At the end of their final year medical students had to write a thesis and defend it in front of their professors before they were awarded an M.D. Black undertook a comprehensive study of the chemical properties of 'magnesia alba' (magnesium carbonate) and discovered that it always lost the same proportion of its weight on heating, giving off an invisible, tasteless, odourless gas that extinguished a lighted taper, unlike air. The idea that there were gases that could be distinguished by their physical and chemical properties in the same way as liquids and solids was entirely new and was the beginning of gas chemistry. Hydrogen, oxygen and nitrogen were soon discovered by other chemists.
Presented to the University by Professor A Crum Brown.