., was President of Section B, and 
I shall never forget the interest and pleasure I felt in listening to the 
Address of that great master of science and scientific method. Little 
did I dream that in 1923 I should have the honour and privilege of 
occupying the Chair of Section B at Liverpool. 
Looking back on the Liverpool Meeting of 1896, one can say now that 
it came at the dawn of a new era in the development of physico-chemical 
science. The X-rays had just been discovered by Roéntgen. Perrin 
had proved experimentally (1895) that a negative electric charge was 
associated with the cathode rays and had surmised that these so-called 
‘rays’ were constituted by electricity in motion, thus corroborating 
Crookes’ brilliant views of a decade earlier and demonstrating that 
Lenard was wrong. Sir J. J. Thomson had just begun that splendid 
series of researches which resulted not only in the complete elucidation 
of the nature of the cathode ‘rays,’ but also in the discovery of the 
negative electron as a constant, universal, and fundamental constituent 
of all matter. 
The discovery of the chemically inert elementary gases by Rayleigh 
~ and Ramsay had begun in 1894, and the series of investigations which 
finally led to the recognition of the radio-active transformations of atoms 
and to the discovery of the nature and constitution of the atom itself, 
were just beginning. During the last twenty-five years the influence 
of these discoveries on chemical science has been enormous. ‘There 
has come about a fresh reunion of physics and chemistry, somewhat 
analogous to that which occurred in the days of Volta and Davy. During 
the two decades preceding 1896, physical science had been largely con- 
cerned with the phenomena of the ‘ ether,’ with electric and magnetic 
fields, electromagnetic waves, and the identification of light and other 
