Optical connections: Elements of colour

The history of scientific discovery is littered with mistakes, coincidences and serendipity. In chemistry, the formulation of a periodic table by Dmitri Mendeleev, which he presented to the Russian Chemical Society in 1869, enabled the search for new elements to gather pace by predicting their presence from supposed blank spaces in the table. Yet there are still instances of elements having been discovered fortuitously and unexpectedly. The story of one such element, indium, discovered by two German chemists shortly before the publication of Mendeleev’s table has a neat optical resonance with the researches of an English chemist over 50 years previously.