The Romance of Modern Chemistry

CHEMISTRY OF THE STARS of spectrum analysis has been the discovery of an element in the sun before it was known on the earth. In 1868 attention was drawn to a conspicuous bright line in the spectrum of the sun’s atmosphere which did not correspond to a line of any element which was then known. Lockyer and Frankland did not hesitate to assert that there must be a new element in the sun, and immediately proceeded to its christening: they called it “ helium11 (Greek, the sun). This is an excellent illustration of the confidence which scientists have in the trustworthiness of the spectroscopic method, a confidence which in this particular case was justified after the lapse of nearly thirty years. In 1895 Sir William Ramsay, working with the rare mineral cleveite, discovered a gas the spectrum of which contains a line coincident with the mysterious bright line already mentioned. This gas is, in fact, helium, and although it is an element of comparative rarity on our globe, it appears to play an important part in the constitution of the sun and stars. Examples of the wonderful detective power of the spectroscope might be multiplied. One might quote, for instance, the discovery of two new alkali metals, rubidium and cæsium, by Bunsen and Kirchhoff, some fifty years ago. These workers, whose names are so closely associated with the marvellous development of spectrum analysis, detected some new lines in the spectrum of a liquid ob- tained by concentrating a certain German mineral water. They boldly concluded that there was in this water some previously undiscovered element, and they forthwith pro- ceeded to search for it. And this element, cæsium, took some finding! Forty tons of the mineral water had to be evaporated and operated on before as much as one- 213