I've just watched this marvellous lecture, given tonight at the Royal Institution. The speaker was Andrew Szydlo, who is an engaging mix of educator, scholar of the history of science, subject enthusiast, and showman.
The beautiful image above (flames not ghosts!) is one of the many demonstrations in the lecture. This one illustrates how compounds of different chemical elements produce characteristic colours in flames. The lecture made the point, which I'd never thought about before, that this must have been observed for possibly thousands of years, although the substances behind these colours were not understood in terms of elements in the modern sense. That idea has only been around for a couple of hundred years.
To give you an idea of the lecture's scope, it covered, amongst other things: the discovery and recognition of hydrogen as a gas, distinct from air; its connection with water, which gives it its name "Water producer"; ways of producing hydrogen; its use in ballooning and how then R101 disaster destroyed that dream; its use in rocketry that sends satellites up into orbit; its explosive properties when mix with oxygen; the discovery of gaseous diffusion; the role of hydrogen in the revelling of spectral lines; its seminal role in the beginning of quantum physics is; pH and acidity of fruits; and the fact that 78% of the universe is Hydrogen, first discovered by the brilliant Cecilia Payne-Gaposchkin.
To find the YouTube video, just Google The Explosive History of Hydrogen Royal Institution.