I’ve already briefly mentioned that I was doing work on heavy water and logs of phosphoric acid, sulphuric acid and so forth. Another theme that I thought of, which you will understand was very much related to the periodic table, is that boron is the lightest element in group three – or group 13 in the modern nomenclature of the periodic table. Next below that is aluminium and I’ve already mentioned that aluminium chloride and Friedel–Crafts catalysts were important components in my thinking a couple of years earlier. Boron, aluminium... gallium comes next, then indium and thallium. Very little chemistry was known about gallium, indium and thallium in the 1950s so I thought that would be an interesting field to develop.

I started with gallium, which is a very important element, in fact, for a variety of reasons. The first one is that it was discovered in, I think, 1875 by Lecoq de Boisbaudran who owned, or his family owned some of the best vineyards in the Cognac region so he was not short of money. He chose to use it by being an independent scientist; he was interested in spectroscopy; he discovered gallium.